We Run on Iron: Iron Deficiency and Anemia in Runners

In this article, we’ll discuss:

  • The epidemiology of anemia and iron deficiency in runners;
  • Hemoglobin, iron, ferritin, and exercise performance;
  • A couple of cases of anemia in female runners;
  • Why running leads to chronic blood and iron loss;
  • The symptoms and problems of iron excess; and
  • Diagnosing the cause of anemia and treating it, with special guest, Rasmus Høeg, MD, Hematologist.

Case #1

I could not walk even four blocks to get to medical school–it was that bad. I called a cab. I could not breathe. If I walked, I was so short of breath that I felt like I might die.

This was crazy. I was a runner who regularly logged 70 to 80 miles a week without really getting winded. But in the last couple of weeks, my daily runs had been getting really tough. Then, I had barely been able to muster a jog, and if I did, I felt my heart pounding in my chest, even skipping beats. As much as I wanted to believe nothing was wrong, as much as I wanted to avoid going to see a doctor, I realized I could not live like this.

That afternoon, I went directly from class to the walk-in clinic of our medical school. The staff wondered if I was having a panic attack. Well sure, I was scared, but I didn’t think I was having a panic attack. My systolic blood pressure was in the 160s (normally it was in the 90s). Could anxiety do this, I wondered?

The doctor who saw me also wondered about my liver function since I was very yellow-colored. Eventually the blood tests came back and my hemoglobin was 5.8 g/dL (normal is 12.1 to 15.1 in women, as shown in Figure 6 below) and my hematocrit was 19% (normal is 37 to 48% for women). This was profound anemia; severe enough to get me admitted to the hospital. My treating doctors were incredulous, how could an otherwise healthy woman who had not been bleeding (I did not get my period at that time; so yes, you could say this was not healthy) become so severely anemic?

Anemia and Iron Deficiency: Background and Prevalence

So what is anemia? Simply put, it is a condition in which you don’t have enough healthy red blood cells to carry adequate oxygen to the body’s tissues. It can be caused by a number of things including blood loss, lack of iron, lack of B12 or folate, destruction of red blood cells (called hemolysis), or failure of the bone marrow to produce enough blood cells. However, in runners and in the general population, the most common cause is iron deficiency.

Iron deficiency is when the body has inadequate iron. Men typically have 4g of iron in the body while females have 2.5g. Iron deficiency can be diagnosed when serum ferritin is less than 30 ng/mL (Goodnough, 2010), though others would argue one can be symptomatic at levels of less than 50ng/mL. In fact, the diagnosis of iron deficiency is not clear-cut and if a person’s symptoms improve with iron supplementation, they can still be diagnosed with iron deficiency (Schrier, 2018).

[Author’s Note: A number of different laboratory tests, like tests for serum ferritin described above, will be mentioned in this article and their definitions can be found in the Appendix at the end.]

Iron’s largest role is in making and supporting red blood cells (Figure 1), but is also involved the production of neurotransmitters and the protection and function of neurons. It is involved in numerous other biochemical reactions, too numerous to name, and likely more than have been discovered. The most common symptoms of iron deficiency are fatigue, depressed mood, decreased cognitive function, and decreased exercise capacity. On average in healthy adults, men lose 1mg/day of iron and females 2mg/day due to the normal ‘sloughing off’ of the gastrointestinal (GI) tract and also due to blood loss in menstruating females (Clénin, 2017).

Figure 1. The role of iron in the hemoglobin molecule and the number of red blood cells in a healthy person’s artery versus an anemic person’s artery. Image courtesy of Kidshealth.org/en/parents/anemia.html.

A tricky thing to understand is that lack of iron can cause anemia and anemia (due to blood loss) can cause iron deficiency. The former is because if you don’t have enough iron, you can’t make enough red blood cells. The latter is because, if you lose blood, you lose a lot of iron with it. (Again, see the iron in the red blood cell in Figure 1.) So someone who has been bleeding and has inadequate iron intake has double the risk factors for both anemia and iron deficiency.

Importantly to athletes, both anemia and iron deficiency (alone or together) can cause decreased exercise performance and athletes, particularly runners, are at relatively high risk of of both.

Specifically, with regard to anemia, one small study found anemia in 87.5% of triathletes and 31.3% of runners (Coates, 2017). One study found iron-deficiency anemia in 35% of female distance runners and iron deficiency in 50% (Ostojic, 2008). Another study of collegiate cross-country runners found anemia in 2.2% of females and 1.2% of males, but iron deficiency in 33.1% of females and 3.1% of males (Parks, 2017). A third study found an even higher rate in female distance runners of 35% with anemia and 50% with iron deficiency (Clement, 1982). These studies clearly demonstrate that you can be iron deficient without being anemic and that females are at greater risk of both.

Just to put these numbers in perspective, the prevalence of anemia in the United States is estimated to be 5.6% (Le, 2016), which is mostly due to iron deficiency. The prevalence is higher in women (7.6%) than in men (3.5%), believed to be mostly due to menstrual-blood loss. However, these large population studies do not go into enough detail to prove the cause. The prevalence of anemia worldwide is approximately 24%, sadly highest in preschool-age children (60% of children under five years of age are anemic in Africa), and the major cause is insufficient dietary iron (deBenoist, 2008; Semedo, 2014).

Hemoglobin, Anemia, and Exercise Performance

Anemia greatly impacts running performance because inadequate oxygen is delivered to the muscles, including that all-important heart muscle. Specifically, a decrease in hemoglobin level of 1 g/kg was associated with a decrease in VO2 max of 4.4 mL/kg/min (for males it is 4.2 mL/kg/min, and females it is 4.6 mL/mg/min) (Otto, 2013). This is also shown in figures 2 and 3, which show the relationship between hemoglobin level and VO2 max and oxygen uptake into muscles, respectively.

Figure 2. Change in hemoglobin (shown as [Hb]) versus change in VO2 max. Hemodilution is blood letting. Image courtesy of Otto JM, Montgomery HE, Richards T. Haemoglobin concentration and mass as determinants of exercise performance and of surgical outcome. Extrem Physiol Med. 2013;2(1):33. Published 2013 Nov 26. doi:10.1186/2046-7648-2-33.

Figure 3. Hemoglobin level and its relation to oxygen uptake into the muscles in males and females. Image courtesy of Otto JM, Montgomery HE, Richards T. Haemoglobin concentration and mass as determinants of exercise performance and of surgical outcome. Extrem Physiol Med. 2013;2(1):33. Published 2013 Nov 26. doi:10.1186/2046-7648-2-33.

Iron Deficiency

There are three generally accepted stages of iron-deficiency anemia as defined by Mercer, 2005:

  1. Decreased ferritin but normal iron and hemoglobin;
  2. Iron deficiency, which can be seen in decreased iron level, decreased transferrin (a blood protein that binds to iron and transports it throughout the body) saturation, and/or an increase in total iron binding capacity (TIBC); and
  3. Anemia

Iron deficiency also affects exercise performance. Iron deficiency without anemia alone can cause a decrease in VO2 max (Figure 4) (Martens, 2018). This study also showed an increased rate of mortality in patients with iron deficiency, but given they had heart failure, this may not apply to the general population.

Figure 4. Iron deficiency without anemia can lower VO2 max more than anemia without iron deficiency. Image courtesy of Martens P, Nijst P, Verbrugge FH, Smeets K, Dupont M, Mullens W. Impact of iron deficiency on exercise capacity and outcome in heart failure with reduced, mid-range and preserved ejection fraction. Acta Cardiol. 2018;73:115–23.

Iron supplementation in pill form has been found to increase aerobic capacity (specifically VO2 max) in non-anemic but iron-deficient runners (Burden, 2015). Gravican et al. in 2014 also showed intravenous (IV) iron supplementation in runners with low ferritin or iron at the low end of normal caused an increase in VO2 max following supplementation. (Please note that IV infusion is on the World Anti-Doping Agengy [WADA] list of prohibited methods at a certain volume per unit of time.)

Additionally, with regard to IV iron treatment, even if your hemoglobin, iron, and ferritin are normal, IV iron treatment over six weeks was associated with improved mood, decreased fatigue symptoms, and improved 10 x 400-meter times (at two weeks) (Woods, 2014). This study does raise questions in my mind about what the true ‘normal’ level of iron and ferritin are.

Figure 5 below demonstrates nicely the relationship between ferritin levels and symptoms of iron deficiency. (More symptoms have a higher number on the Y axis.) When the patient took iron supplementation, her ferritin rose and symptoms disappeared without any change in hemoglobin or evidence of anemia. For more details about this study and another case example, see Soppi, 2018. Keep in mind that anecdotal reports are not as strong of evidence as a large study with a control group.

Figure 5. The relationship between ferritin, hemoglobin, hematocrit, iron supplementation, and “symptoms” in a patient. S-Ferrit is serum ferritin, B-Hb is blood hemoglobin, E-MCV is estimated mean corpuscular volume (or red blood cell size). Image courtesy of Soppi ET. Iron deficiency without anemia – a clinical challenge. Clin Case Rep. 2018;6(6):1082-1086. Published 2018 Apr 17. doi:10.1002/ccr3.1529.

The Figure 5 evidence supports that athletes with fatigue symptoms, decreasing performance, shortness of breath, and more should thus not only check hemoglobin and hematocrit (and the rest of the blood counts) but also iron and ferritin levels. Given the above epidemiological data, there are likely many athletes in which iron deficiency is overlooked and not diagnosed when they are found not to be anemic.

Why Runners Get Anemic and/or Iron Deficient

Runners go through their red blood cells, and thus also their iron, very quickly. The average blood cell will survive around 120 days in the average (sedentary) adult, but survives only about 74 days in an average runner (Weight, 1991). This is presumably due to the combination of blood loss and mechanical stress causing red blood cell breakdown, as discussed shortly. And that is the great ‘irony’ (so to speak): runners who need adequate hemoglobin to run are very prone to developing anemia. Just days after the resumption of an exercise program, iron stores significantly decrease (Terink, 2018). Despite iron continuously being lost during exercise, there is no innate mechanism to replace it, so sufficient iron must either come through the diet or supplementation (Ottomano, 2012).

The main ways the body uses and loses blood and iron during running are:

  • GI bleeding;
  • Urinary-tract bleeding;
  • Hemolysis or the rupture of red blood cells;
  • Sweating;
  • Inflammation via an increase in the hormone hepcidin; and
  • Travel to higher altitude.

Additional ways runners can have a sudden drop in hemoglobin without bleeding or iron deficiency are:

  • Increase in plasma volume (pseudoanemia) associated with increased training and pregnancy, and
  • Descent from altitude or space.

Let’s discuss these concepts in more detail.

GI-Tract Blood Loss

Bleeding into the stool that is not visible appears to be very common among distance runners. In fact, 85% of participating research subjects in one 100-mile race were found to have “occult” (or invisible) blood in their stool after the finish (Baska, 1990). The one study I could find that looked at the marathon distance (McCabe, 1986) found 23% of participating finishers to have detectable (though not necessarily visible) blood in their stool following the race. Bleeding from the GI tract is believed to either be caused by decreased blood flow to the GI tract or increased acidity directly breaking down the GI tract and causing bleeding (Choi, 2006). It is most likely a combination of both. Additionally, given non-athletes lose 1 to 2mg/day of iron through the sloughing off of their GI tract (Clénin, 2017), I wonder if athletes lose more via this route, though am unable to find a study that has been done to determine amount of iron loss through the stool without any blood in athletes.

Urinary-Tract Blood Loss

In terms of losing iron through urine, there are a number of things that may occur including mechanical trauma in the kidney or bladder wall in addition to breakdown of red blood cells in the bloodstream (hemolysis), which leads to loss of hemoglobin via the kidney (Ottomano, 2012, De DeRuisseau KC, 2002; McInnis, 1998). McInnis in 1998 found that intense exercise was more likely to cause blood in the urine since kidney blood flow is decreased proportionally to exercise intensity, similar to in the GI tract. I have had a number of runners report to me that they have actually seen blood in their urine following a race or intense training session, which is called march hematuria. If the urine is red, this is likely due to an irritated, bleeding small blood vessel and, if the urine is dark, this is more likely the breakdown products of red blood cells and/or muscle cells.


The breakdown of red blood cells appears to occur in many forms of exercise (Ottomano, 2012), but occurs to a fourfold greater extent in running than in cycling (Telford, 2003). The discrepancy between running and cycling is believed to be due to foot strike (Telford, 2003). Indeed, runners wearing more cushioned shoes have less hemolysis (Dressendorfer, 1992). Interestingly, Miller and colleagues in 1988 found significantly greater changes in serum haptoglobin and plasma free Hb levels (both are markers of hemolysis) during downhill running, when compared to an uphill run of equivalent duration and gradient. (Just to be clear, foot-strike hemolysis or the breakdown of blood cells related to foot strike does not occur in the feet, but is a result of the landing impact on the body.)

Sweat-Related Iron Loss

Iron is a constituent of sweat. Sweat iron loss via sweat is estimated to occur at 1% and 3% recommended daily intake of iron per two hours of exercise for women and men, respectively (DeRuisseau KC, 2002).

Hepcidin and Inflammation

Systemic inflammation related to intense training or overtraining and/or muscle breakdown can actually lower iron levels via a hormone called hepcidin (Roecker, 2005; Peeling, 2009). There is a direct relationship between the initiation of an exercise program, decrease in iron level, and increase in hepcidin levels (Terink, 2018). Hepcidin signals for macrophages (immune cells) and liver cells to hide iron away inside of them and also causes decreased absorption of iron from the GI tract. It is important to note that when hepcidin is elevated, ferritin will also be elevated. So, if your ferritin is low or normal, your anemia is likely not due to inflammation.

Travel to Altitude

When people travel to higher altitude, they increase their red blood cell production, thus requiring more iron. Please see Corrine Malcolm’s excellent article on this topic!

Increased Plasma Volume

Increased plasma volume induced by training also tends to lower hemoglobin and hematoctrit. This is called pseudoanemia because it is simply due to an increased amount of plasma, but your actual number of red blood cells stays the same.

Descent from Altitude

Pertinent to many runners is the fact that when you descend from altitude, there is a selective breakdown (hemolysis) of young red blood cells (Chang, 2009). Perhaps less pertinent to runners is that this same effect occurs following return from space flight (Franco, 2009; Rice, 2001; Chang, 2009; Alfrey, 1997). When you descend from altitude (or space), the body is somehow able to sense there are too many red blood cells in the blood vessels (this is called plethora) and selectively kills the young red blood cells. (The exact mechanism, as far as I can find, has not been described.) The young blood cells survive the longest, so it makes sense to get rid of those first. It must have been an evolutionary adaptation for stopping the blood from getting too thick, which can cause strokes or heart attacks via clotting. This may result in normal or even high iron levels with low-normal or lower-than-previous hemoglobin levels.

Expected Sex Differences and Age-Related Changes in Hemoglobin Levels

The normal hemoglobin level is approximately 12 g/dl in women and 13g/dl in men (Murphy, 2014). This appears to be related to sex hormone levels, perhaps most importantly testosterone (Roy, 2017). Testosterone supplementation can actually reverse or ‘cure’ anemia in aging men (Roy, 2017), though the reason it does this is not yet clear and, further, testosterone supplementation is banned by WADA. As you will note, in the table of normals by age in Figure 8, men’s and women’s hemoglobin levels tend to decline with age, but more so for men. Of note, normal hemoglobin levels in boys and girls before puberty is the same and it approaches the same level again in late life.

Despite having lower hemoglobin levels, women are better able to take oxygen up into their muscles due to improved mitochondrial use of oxygen (or respiration) (Cardinale, 2018).

Figure 6. Normal hemoglobin levels by sex and age. Image courtesy of Disabled-world.com/calculators-charts/hemoglobin-iron.php.

Figure 7. Normal hemoglobin levels by sex and age. White circles are females. Image courtesy of Mahlknecht, U. & Kaiser, S. (2010). Age-related changes in peripheral blood counts in humans. Experimental and Therapeutic Medicine, 1, 1019-1025.

Case #2

In the fall of 2017, Kaci Lickteig sustained a pelvic stress fracture and did not run for four months. Prior to resuming her training program, she had her hemoglobin tested and it was normal at 14.3 g/dL. Then, over the course of two months, she gradually started to train and build back her fitness and noticed something was off.

As Kaci explained on her blog: “I started to notice I wasn’t feeling quite right on some of my runs. I felt like my effort was more labored than it should be. I kept telling myself, Oh it’s just because you are getting back into shape. This is normal. Then it happened. I was running one of my standard routes that I have done a bazillion times. As I was running up the slight hill my legs felt like they were completely gassed and in a lactic acid state and my heart started feeling like it was beating out of my chest. I had to stop at the top and regroup. This feeling was a red flag to me. I knew from the past and having been anemic off and on that these were anemia signs and symptoms.”

Figure 8. Kaci Lickteig winning the 2016 Western States 100. Photo: iRunFar/Bryon Powell

Figure 9. Kaci Lickteig’s labs when she was ill. Image courtesy of Kaci Lickteig.

These labs exemplify a classic case of iron-deficiency anemia. Kaci was kind enough to agree to be interviewed for this article.

She describes, “I had not been running (prior to January 22nd) due to my injury and was only lifting weights (no legs involved) and cross training on the bike and Arc Trainer (non-impact activities). Then, starting on January 26, I [tried] to incorporate running. I tested a couple short runs outside and it was too painful yet. So, I was put in physical therapy and could run on the AlterG treadmill starting at 65% of my body weight. In the next couple of months, I increased how much body weight I was able to run at and then tested running outside again.

“It wasn’t until the beginning of March that I was running more consistently. I started to feel like my runs were becoming extremely difficult. I was running, to my standards, extremely slow to start out and even slower as the days went on. Not intentional by any means. I was not in shape, but this was a much different feeling, like I had been sprinting all out. The pain was substantial, like my body was building up lactic acid. My heart would pound so hard I could see it if I looked down at my chest and my breathing was heavy and labored.”

Reading about her experience from home, I had wondered if this sudden development of anemia was related to menstrual-blood loss (just as my doctors had falsely assumed when I was hospitalized for anemia), but this was incorrect. Though she had been getting her period prior to January 22nd, she did not get her period during the two months she developed her anemia. She also added, “During my injury, I stopped taking my iron-pill supplement as I didn’t think I would need it.” She had initially developed iron-deficiency anemia in high school during a self-described time of “under-eating and overtraining.” So this is the case of a young woman with sudden-onset anemia following a return to running, but not due to menstruation.

This left me wondering how often iron deficiency and iron-deficiency anemia in female runners are actually not related to menstruation. Could the increased losses of iron, building up of tissues, and microscopic blood loss be the whole explanation? I wondered if a lack of iron or anemia could, via hormone-level changes, stop a woman from getting her period. I did a thorough PubMed search for these questions and could not come up with any solid scientific research to answer them. However, female runners who do not eat red meat appear to be at remarkably high risk of developing iron deficiency and iron-deficiency anemia. I believe it is a combination of the above-listed factors and, if a female is also menstruating, this would be expected to put her at even higher risk.

Kaci’s primary doctor suspected her anemia was due to foot-strike hemolysis. However, I note that she did not have any lab testing for hemolysis so this can’t be confirmed. Kaci has made the following changes to her diet (and was previously a self-proclaimed “rut eater” who tended to eat the same things day after day) and also did not eat red meat:

  • Eating red meat at least two to three times a week;
  • Using a cast-iron skillet;
  • Changing her diet to include more iron-rich foods such as Cream of Wheat, spinach, black beans, and fortified foods; and
  • Taking an iron supplement twice a day per doctor’s recommendation of ferrous sulfate (325 mg) and vitamin C.

Kaci’s most current labs, from just a couple weeks ago, look greatly improved, however they still show mild iron deficiency:

  • Ferritin (ng/mL) – 17 (normal is 10-154)
  • Hemoglobin (g/dL) – 12.9 (normal is 2-18)
  • Iron (ug/dL) – 37* (normal is 40-190)
  • TIBC (ug/dL) – 510* (normal is 250-450)
  • Transferrin Saturation (%) – 7* (normal is 11-50)
  • Red blood cells (x10E6/µL) – 4.3 (normal is 3.9-5.2)
  • Hematocrit (%) – 45.4* (normal is 1-44.9)
  • MCV (fL) – 107* (normal is 4-94.8)
  • MCHC (g/dL) – 28.4* (normal is 5-36)
  • RDW (%) ­– 17.8* (normal is 5-14.3)
  • Platelets (thousands/uL) – 271 (normal is 140-440)
  • Vitamin B12 – 1377 pg/m

*indicates outside of the normal range

Here is my interpretation of her labs: Low ferritin, iron, and transferrin saturation; MCHC; and high TIBC all suggest continued albeit more mild iron deficiency. Her hemoglobin is within normal, though she did admit to being very dehydrated when she took the labs, which explains her elevated hematocrit, and may have falsely made her hemoglobin level look normal. Her elevated MCV and RDW suggest she is making new blood cells rapidly (likely to compensate for the recent anemia) given her B12 level was normal. She appears to be on the road to recovery, but it’s recommended that she continue with the iron supplementation and dietary changes and have her labs rechecked again in six months.

[Author’s Note: Thank you to Kaci for being so open and sharing her story with us!]

Current Recommendations on Iron Supplementation

The current position statement from the International Olympic Committee (Maughan, 2018) regarding iron and the high-performance athlete includes the following:

  • “Suboptimal iron status may result from limited iron intake, poor bioavailability and/or inadequate energy intake, or excess iron need due to rapid growth, high-altitude training, menstrual blood loss, foot-strike haemolysis, or excess losses in sweat, urine or faeces (Thomas, 2016).”
  • “Several measures performed simultaneously provide the best assessment and determine the stage of deficiency. Recommended measures: serum ferritin, transferrin saturation, serum iron, transferrin receptor, zinc protoporphyrin, haemoglobin, haematocrit and mean corpuscular volume (Gibson, 2005).”
  • “Athletes who do not maintain adequate iron status may need supplemental iron at doses greater than their RDA [recommended daily allowance] (ie, >18 mg/day for women and >8 mg/day for men). Athletes with iron deficiency require clinical follow-up, which may include supplementation with larger doses of oral iron supplementation along with improved dietary iron intake (Thomas, 2016).”
  • “High dose iron supplementation should not be taken unless iron deficiency is present.”

Anemia Treatment

Before you embark on taking supplemental iron, I do recommend both men and women have their complete blood count (CBC) and iron panel tested. However, eating a diet rich in iron is likely a safe thing for runners to do.

For anyone who tends to be iron deficient, it is helpful to know which foods are rich in iron. These foods include red meat, shellfish, spinach, liver, legumes, pumpkin seeds, sesame seeds, quinoa, turkey, broccoli, tofu, dark chocolate, oats, sesame seeds, coconut milk, and fortified cereals.

If you are found to have any of the stages of iron deficiency, you may also choose to supplement with a maximum of 325 mg ferrous sulfate three times a day. IV iron can also be considered in more severe cases of iron-deficiency anemia.

However, when it comes to iron absorption, there is a big difference between heme and non-heme iron absorption. Heme iron, or actual hemoglobin (in other words, blood), only comes from eating animals and has an absorption rate as high as 35% while non-heme iron (all non-animal forms of iron) has an absorption rate as low as 1%. However, consuming heme iron has been linked to an increased risk in colon cancer (Bastide, 2015), breast cancer (Diallo, 2016), and all-cause mortality (Etemadi, 2017).

If you do not wish to eat meat or heme iron, you can also increase your iron absorption by eating vitamin-C-rich foods or taking vitamin C when eating (which increases iron absorption by up to 300%!) However, vitamin C actually converts iron into a more potent pro-oxidant (argh, nutritional medicine is just never simple), but if you are severely iron deficient, I would still agree with adding vitamin C to increase absorption. Avoid drinking coffee (I guess it’s the phenolic acid and not the caffeine) and tea with your meals (which can decrease absorption by up to 90%). Consider cooking in a cast-iron pan, which can transfer two to three times more iron to the prepared food than conventional cookware. Finally, antacid use and h. pylori bacterial infection, and any form of chronic diarrhea, can significantly reduce the absorption of iron.

Iron Excess or Overload

But while iron for the iron-deficient person is good, too much iron for the non-iron deficient has serious risks. An interesting thing about iron that sets it apart from most other minerals and vitamins is that the human body has no built-in, automatic mechanism of eliminating it, unless you bleed regularly. Iron supplementation in those with already-adequate iron stores can result in symptoms that may begin with vomiting, diarrhea, and abdominal pain, and progress to hemochromatosis (systemic disease caused by iron overload) and liver failure (Mettler, 2010). Iron, rather than being an anti-oxidant is actually a pro-oxidant, meaning it causes tissue destruction, can cause diabetes, heart disease, bronzing of the skin, and many other disorders when at a high-enough levels. Mice with iron overload have also been found to have decreased exercise performance, and it was felt iron overload may play a significant role in skeletal muscle atrophy (Reardon, 2009). Iron excess has been found in 19 out of 127 (15.0%) male runners and 2 out of 43 in females (4.7%) (Mettler, 2010), which sounds to be related to excessive/unnecessary supplementation.

Figure 10. Signs and symptoms of iron overload. Image courtesy of Kimberly Taranowski.

Case #1 Continued

While still in the hospital, I was diagnosed with both celiac disease (a surprisingly common cause of iron-deficiency anemia) and clostridium difficile (a bacterial infection, rare at that time, which causes loose stools and malabsorption). I gave up wheat and was treated with the antibiotic metronidazole (Flagyl). A few weeks after being discharged from the hospital, I underwent an endoscopy and colonoscopy (both of which were normal) to determine if there was any obvious GI bleeding occurring. When a bone-marrow biopsy was recommended by my hematologist, I suggested I try eating liver for dinner every night for one week and come back. After that one week, my hemoglobin was normal again. Granted it had been steadily rising prior to that, but it did not come up into the normal range despite weeks of iron supplementation until I changed my diet. This has always intrigued me and, when writing this article, I finally may have found the explanation. (See heme versus non-heme iron above.) Since this hospitalization, I have had my hemoglobin and hematocrit checked a few times and they have always been normal, however, I have not had my iron tested. A couple of weeks ago while beginning to do research for this article, I started to take 325mg of ferrous sulfate twice a day and I have to say I am pleasantly surprised with my running times and overall energy level. Since I am a pesco-vegetarian with a pretty demanding training schedule, I now realize how high of risk I am for iron deficiency. Now I just need to make an appointment to get my iron labs tested so that I practice what I preach!

Anemia-Treatment Discussion with a Hemotologist

At this time, I would like to bring in my ‘in-house’ (he is my husband) hematologist, Rasmus Høeg, MD, Assistant Professor of Hematology and Oncology at UC Davis School of Medicine.

iRunFar: Can you comment on Kaci’s labs and whether or not these are indicative of hemolysis? To me these look like typical iron-deficiency labs and, given she did not menstruate between the time of the two labs, could you postulate what the most likely cause would be? Should she have additional testing? Do you recommend that athletes like Kaci who tend to get iron-deficiency anemia take iron supplements to prevent its development (even if they are not currently anemic)?

Rasmus Høeg: I agree that the labs are all very suggestive of iron deficiency. I don’t know what else it could be. Foot-strike hemolysis or hemolysis in general would not be expected to cause that degree of iron-deficiency anemia so quickly (though hemolysis lab tests should be ordered if this is suspected). Now, the next question in a case of iron-deficiency is always, “Where did all the iron (blood) go?” Doctors will often blame heavy periods or, in the absence of heavy periods, worry about GI or genitourinary blood loss. As you know from your own case, the next step is often to order a colonoscopy and/or upper endoscopy.

Kaci’s sudden development of anemia is unusual. But of course anemias don’t read textbooks. I suspect that she was living with a mild degree of iron deficiency during her more sedentary months. In other words, she was able to produce enough hemoglobin to stay non-anemic. However, once she started exercising and her demand for hemoglobin increased, she was unable to keep up with production. Honestly, elite athletes like Kaci do not really adhere to normal rules of medicine.

I think it makes sense for Kaci to take supplemental iron, at least if she can tolerate it. If she were my patient, I would order a CBC with iron studies every so often (maybe every six months) and see where things are at. By the way, during her more serious iron deficiency, some doctors would have considered IV iron as a treatment of her anemia.

iRunFar: Is there an indication for using IV iron to treat iron-deficiency anemia in your mind and, if so, what?

Rasmus Høeg: The usual indication for IV iron is significant iron deficiency in a patient who is unable to tolerate oral iron. But there is no clear cutoff for when to give IV iron. Most patients do not like taking oral iron. For example, few patients are able to take the full dose of 325 mg ferrous sulfate three times daily. So what do you do with a patient who has some improvement with oral iron, but who is still anemic and is unable to increase her oral dose?

IV iron can sometimes work very quickly and is very effective. I think one reason IV iron is not used more frequently is that it carries the stigma of being associated with nasty infusion reactions. It is true that the ‘old’ form of IV iron, called iron dextran, can cause an anaphylactic reaction when it is infused. It requires that you give a tiny test dose and watch the patient for a while, before giving the full dose. Stuff like that worries doctors, of course.

There are many new formulations of IV iron that have almost no infusion reaction. But then some insurance companies will insist you try iron dextran first etc. In fact, like all IV medications, there is the added insurance hassle that doctors don’t like to deal with. All in all, IV iron takes a little bit of getting used to from the doctor’s standpoint.

If I were a patient/athlete being offered IV iron for iron deficiency, I would definitely say yes.

iRunFar: Are you aware of anyone besides those with the disease hereditary hemochromatosis (a disease where too much iron is absorbed and stored) developing iron excess through diet alone and without taking supplements?

Rasmus Høeg: First of all, most patients who develop significant iron overload do so because of frequent blood transfusions. Blood, as you know, has a lot of iron in it. If a person has a disease with a need for ongoing blood transfusions, iron overload will invariably develop. This can be a huge problem and these patients should avoid all iron supplementation.

Good question about hemochromatosis. The problem is that hereditary hemochromatosis comes in various forms. There are two main hemochromatosis mutations that are passed down in families and they can combine in various ways to increase the risk of clinical iron overload. Something like 10% of people with European ancestry are carriers of hemochromatosis and are at a higher (yet still very low) risk of developing clinical iron overload. If such a low-risk person does develop iron overload despite all odds, you would wonder if this was caused by excessive iron supplementation.

I personally think a person without any hemochromatosis gene would have to be pretty zealous with his iron supplementation to develop iron overload. And, yes, that zealot would have to be a man, because men generally develop iron overload much more frequently than women due to their lack of periods.

Easily available gene panels like 23andMe test for hemochromatosis as well as carrier status, by the way.

iRunFar: Do you think the recommended daily intake of iron should be higher for runners than sedentary adults?

Rasmus Høeg: For a runner without any history of iron deficiency, I would not recommend taking supplemental iron. People hate taking iron. It has a lot of GI side effects, such as abdominal pain and diarrhea or constipation. Some supplements are better tolerated, sometimes because the amount of iron in it is very low, and sometimes because everyone tolerates things a little differently. A few exceptions, in which I think taking ‘preemptive’ iron are menstruating or pregnant women, or people moving to altitude to train. These situations lead to a higher demand for iron.

A related question might then be, who should have a CBC and iron studies checked? I think any unexplained drop in performance, any symptoms of anemia, pregnancy (which also has an increased prevalence of both iron deficiency and anemia), heavy menses etc. would justify these tests, for reasons you have outlines above.

iRunFar: Do you have any tips for someone who would like to get their hemoglobin into the upper end of normal if their iron stores are full/normal?

Rasmus Høeg: No specific tips. In fact, most athletes will have hemoglobin concentrations in the lower end of normal due to a higher plasma volume. So we should not expect to see high levels of hemoglobin in most athletes. Of course, altitude training and substitutes such as altitude huts and tents can produce the effect in some runners. And, as we know from all the doping we have seen in professional endurance sports, erythropoietin (EPO, a protein secreted by the kidney that stimulates bone marrow red blood cell production) supplementation is very effective in raising hemoglobin. [Author’s Note: Of course this is a WADA banned substance!]

So for most runners, I think time worrying about hemoglobin levels is better spent elsewhere. However, the studies you refer to above, in which performance increases with iron supplementation in patients without overt anemia, are very interesting. I think they show that some athletes have a hemoglobin in the low-normal range, but their bodies ‘want’ the level to be a little higher. It is not easy identifying these patients, but it would require all the blood tests mentioned above, and perhaps an EPO level (a very elevated EPO level would show that the body is ‘trying’ to raise the hemoglobin level).

iRunFar: Are there any additional remarks you would like to make about testing for iron deficiency and anemia? Are there additional tests that would be helpful?

Rasmus Høeg: I think the best way to look at iron studies is to realize that not one test is the perfect test. Well, in fact, that is incorrect. The ‘gold standard’ to diagnose iron deficiency is a bone-marrow biopsy, where a piece of bone marrow is examined for iron content. The bone marrow is where red blood cells are produced, as some readers may know. The problem is that bone-marrow biopsies hurt, so they are usually only done when a cancer of the bone marrow is suspected.

Other tests that may be useful to diagnosed iron-deficiency anemia are:

  • Reticulocyte count – A measure of the body’s production of red blood cells. Should be low in iron-deficiency anemia.
  • Soluble transferrin receptor – A measure of the body’s attempt to get more iron. Should be high in iron deficiency.
  • EPO level – A measure of the body’s attempt to raise hemoglobin levels. A fun to test to get back, but normal levels are not well-defined. Should be high in most types of anemia, but could also be elevated in states of low iron and low-normal hemoglobin.
  • There are also some hints in the way the red blood cells look in the microscope that give clues about iron deficiency, but that’s probably too far in the weeds for this article.

That’s a lot of tests! Interpreting anemia can sometimes be like reading tea leaves, and often the doctor will simply start a treatment based on an educated guess and follow the patient closely.

iRunFar: Is there anything else you think readers of this article should know about iron deficiency, iron-deficiency anemia, or anemia in general?

Rasmus Høeg: I think most men can live a long life and not worry about iron deficiency. In fact, if they are diagnosed with iron-deficiency anemia, the least of their worries should be how to run faster. It should be, “Where am I bleeding from?!” In many cases, iron-deficiency anemia in a man should elicit a colonoscopy, upper endoscopy, and urinalysis to look for the cause of blood loss.

For menstruating women, for all the reasons mentioned above, it makes sense to check iron studies periodically, especially at times of fatigue, anemia symptoms, pregnancy, heavy menses, and more.

Call for Comments

  • Are you a runner who has developed anemia due to a cause other than a known bleeding source?
  • Do you have puzzling labs from an anemia work-up that you would like to share?
  • Have you developed iron excess from supplementation or diet? Did you have symptoms from this?


Lab-test definitions:

  • Ferritin (ng/mL) – Stores of iron in the liver. Low in iron deficiency. High during inflammation.
  • Hemoglobin (g/dL) – Amount of hemoglobin (the oxygen-carrying molecule) in the blood. Low in anemia.
  • Iron (ug/dL) – The element and its amount per unit blood.
  • TIBC (ug/dL) – Total iron-binding capacity, or the amount of room there is for extra iron. This is high in iron-deficiency anemia.
  • TS (%) – Total iron saturation or the percent of iron stores that are full.
  • Red blood cells (x10E6/µL) – The amount of blood cells per unit blood.
  • Hematocrit (%) – The percentage of blood cells per unit blood. Low in anemia.
  • MCV (fL) – Mean corpuscular volume, the size of the red blood cell.
  • MCHC (g/dL) – Mean corpuscular hemoglobin concentration or the amount of hemoglobin per red blood cell. Low in iron deficiency and vitamin B12 deficiency.
  • RDW (%) – Red blood cell distribution width, the percent difference in the sizes of red blood cells. Increased when lots of new blood cells are being made.
  • Platelets (thousands/uL) – Number of platelets per unit blood. Unrelated to anemia and iron deficiency.


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Tracy Beth Høeg MD, PhD

is currently a Sports and Spine Medicine physician at Mountain View Rehabilitation in Grass Valley, California, and an assistant professor at UC Davis. She completed residency in Physical Medicine and Rehabilitation at UC Davis and a PhD in Ophthalmology at The University of Copenhagen. She is a Danish-American double citizen who ran for the United States at the 2013 IAU Trail World Championships and for Denmark at the 2018 WMRA Long Distance Mountain Running Championships. She is married to Dr. Rasmus Høeg and they have two sons.

There are 37 comments

  1. Lou

    Very thorough article. As a PA who is studying for my recertification this was a great refresher.
    One question. Your article uses two examples of females who are not menstruating who become anemic presumably from the effects of running alone. However in regards to males who become anemic it appears (at least how I understand the article)less likely to be from running alone. Is this purely because of testosterone?
    Personal anecdote. I’m a 35 year old male who has had iron deficiency anemia in the past without any clear explanation. This was 15 years ago and it was never worked up. The only reason I found this out was because I was donating plasma during college. My H and H was 9 and 27. I took some iron and it went away. I was so ignorant at the time I never really thought about it. Perhaps it was from running?

    1. Tracy Høeg

      Lou, great question. I do not know why women are iron deficient more often than men – thought it COULD simply be due to menstruation, though as Kaci’s and my case point out, it does not always have to be due to menstruation. Maybe the percent of non-menstruating female runners who are iron deficient is the same as male runners. I do not know. This study has not been done to my knowledge. But if there is a difference, maybe it is dietary (maybe women eat less red meat in general?), maybe it is testosterone or maybe it is some other factor we have yet to discover.

      But to answer your other question – if your hemoglobin was 9 it definitely could have been iron deficiency anemia, especially if it got better with supplementation. I don’t know enough info to “blame” running alone, but if you were otherwise healthy and not bleeding from anywhere, then maybe it was.

      I apologize I don’t have straight-forward answers, but I have learned better than to jump to conclusions when it comes to human physiology!

  2. SageCanaday

    very well done! This is the most comprehensive article I’ve seen on iron deficiency and anemia and runners. Extremely informative and thorough!

    Glad you included this part: “However, consuming heme iron has been linked to an increased risk in colon cancer (Bastide, 2015), breast cancer (Diallo, 2016), and all-cause mortality (Etemadi, 2017).” Traditionally people seem to think that red meat (heme iron) is a quick solution. I’ve run with many guys that ate red meat all the time and they’d still have all these problems with iron. There is that oxidation factor of course. I think it is good that people are realizing plant-sources of iron can be very effective..esp with sources of vitamin C from things like fruits.

    Also glad you got in the mention about EPO as a PED as well: “And, as we know from all the doping we have seen in professional endurance sports, erythropoietin (EPO, a protein secreted by the kidney that stimulates bone marrow red blood cell production) supplementation is very effective in raising hemoglobin.”

  3. Katie

    Outstanding article! You mention athletes that move to altitude to train a few times, but what about those of us who just live, run, bleed and sleep at high altitude year round? Is there any further information we should know?

    1. Tracy Høeg

      Katie, it is generally thought that the normal hematocrit and hemoglobin concentrations are higher at altitude than at sea level, but it is actually quite complex as some ethnicities (Nepalese) seem to not have a change in hemoglobin concentration until very high altitude. If a person ascends and descends often, there is increased iron requirements when ascending to altitude. I am not sure if more iron is required when you live at altitude all of the time. I think the body equilibrates to not needing more than the general population, but I am not sure and can’t find a good resource on a quick perusal of the literature.

  4. Carmen Micsa

    Outstanding article and very well-researched. I experience occasional bleeding after tough runs and after each marathon,and I am a little iron deficient, but only borderline, so this article was extremely informative. Thank you so much!

    1. Tracy Høeg

      Carmen! Great to hear from you and thanks for sharing your experience. If you are always borderline deficient in iron, it might be worthwhile to do a low dose regular supplement if you want to improve your running times. I can’t guarantee anything, but it might increase your energy.

  5. jumpinjacks

    H.pylori was the culprit for me, my ferritin was a level 4 for years even with iron supplements. I became desperate to find the cause of the anemia and ordered an at home test for h.pylori (no prescription needed to order this test). It came back positive. At this point I went to the doctor for the prescription for triple therapy antibiotics. After treatment my ferritin went up to 44 (Vitamin B, D, etc. also drastically increased)! H.pylori occurs in 20% of Americans and much greater in some other countries. I am pretty sure I got this while traveling abroad years ago and drinking bad water. H.pylori is carcinogenic and leads to an increase to stomach cancer so there are many reasons to get tested. Here is a good resource as well http://www.irondisorders.org/Websites/idi/files/Content/854291/hpylori.pdf. Thank you for this great article!

    1. jumpinjacks

      I am a female with these ferritin numbers (I am pointing this out because I realized my user name may cause some people to think my name is Jack).

    2. Tracy Høeg

      Jumpinjacks – thank you so much for sharing your experience with h. pylori and for sharing the link. I did not realize until I read further that h. pylori actually lives off of directly “eating” iron. This may definitely be part of the story in many runners who develop iron deficiency if the prevalence truly is 20% in the US – that is high! I also didn’t realize that the more iron you feed h. pylori, the higher the risk of cancer. This would have been a great addition to the article. Thanks for bringing this up and clarifying a topic I did not have a very good understanding of.

  6. Glen

    Great article! This was very helpful. I am an older male runner who was diagnosed with anemia a few years ago and prescribed oral iron supplements as described in your article, which seemed to help. I had a negative colonoscopy at that time. The doctor suggested my lack of iron in my diet along with running ultramarathons was the likely cause (I do not eat meat) since there was no discernible GI bleeding.
    It has been several years and my energy levels seem low again so this article suggests I should have my blood iron levels checked again.

  7. Greg Woodward

    I am 33 yr. Old male vegetarian ultra runner. I was recently found to be anemic with iron deficiency. The above article I was experiencing pretty much all of the above symptoms. I was running 60-80 miles per week, my hemoglobin was a 11 my iron results were pretty much non existent. I had zero signs of blood loss.
    After a little less than 90 days of taking Vitamin C, and Ferrous Sulfate 325mg tablet twice a day(thankfully no stomach issues from supplement) and trying to eat healthier in general and never adjusted my training runs really, I got rechecked.
    Hemoglobin is 17.4 and iron 46, I really feel so much better If it wasnt for my yearly physical I would have never known I was anemic or had a issue, I just assumed I was tired from normal training.
    So I will continue to supplement Iron and will get rechecked in 6 months. I had never known that this could be a issue with runners or a diet issue it absolutely can, I was eating like a lazy vegetarian. If anyone would like to see my before and after lab numbers im happy to share them, thanks for a great article.

  8. Sarah W

    Tracy and hematologist husband,

    I take an iron supplement that uses a ferrous succinate form of iron. It also contains B12, liquid liver fractions, and chlorophyllin. The formulation is supposed to help with absorption. I have been using this product for years to maintain iron levels.

    I was wondering if you could speak to the difference between ferrous sulfate iron and ferrous succinate iron and if there is a benefit to one or the other. I was also wondering about absorption with drinking morning coffee. Should iron not be taken after drinking coffee and how long after drinking coffee/caffeinated drinks should we wait to take iron so that it gets absorbed properly.

  9. Lorraine Wilkinson

    Very interesting article. I have personally been anemic as a child and in later life have experienced issues that I could not understand. I am a long distance runner with multi stage races too. 2 years ago I started to feel short of breath, tired and no energy sometimes having to stop and walk part of my run. I took weeks off from running thinking i was running too much. I had labs taken and sure enough my ferritin was on the floor. So I took supplements for a while but not really any change so had 3 iron infusions. I then felt improved but still have to take ferritin and ferrous sulphate supplements. My Doc has done all the tests and found no bleeding or reason that my ferritin keeps dropping. After reading this article I understand what is happening to me too. I will pass this onto my Doc he will love the read too.
    Thank you

  10. Delia

    This is a fantastic article – thank you Tracy and Rasmus for getting into the weeds for us.
    I have never been diagnosed with anemia or iron deficiency, but I had two experiences with some of the symptoms, though not coinciding with an increase in running. I’m a female omnivore (adventurous and varied diet), with light menstruation like clockwork.
    I had been living in Sri Lanka in my early 20s and had switched to a local pescatarian diet by necessity. About 4 months into my stay I developed a feeling of profound exhaustion with brain fog and a general lack of “go-getter-ness.” After getting my hands on some broad-based multivitamins and a single meal of red meat, I felt better within a week. I couldn’t test the longevity of this solution because I went home after 5.5 months. Fast forward two years and I was back in Sri Lanka, similar diet as before, and the symptoms came back right around the 4 month mark. Fool me twice, shame on me – I had to actually start taking the iron-containing multivitamins I brought with me – I’d been ignoring them because they tasted icky. My diet was full of dark leafy green vegetables in both instances, by the way. (no cream of wheat or black beans, though – mostly lighter legumes) I guess I know what I have to do if I want to switch to a plant based diet.
    I’m curious about the cast-iron pan thing. Have there been tests done on the actual food cooked in them to see if it contains more iron, or is that just a plausible connection?

  11. Lydia Blythe

    This is a fantastic overview of iron deficiency in runners. I was diagnosed with iron deficiency anaemia a year ago and this article sums up exactly everything I have been through. My one question would be concerning the link between RED-S (overtraining and under eating, along with amenorrhea) and developing iron-deficiency anaemia. Any more information on this would be very helpful for me.

    Also, how long does it take to fully recover as an athlete from low ferritin, haemoglobin and haematocrit? Of course the levels can return to normal, but is there a catch up game the rest of your body has to play?

  12. Denzil

    After experiencing a feeling of fatigue I’ve never felt before, I recently had my iron and vitamin D levels checked, and both came back “on the low side of normal” according to my Dr. Specifically, my ferritin levels are at 14ng/mL (Iron and hemoglobin are normal), which is well bellow the normal range cited in this article. I asked my Dr. about supplementation, and he didn’t recommend it at this time. I had already been supplementing vitamin D for 3 weeks, since I suspected that was low due to living in the PNW and it being winter, so I can only imagine how low it was prior to that. The vitamin D supplementation has made an improvement in the fatigue feelings, but now I wonder how much better I could feel with raising my ferritin levels, or even how long they’ve been low. Any advice?

  13. annoynomous

    hello everyone
    i know i am late but i just saw this post such an amazing post so informative thanks for doing this
    i fit just the description you asked to comment
    i am a 18 year old male runner(vegetarian since birth) before which i was a very active soccer player(since very young) and by that i mean that i mean there were periods of time when i played over 3-4+ hours everyday.
    for some reason i switched over to running. i would consider myself above average runner. i never felt breathless and tired at any point in my life thus far which is why what was about to follow was surprising.
    i had to do blood check for some reason
    and shockingly my ferritin was 6(20-300)(the numbers in brackets are reference for the lab as i did another test after this in a another lab) and hb was 12(13.5-18) it was very surprising because after some googling i found that at this level you are supposed to feel breathless just walking yet i was running 6 times a week not really that breathless. the only symptom i could think of is when i try to run harder than usual my legs would feel very heavy right from the start
    so i was given iron pills after three months i went for another check up this time
    ferritin 36(47 -450) hb 14(14-18.5) reference range is higher because different lab
    so while my values increased i felt absolutely zero difference i feel just as active i have been asked to come for another check up two months from the time of last check up(this time without taking any pills) which is two weeks from now is it likely that my values would have dropped again. i had paused running for 2 months because of some work. i just recently started running again went for 8km to begin with felt just like before although it was slower.
    thanks for reading . please feel free to comment is it normal to have anemia and not have any symptoms and how quickly will the values drop after you stop taking pills
    thanks for your time i really appreciate this tried asking around in other websites no one responded thanks :)

    1. Tracy Hoeg

      Hi Anon,

      Yes, it is normal to not have symptoms when it develops gradually. In fact most people won’t notice symptoms with a Hgb of 12. It is good to have your low ferritin treated for your bone health and good to have the anemia treated for your heart. I would strive to keep your Hgb and ferritin in the normal range (as you sound to be doing). Also, your levels drop again, you should be checked to make sure there is no GI bleeding causing it.

  14. Anonymous

    Hi and thank you for writing this article. I am a 4x marathoner (female,
    33), ran a PB at Boston this spring (3:01) and had a great training cycle leading up to that (just regular marathon training fatigue). Last few weeks I’ve felt quite low energy, and finally decided to take it upon myself to get a blood test. My ferritin came in at 8ng/mL…hemoglobin was slightly low but in range. Other indicators were high cholesterol and triglycerides- which seems very strange as I rarely eat red meat, maybe 2-3 eggs per week, and otherwise very healthy. I’m seeing my doctor ASAP, but any other advice for what to ask and look for would be welcome. I’m trying to assess how concerned I should be with such a low ferritin number and these other indicators…

  15. Amy

    I have run 11 marathons and 20 half marathons over the past 10 years or so, and run 30-40 mpw when not in training and 50-60 in the thick of training. I experienced severe fatigue, headaches, muscle and joint pain after running 2 marathons in a 3-month period. PCP suspected anemia and labs show Hgb 13.7, Hct 41.7c MCV 102.9, Ferritin 22, Total iron 241, Iron Sat 68%. She is stumped. I have general exercise intolerance as I never have before. Muscles feel dead when recruit them for even a slow jog, plus chest discomfort if I run long or in the heat. I have had ferritin at 30 in 2016 and symptoms similar, but milder, discovered by my dermatologist checking for the cause of hair loss. He didn’t check other open studies. Once ferritin was above 45 taking iron supplements over 3 months, my hair grew back and fatigue resolved. But now my blood shoes high total iron and iron sat. I eat a healthy diet with lots of fruits, vegetables, whole grains, and lean meats. Any ideas?

    1. crawdady

      Check your B12 and Vitamin D levels. Low B12 presents as anemia. Vitamin D important for a host of bodily processes, and involved with iron status specifically. Also would not hurt to check for H. Pylori.

  16. crawdady

    I feel the medical profession and hematologists in particular are failing endurance athletes when it comes to IDNA – Iron deficiency non-anemia. We had a hematologist say with a straight face “your ferritin of 14 couldn’t possibly be the cause of your fatigue” even though he would have recommended infusion if the ferritin was 12. They think that if you have virtually any iron in storage (ferritin) and your hemoglobin is in the normal range, then there are no issues.

    But any endurance athlete who has been through this and almost every collegiate track / cross country coach will tell you that 45-50 ferritin is their minimum, otherwise you are impaired. There is some (non-definitive) research that suggests that ferritin plays another role in maintaining our endurance. Pamela Hinton (now Bruzina) at the U of Missouri is at the forefront of this and has written a great paper entitled “Iron and the Endurance Athlete” 2014. Unfortunately, all but the abstract sits behind a paywall. She was kind enough to forward me a full copy.

    It is hard for me to fault hematologists who have cancer patients fighting for their lives when my issue is that my daughters simply can’t run as fast as they should. Asking doctors to deviate from the accepted norms for ferritin levels is a no win situation when it comes to malpractice lawsuits. I have searched high and low for doctors that are focused on endurance athletes and “get it” with regards to the impact of low ferritin on endurance performance. So far, no luck.

    1. Tracy Hoeg

      crawdady, Interesting comment. First, I am the doctor (MD, PhD) who wrote this article and you found me and I agree with you and my husband is a hematologist who agrees, too. So there are doctors interested in this topic who agree with you! :-). And a ferritin of 14 can absolutely cause fatigue in an athlete (or non athlete!). In terms of treating the problem, though, you actually don’t need a doctor and can buy iron supplementation over the counter. But point well taken that there is not a lot of awareness in the medical community that low ferritin can cause fatigue with normal hemoglobin and hematocrit. Thanks for the comment!

  17. crawdady

    And thank you for your response. I later felt my “failing” comment was a little harsh. We are in a situation where supplementation is not working after 2 years of 2 daughters supplementing non-stop (we have tried everything: heme, non-heme, poly saccharide iron complex, with vit C, morning, or evening, empty stomach or with food, no calcium). So we are quite frustrated with the situation.

    Also, the interplay between all of the supplementation factors listed above with the body’s production of iron-blocking hepcidin (both from the liver and the spleen (glucose driven)) makes a very complicated situation even more-so. Taking a supplement raises hepcidin, which blocks absorption. So does working out, getting an infection, and as already mentioned – consuming glucose. So working out (running) and taking a supplement actually works against absorbing iron.

    One daughter has celiac disease, so gut absorption is already compromised. She redshirted her freshman college XC season due to ferritin at 14. At least here we understand that Celiac is part of the problem.

    But for my other daughter, if feels like if she stands on one foot, facing north, with her head cocked at a 45 degree angle while humming the national anthem on a Tuesday at 3:45pm, she might get a modicum of absorption. Miss any of those variables, and her ferritin stays low and sabotages an entire season of racing. In the two years since she we found out her ferritin was an issue, she has never run a race with ferritin above 20. She is a HS junior being recruited by high level colleges, but she if fighting with one hand tied behind her back.

    So when a hematologist (who we waited 4 weeks to see) says low ferritin couldn’t possibly be the reason for her fatigue, I want to scream.

  18. Tammie

    So glad I came across this article. I have been fighting low ferretin levels for several years now. I eat plenty of red meat. My issue appears to be malabsorption but no doctors seem to know why. I’ve tried every oral iron available and cannot tolerate it nor does it seem to help. I get a series of 4 iron infusions and have to take Benadryl and Pepcid at each one to reduce an allergic reaction. I feel great for a few months as my iron is spiked and then start feeling worse and worse until my iron levels are low enough to start the whole process over. Here is my question — I am not a distance runner. I run 4-5 miles per day 5-6 times per week. Do you think I fall into this category? Where my iron deficiency is due to running?

  19. Wyatt Crowther

    I am an 18 year old distance runner. I have been struggling with low iron and anemia for two years. I have been seeing doctors and taking supplements for this long. Last year I had a CBC and my ferretin came back as a 7. I took iron in the summer and kept taking it throughout cross country season. However, right at the start of the season I began to feel anemic again. I went to the doctor and they did countless tests on each but didn’t have an answer. I started training for track by running about 50 miles a week. This is normal. I felt decently good until about two weeks age when I started feeling the symptoms again. Around this time it started getting much warmer. Could this be a cause? I do everything I can to absorb the max amount of iron but nothing works. Please help!

  20. Tracy Hoeg

    Wyatt, you can definitely lose iron in sweat. Are you certain your symptoms are from iron deficiency? If you are, then do you eat red meat? If not, I would add this to iron supplements. Also, if you iron is below normal you should see a doctor to make sure you do not have occult bleeding (though that would be very unusual at age 18!!) or some other cause.

  21. Mary Bornstein

    Thanks for your article. My daughter is a competitive high sophomore cross country runner and has been battling anemia. The first year her iron levels were low as they were 6 months ago. She started taking iron and her times dropped immediately. Started feeling fatigued again and now her ferritin is a 5 but her iron is in range just on the low range. We are thinking of having her go gluten free because her brothers are intolerant to gluten. What are your thoughts?

  22. Mik

    Is there a general mileage range where iron deficiency and/or anemia is likely to come from running? Also, is it normal to require more iron supplementation over time to maintain the same iron levels even if mileage/activity isn’t increasing? I first found out I had low iron in 2016 with Hgb 10.3 and started taking 65mg iron a day and was fine for 2.5 yrs of running XC and track. During that time, I increased mileage to 40-45 mi a week and have not gone over that for max mileage since, yet for the past year my ferritin keeps dropping under 20 and I start having symptoms every few months. Each time I just increase my iron by adding another tablet to the daily, but I’m under 20 ferritin a few months later even with increased iron supplements. Any thoughts much appreciated. (side note I’ve never naturally gotten a period in my life and I’m 18 so menstrual blood loss shouldn’t be an issue?? last time I took meds that induced a period was 9 months ago and the few times I’ve done that bleeding has been low to average)

    Thanks so much for writing this article though! I know a lot of my teammates and other girls I know from the wider competitive running community have had issues with iron and this article is super thoughtful, thorough, and informative!!


  23. James Kenny

    I am a 63 year old male runner.I have ran 34 marathons and numerous other races since 1982. In 1999 my iron levels went off the scale.I had not been running that year.My levels were low for at least 6 months.until I finally got a blood test.I was given a blood transfusion.I had 2 endoscopes and 2 colonoscopies. No evidence no evidence of bleeding and I am not coeliac.For the last 22 years my blood levels have remained normal.I have taken no iron tablets or supplements as advised as I never found out what caused it.I have ran a marathon every year since 2001 all with no problems.I got my blood tested every year but forgot to get it tested last summer due to pandemic.I did a virtual marathon end of October at very easy pace, took 2 weeks off after.Then resumed very easy running 7 days per week after rest.?In January 2021 felt my runs very difficult despite easy pace.I got my blood tested in early February 2021 my haemoglobin had fallen to 9.1 and a week later to 8.1.My ferriten was 2.I got 2 iron transfusions , my levels are increasing.I had an endoscopy and colonoscopy last week.My colonoscopy was clear.The stomach scope showed some signs of gastritis/ inflammation.I am taking panto flux for the month and will have a follow up CT scan .I have no stomach pains or any discomfort whatsoever. My diet is quite good .My one concern is that I thought orange juice would help with absorption of iron but I have stopped taking it as I am afraid it’s acidity would aggravate stomach inflammation. Any thoughts or suggestions as I want to prepare for my 40 th marathon anniversary next year

  24. James Kenny

    I am a 63 year old male runner.I have ran 34 marathons dating back to 1982.In 1999 my iron levels dropped substantially.They were low for 6 months at least until I finally got blood tests.I got a blood transfusion which sorted my problem for the next 22 years. Back in 1999 I had 2 colonoscopies and 2 endoscopies , all were clear.Last October 2020 I did a virtual marathon, it went fine.I took 2 weeks off training and then resumed running for the next 6 weeks, very easy running.After Christmas I found it difficult to run.I got my blood tested in early February 2021.My haemoglobin had fallen to 8.1 and ferriten had fallen to 2.I got 2 iron transfusions.I had a colonoscopy which was clear. My endoscopy showed some inflammation in my stomach, possible cause of drop in my iron levels? I am on pentoflux tablets for a few weeks. My haemoglobin has risen after 1st iron transfusion to 11.I will be retesting my blood in 10 days which will be over 3 weeks after 2 Nd transfusion. I am still not sure if my running was a factor in my drop in iron levels.What I should do for the future? I will have a CT stomach scan later on .

  25. Megan Franz

    Thanks so much for this article. Such a nice overview. I am a 24yo female who has struggled with ‘hypoferritinemia’ since I was 16. In high school, I remember starting a run with teammates and having to stop a mile in to walk back to the track because my legs hurt so bad I simply couldn’t keep going. My ferritin was at 7 but my hemaglobin/hematocrit were within normal ranges, or just below normal ranges. Since then I have received iron sucrose infusions of varying dosages anywhere from 1-2 times a year which has been the only form of treatment that helped treat the symptoms. (Usually just given as-needed, or when I started to feel symptomatic which is typically when my ferritin drops to ~25 or lower). I was a competitive middle distance runner in high school and at the D1 level for college. These days I am training for my first marathon, and I hope to start getting into trail running. Throughout college I never questioned why I wasn’t retaining iron or sought further medical treatment other than the infusions. I’ve been on supplements (hemadyn pro, ferrous sulfate, proferrin) since I first found out about this at 16, I eat plenty of red meat and high-iron foods, I never struggled with eating disorders or body image issues. During my college athlete days, my doctor at the time said that ‘some women just don’t absorb iron’ and ‘things will re-equilibrate after you’re done with collegiate/elite running.’ But that really hasn’t been the case. In the last year I have been meeting with a dietician who confirmed the issue is not my iron intake. I have had a colonoscopy to confirm I am not losing iron there. I met with a hematologist who thinks I could have a rare internal bleeding condition? But due to difficulties getting lab work done this has not been confirmed. I have not been screened for any GI pathogens, but am wondering how significant an impact this could have on iron absorption? At this point, I’m curious if the only option for now is to rely on these semi-regular iron infusions for treatment? I feel very fortunate to have had a doctor who understood iron deficiency in endurance athletes and was more than happy to prescribe infusion treatments for me as-needed. However, it is very frustrating to not understand why I’m not retaining iron, or why I’m not absorbing what I consume via supplements and diet. Are there any remaining avenues I could explore? Can more info be obtained from a bone marrow biopsy other than just confirming iron deficiency?

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