Correcting iron deficiencies in endurance athletes.

By Jeff Rocco, MD


Iron is a critical mineral for performance in endurance athletes. The abridged story of iron is that it is necessary to create hemoglobin, which is the protein used by red blood cells to deliver oxygen and remove carbon dioxide from an athlete’s exercising muscles.  

More hemoglobin = More oxygen delivery + CO2 disposal

Previously we have presented and discussed some of the basics of iron metabolism.  For a review of that material please see the Iron and Endurance Athletes article.

What follows is a discussion of symptoms, causes, diagnosis, and treatment of iron deficiency anemia in endurance athletes, including how MultiV can be part of an iron repletion and maintenance regimen.

As it turns out, many endurance athletes are iron deficient. In fact, about 90% of the patients I have evaluated for iron deficiency tested positive, and it seems that the higher performing athletes are more severely affected.

Recently, I have also personally experienced the diagnosis of iron deficiency – and the subsequent benefits that occurred when the deficiency was corrected.


Symptoms of iron deficiency may be mistaken for over-training syndrome (OTS).  Previously, we have discussed OTS here: How To Stop Cortisol and Overtraining Syndrome From Wrecking Your Season. The athlete may simply feel generalized fatigue and find no improvement (or decreasing) performance despite vigilance and attention to recovery, nutrition, and training plans. Assuming that bleeding such as from a colonic polyp or heavy menstruation have been ruled out, the mechanism for anemia in endurance athletes is not entirely clear.


Foot strike hemolysis is occasionally cited as a possible culprit. It can occur in runners when repeated foot falls cause mechanical breakdown of red blood cells; however, recent studies have shown that this effect may be clinically insignificant., Foot strike hemolysis also fails to explain why cyclists exhibit iron deficiency anemia with alarming frequency.

More recently, oxidative stress and inflammation caused by high volume of exercise and high-intensity exercise have been proposed as the cause of alterations in the red blood cell membrane, subsequently resulting in hemolysis., That suggests the cause of athletic induced anemia may just be the increased levels of oxidative metabolism seen in endurance athletes compared to sedentary individuals.


Iron deficiency anemia is diagnosed with blood tests. The tests necessary to make the diagnosis include a complete blood count (CBC) with differential, and an iron panel which includes: serum iron, total iron binding capacity (TIBC), iron saturation, and ferritin.

The range of normal is quite wide, and many times patients – and especially athletes – may be told their levels are normal, when in fact they are low. Here’s why: Normal values can vary between laboratories, and normal is a range of values clustered around a mean value for that particular lab. In other words there are a lot of results that are considered “normal” simply because they occur commonly.  Many of the population tested have some sort of illness that may cause a low hematocrit, so while the results for these patients might be considered normal for those specific circumstances, they are far from normal for a high-performance athlete.  

For example, consider hematocrit (the volume percentage of blood that is made up of red blood cells). The normal range for hematocrit is 40-49% for men and 35-46% for women. Doctors are used to treating patients with medical conditions that cause their patients to have hematocrits in the anemic range. So when a doctor sees a 45-year-old age group athlete who lives at 5000’ above sea level with a hematocrit of 39%, that athlete might be told their hematocrit – and therefore their iron level – is within the normal range. However, if the doctor digs a bit deeper and orders an iron panel, more information is uncovered. Let’s consider that same athlete with the following lab results:






13.3-16.7 g/dL



40.0-49.6 %



65-175 mcg/dL






250-450 mcg/dL



5-244 ng/ml

A doctor might look at those results and conclude that this hematocrit and iron panel are both normal. But they aren’t. Not for an otherwise healthy athlete who lives at 5000’ above sea level.

Living and training at altitude should stimulate red blood cell production to the high end of the normal range, but the values for hemoglobin and hematocrit are at the low end of the range. An Iron level of 68 is much closer to 65 than it is 175.

Additionally, if this athlete had been female, this same lab might have reported the low end of the range as 37mcg. Iron levels shouldn’t be lower in women, but they commonly are due to menstruation and child bearing; a woman’s iron stores can drop by as much as 25% with every child she bears.

In light of this context, the low % saturation and the normal TIBC in the example above tell us that this athlete’s body has the capacity to deal more iron.


Common sense might suggest this athlete must just need a better diet and some iron supplements. Come to find out that this athlete has already been on supplements for the past 3 years and is still low on iron.

The point here is that it takes years to improve total body iron stores with oral supplements, and may not even be possible at all.  The body has a difficult time absorbing enough iron to keep up with the depletion caused by high volumes of intense exercise, so intravenous (IV) therapy is ofetn required to make any real, meaningful change. After IV iron treatment, this particular athlete’s hematocrit increased from 39.7% to 45% in just 6 weeks. That’s a 13.3% improvement, which translates into 13.3% more oxygen carrying capacity.

To treat iron deficiency anemia I generally recommend a total of 5 IV infusions of iron with one week between each infusion. The week between infusions gives the body time to process the iron and bind it to proteins.  Too much iron, given too quickly, can be toxic and cause liver damage. The infusions generally are given slowly over about half an hour. During the 5 week period of the infusions, it is important for athletes to consume extra protein, up to 1g per pound of body weight. The body needs both iron and protein to manufacture the red blood cells.  Athletes can and should continue to train as usual during the infusion period. Many patients (athletes included) start to feel like they have more energy after only one or two treatments.


Once IV therapy has been completed, additional IV therapy should not be needed for years. At that point iron levels can be maintained with an oral supplement. First Endurance MultiV has a good dose of iron (18mg of elemental iron, chelated) for maintenance purposes. In my own personal experience, this approach to iron deficiency has helped me to not only to perform better, but to feel better too.

December 29, 2022 — First Endurance
Tags: research


Luke said:

I am sending Dr. Rocco’s response to your question Tony, with his permission.
Disclaimer: First Endurance sells dietary supplements, which is a food, not a pharmaceutical (drug). Intravenous iron is not a supplement, but is regulated as a drug, and therefore, we are complying with dietary supplement regulations about not making or implying drug claims for First Endurance products. Any further information on intravenous iron should be via consultation with a medical doctor about your personal considerations, especially in regards to wha type of infusion to use. We thank Dr. Rocco for his helpful insights and education and are posting his response in order to satisfy readers’ requests to the extent that we are allowed.
Luke R. Bucci, PhD CCN CNS Chief Scientific Officer

Dr. Rocco’s Response to iron question:
Deciding to give an iron infusion can be a complex decision. And while this is not a forum to provide medical treatment and advice, I might be able to shed some light on the question of iron infusion. While your iron may be low normal and the Ferritin is normal, it would also be good to know the iron saturation, the hematocrit, the hemoglobin, and the MCV. Testosterone levels may also play a role here. Combine this data with your personal health history and any medications you might be taking. Also your age and where you live may affect what might be a normal iron level and hematocrit. The decision to infuse iron simply isn’t a matter of having a low iron level. Ultimately, the physician needs to consider the patient as a whole in the appropriate context. I personally would not rule out an infusion with a ferritin in the low “normal” range. However, that doesn’t necessarily mean I would always choose to infuse iron.
As to which iron infusion to use there are currently 5 or 6 different drugs available.
A final consideration lies with anti doping. While a diagnosis of iron deficiency anemia and infusion of iv iron would be considered medically necessary and allowed, any iv infusion with greater than 100ml would violate WADA regulations.
Hope this helps
Jeffrey Rocco, M.D.

Luke said:

Thanks for this question! Ah, the ole heme iron absorption issue again. Actually, technically speaking, hemoglobin has iron in it, not the other way around. And Ferrochel chelate has human clinical studies showing significantly better tolerability than other iron salts or chelates, especially in pregnant women and children. Another func heme fact – the first precursor to make heme is glycine itself, which is then congealed in at least 9 biosynthesis steps to form heme protoporphyrin, so heme is actually a much larger molecular version of a glycine chelate embedded in heme protein (globin). Although there are a lot of good reasons to use Ferrochel (ferrous bisglycinate) instead of heme iron, there is one reason that is all-important: stability. Ferrochel is extremely stable and keeps iron in its unoxidized ferrous state. Heme, on the other hand, degrades into numerous fragments on exposure to oxygen (air), as is the situation with dietary supplements. That’s why Heme iron supplements are not made – they’re not stable. Less stability = less safety when iron is concerned. Also, Ferrochel is the most- and best-studied iron chelate in humans, and has been in use worldwide for over 50 years with superior safety.
Luke R. Bucci, PhD CCN CNS Chief Scientific Officer

Luke said:

Warren, I have used Ferrochel (ferrous (iron) bisglycinate) as an iron only supplement during my clinical practice days and was very happy with the results. I also recommend that adding iron supplements should have some iron testing from a qualified health care practitioner beforehand to make sure there is a need.
Luke R. Bucci, PhD CCN CNS Chief Scientific Officer

swim said:

heme -iron. Red meat &animal proteins/animal organs. Iron that has hemoglobin in it! And avoid the gastro of elemental chelated iron.

tony giguere said:

with your " normal" levels. how do you convince your doctor to give you an iron infusion? i have very similar iron levels but only when my ferritin is below normal will they consider the infusion. what type of iron infusion do you get? thanks for the info. tony

Warren C Mullisen said:

is there a specific iron only supplement to recommend?

Warren C Mullisen said:

is there a specific iron only supplement you recommend?

Leave a comment

Please note: comments must be approved before they are published.

Join The Conversation

Did you find this post interesting and valuable or was it a waste of your time? Do you have a topic you’d like us to cover or a question you’d like answered? If so, leave a comment below and we'll get back to you right away.

    1 out of ...