Iron Deficiency in Athletes: A Complete Guide to Food, Labs, and Supplements
- Jul 2
- 5 min read
You're tired. Your hair is shedding. Your performance is declining. Or you discover that your ferritin is low. So you start taking an iron supplement.
But a few months later, nothing has changed. Or, maybe you even start to feel worse. Sound familiar?
Iron is a lot more complicated than a single lab value. Taking a supplement just because you're tired is a common move, but without knowing the full picture, you might be wasting money or even creating more problems.
In episode 140 of The Eat for Endurance Podcast, I'm joined by fellow Sports Dietitian Callie Roseland, MS, RDN, CSSD to break down everything you need to know about iron and ferritin as an active person.
Callie and I discuss:
The difference between iron deficiency and anemia
Who's most at risk
Common signs and symptoms of low iron and ferritin
Which blood tests to order
Why "normal" lab values aren't always optimal
What low ferritin but "normal" iron actually means
How gut health as well as different foods influence iron absorption
How much iron you need from food, plus meal/snack ideas
When supplementation makes sense
Iron supplement timing and practical strategies
By the end of this episode, you'll know exactly which labs to ask for, why your ferritin might be low (and it's not always just about iron), how to optimize your iron through a food-first approach, and when supplementation may be appropriate for YOU.
Iron Deficiency in Athletes: It's More Complex Than You Think
One of the biggest takeaways from this conversation is that iron deficiency in athletes is rarely as simple as just "eat more iron."
Iron plays an essential role in oxygen transport, energy production, aerobic performance, immune function, and cognitive health, making it especially important for endurance athletes. But here's the thing: your body also has to absorb, transport, and properly utilize that iron. That's where it gets complicated.
Iron status is influenced by so much more than dietary intake of iron alone. Gut health, inflammation, underfueling, menstrual losses, poor absorption, and intake of other micronutrients (like Vitamin A, B12, copper, and magnesium) all play a role. That's exactly why taking a supplement without understanding what's actually driving your low ferritin may not work.
Who's Most at Risk?
Certain populations are particularly vulnerable to iron deficiency, including:
Female endurance athletes: Monthly menstruation plus losses from running impact and training stress make it harder to meet daily needs.
Vegetarians and vegans: Non-heme iron (from plants) is absorbed at much lower rates than heme iron (from animal sources), requiring more strategic eating and higher overall iron intake.
Athletes with chronic underfueling or gut issues: Low energy availability suppresses iron absorption, while chronic GI issues like celiac, SIBO, or dysbiosis impair absorption even when iron intake is adequate.
Distance runners and high-volume endurance athletes: Increased red blood cell turnover, training-induced GI stress, and the sheer demands of high mileage all increase iron needs.
Signs Your Iron Might Be Low
One symptom alone doesn't necessarily point to iron deficiency or anemia, but common signs include:
Persistent fatigue that doesn't improve with rest or caffeine
Declining performance
Poor recovery
Feeling unusually cold
Pale skin
Hair thinning or excessive shedding
Spoon-shaped nails
It's also important to keep in mind that fatigue is a nonspecific symptom. It could be iron, or it could be a dozen other things. That's exactly why getting labwork done is so important.
What Does Low Ferritin but Normal Iron Mean?
This is one of the biggest causes of confusion for athletes, and one of the main reasons this episode exists.
Many athletes are told their iron is "normal," yet they're exhausted, struggling through workouts, or experiencing declining performance. Their ferritin is technically within the lab's reference range, but they still feel awful.
As Callie explained in the episode, “You can have normal or even high iron and low ferritin... and that is not a good thing."
Ferritin reflects your body's iron stores, while serum iron measures what's circulating in your bloodstream. Looking at one without the other doesn't tell the whole story.
A more comprehensive iron panel includes these two biomarkers, as well as:
Total iron binding capacity: Measures how well your body's iron-transport protein (i.e. transferrin) can carry iron
Transferrin saturation: Percentage of iron that transferrin is actively carrying
Complete blood count, including hemoglobin, red blood cells, and hematocrit
C-reactive protein: An inflammation marker
Another important point: "normal" doesn't always mean optimal for athletes. Many labs use broad reference ranges, but performance-minded practitioners often aim for higher ferritin levels depending on training demands and symptoms.
"Test, Don't Guess"
Callie's mantra throughout the episode is simple but powerful: "Test, don't guess."
Taking an iron supplement because you're tired or assume you're supposed to can sometimes do more harm than good. The goal isn't just to take a pill. It's to understand why your iron status is low in the first place, get to the root of the problem, and then find the right solution (which might be food, supplementation, addressing gut health, or fixing underfueling).
For the full breakdown on testing protocols, supplementation strategies, and how to optimize your iron through food, listen to the full episode!
Ready to Dig Deeper?
If you're constantly fatigued, struggling with low ferritin, or confused by your lab work, working with a sports dietitian can be really valuable. We can look at your nutrition, training, recovery, gut health, and lab work to identify what's actually driving your symptoms.
Here’s what one client had to say about working with me:
"I decided to work 1:1 with Claire about 6 months ago and it has been the best investment I have ever made. My skin is 100% clear. My hair is no longer falling out. My cycle length is just about perfect and I have no cramps. I also feel so much stronger during my workouts. But I have to say, the best part of all is how much calmer I feel. I used to always feel so wound up and was constantly yelling at my kids. I am not just a better athlete but also a better wife and mother because I am nourished and I have Claire’s knowledge and expertise to thank."
-Anna L.
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Grab my Eat for Endurance Mini Guide Bundle (a collection of 6 mini guides, worksheets, and a bonus supplement resource)
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Disclaimer: All information provided is for educational and entertainment purposes only and is in no way meant to replace individual medical and nutrition recommendations.
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