You eat well, so why is your iron still low?
You eat well. You eat red meat. Maybe you've even been told your bloodwork is "fine." But your easy runs feel hard, your legs feel heavy, and you're tired in a way sleep doesn't fix.
If that sounds familiar, you're not imagining it. Low iron is one of the most common issues in female athletes, and it's much more common in women than in men.
Here's the thing: eating well and absorbing well aren't the same, especially when you train a lot. Let's look at why.
Meet hepcidin, the iron gatekeeper
Hepcidin is the hormone that controls how much iron you absorb. Think of it as the gatekeeper between your gut and your bloodstream.
After a hard or long session, the inflammation from training tells your liver to make more hepcidin. It peaks a few hours after you finish and blocks iron from crossing from your gut into your blood. So the iron in your post-run meal isn't all getting in.
This is a normal, temporary response, not a sign that something is wrong. But if you train hard most days, those windows add up, and absorption over the week can fall short of what you need.
The other usual suspects
Hepcidin isn't the only thing working against you. Athletes also lose or miss iron through a few other routes, and they tend to add up:
Periods. Monthly blood loss is one of the biggest reasons women run lower than men, especially with heavy periods.
Sweat. Small amounts of iron are lost in sweat, which matters more in long or hot sessions.
Gut stress on long runs. Long or intense efforts can cause small amounts of blood loss from the gut.
Foot strike. Repeated impact can break down some red blood cells. It's real, but probably not the main driver for most runners.
Not eating enough overall. This is the one people miss. Under-fuelling and low iron often show up together, and there's emerging research that low carbohydrate intake may raise hepcidin after exercise. (More on under-fuelling in Is it normal to lose your period from running?)
So if your iron keeps coming back low, the question isn't only "how much iron am I eating?" It's also "am I eating enough, period?"
What low iron can feel like
In anyone:
Tired all the time
Short of breath with stairs or effort
Always cold
Headaches
Hair shedding or brittle nails
Restless legs at night
Craving ice (yes, really)
In runners:
Easy runs feel harder than they should
Heart rate higher than usual at your easy pace
Heavy legs
Recovery taking longer
Paces slipping even though training is consistent
This can happen even when your hemoglobin is "normal." Iron stores can run low well before anemia shows up on a blood test.
Why ferritin alone doesn't always show the full picture
Ferritin is the marker most people know. It reflects your iron stores, and it's a great place to start. But it has a catch: ferritin also rises with inflammation. A hard workout, a race or a cold can make it look better than it really is.
It's also just one snapshot. It doesn't show how much iron is actually circulating and available for your body to use.
That's why a fuller picture usually helps:
Ask for a full iron panel, which typically includes ferritin, hemoglobin and transferrin saturation (how much iron is circulating and ready to use)
Test after a rest or easy day, not right after a race or a big training week
Look at the trend over time, not just one number
What can help (and why not to guess)
Don't start iron on your own. It's tempting to grab a supplement, but more isn't better. Too much iron can cause stomach upset and, over time, build up in the body. Some people also have conditions that make extra iron a bad idea. The right plan depends on your numbers, so test first.
With proper testing, a plan for low iron in active women often looks at:
Eating enough overall, so your body isn't working from an energy deficit
Iron-rich foods, including heme iron (from meat, poultry and fish), which is absorbed more easily than iron from plants
Pairing and spacing: vitamin C–rich foods with plant-based iron, and coffee or tea away from iron-rich meals
Timing around training, since hepcidin rises a few hours after hard sessions
Supplementation when it's actually needed, with the dose, form and schedule matched to your bloodwork and rechecked over time
This is the kind of work I do as a naturopathic doctor with a background in health and exercise science. I look at your training, fuelling, cycle and bloodwork together, and help you build a care team, so you're not left guessing.
FAQ
Why is my iron low even though I eat well? Eating well and absorbing well aren't the same. In athletes, training raises a hormone called hepcidin that temporarily blocks iron absorption. Periods, sweat, gut stress and under-fuelling can add to the gap.
What is hepcidin? Hepcidin is the hormone that controls how much iron you absorb. It rises for a few hours after hard or long exercise and blocks iron from moving from your gut into your blood.
Can my iron be low if my hemoglobin is normal? Yes. Your iron stores can run low before hemoglobin drops, so you can have symptoms even when your hemoglobin looks normal.
Why doesn't ferritin always show the full picture? Ferritin also rises with inflammation, so testing after a race, a hard week or an illness can make it look higher than it really is. A full iron panel and the trend over time give a clearer picture.
Should I take an iron supplement if I'm a runner? Not without testing first. More iron isn't always better, and the right dose and timing depend on your bloodwork.
Formatting tip: mark this section up with FAQ schema so Google can show it in search results.
The bottom line
If your iron keeps coming back low despite eating well, it's not a willpower or diet failure. Training changes how your body handles iron. With the right testing and a plan that fits your training, it's very manageable.
If this sounds like you, you don't have to keep guessing. Book a strategy session with me to talk it through, or follow along on Instagram @drmadisonthorne for more on hormones, fuelling and cycles for active women.
This post is for general education and isn't a substitute for individual medical advice. Please see a qualified healthcare provider about your own health.
About the author Dr. Madison Thorne, ND, BHES, is a naturopathic doctor in Calgary, Alberta, with a degree in health and exercise science. She helps active women understand their hormones, fuel properly, and keep doing the sport they love. She's also a runner.