Why iron-deficiency estimates for female athletes range from 15% to 57%

By Sarah Lee · 2026-07-24

If you've spent any time reading about iron and female athletes, you've seen the range. Somewhere between 15% and 57% of us are iron deficient. I kept running into it too, in blog posts and Instagram captions and the occasional coach's newsletter. So I went looking for the study behind it.

There isn't one.

That span isn't a finding. It's two different numbers, from two different groups of women, welded into one alarming-sounding range. Here's how it's built.

Where each end comes from

The low end you'll see, around 15 to 35%, gets pinned on a narrative review of iron in athletes: a summary that looked across various female athlete cohorts and reported deficiency somewhere in that band.¹ The high end, 57%, comes from a single study of 28 players called up to a national soccer team.² Twenty-eight players, on one team, in one country.

So the "15 to 57%" is a floor borrowed from a broad review and a ceiling borrowed from one small squad, two different kinds of study looking at two different groups of women. That alone should make you pause. But the deeper issue sits underneath both numbers.

The number that quadruples while nothing changes

Here's the part that made it click for me.

In a nationally representative US sample of 3,490 girls and young women aged 12 to 21, researchers measured iron deficiency three ways in the exact same blood.³ At a ferritin cutoff of under 15 micrograms per liter, 17.0% were iron deficient. At under 25, it was 38.6%. At under 50, it was 77.5%.

Same girls, same blood. The prevalence went from roughly one in six to more than three in four, and nobody's iron changed. The only thing that moved was the line the researchers drew.

That sample was the general population, not athletes, so it isn't a stand-in for a team. I'm leaning on it because it shows the effect more cleanly than any athlete study I've found: the cutoff is doing the talking.

Why there's no one right line

You might be wondering which of those cutoffs is the correct one. The honest answer is that there isn't a single agreed line. The study reported iron deficiency at all three, and that spread, from under 15 to under 50, is exactly the problem. The same blood is "deficient" or "fine" depending on which line you pick.

So when two sources hand you very different iron-deficiency numbers, they can both be right, and simply be drawing the line in different places.

How to read the next iron statistic you see

Two questions tell you almost everything: which women, and which cutoff. A number without both is a number you can't really use, whether it's on a supplement label, inside an app, or in something I write. It's why, when I give you a figure I'm standing behind, it carries the group it came from and the threshold behind it, read from the full paper rather than the abstract, which is exactly where those details go missing.

None of this means iron doesn't matter for female athletes. It matters a great deal, and in places the research is genuinely thin. It just means the tidy "15 to 57%" you keep seeing is far tidier than the science underneath it.

Sources

Sim M, Garvican-Lewis LA, Cox GR, et al. Iron considerations for the athlete: a narrative review. European Journal of Applied Physiology 2019;119(7):1463-1478. Narrative review across female and male athlete cohorts; source of the widely-cited 15-35% figure. DOI: 10.1007/s00421-019-04157-y
Landahl G, Adolfsson P, Börjesson M, et al. Iron deficiency and anemia: a common problem in female elite soccer players. International Journal of Sport Nutrition and Exercise Metabolism 2005;15(6):689-694. Cross-sectional; n=28 national-team players; source of the widely-cited 57% figure. DOI: 10.1123/ijsnem.15.6.689
Weyand AC, Chaitoff A, Freed GL, et al. Prevalence of Iron Deficiency and Iron-Deficiency Anemia in US Females Aged 12-21 Years, 2003-2020. JAMA 2023;329(24):2191-2193. Cross-sectional, NHANES; n=3,490; US females aged 12-21 (general population); measured by serum ferritin at three cutoffs. DOI: 10.1001/jama.2023.8020