Low iron in teenage athletes: the deficiency nobody looks for (and a blood test finds)

53.2% of athletes aged 11-18 have low iron stores, but only 4% are anaemic: deficiency arrives long before anaemia, and a normal blood count hides it. Since 2026 the American Academy of Pediatrics recommends a full blood count plus ferritin in every adolescent by age 14. What the evidence says, what actually raises the risk, and why the right move is a blood test — never a supplement taken alone.

There's a question almost nobody asks in youth women's sport: how is your athletes' iron? Not haemoglobin — that's what you look at once anaemia has already arrived. Stored iron. Ferritin. It's a number you get from an unremarkable blood test, one almost no girl has had, and in more than half of cases it comes back low.

In short

  • 53.2% of teenage athletes (11-18) have mild iron deficiency (ferritin ≤30 µg/L); only 4% have iron-deficiency anaemia (Nicotra et al., 2023).
  • Sport isn't the dominant factor: among adolescents, athletes and non-athletes don't differ significantly (Rowland et al., 1991).
  • Risk multiplies with heavy periods + a meat-restricted diet: odds 13.5 times higher (Söderman et al., 2025).
  • Since 2026 the AAP recommends a blood count and ferritin in every adolescent, by age 14 (AAP, 2026).
  • Test first, iron second. Never the other way round.

What is iron deficiency without anaemia, and why doesn't a full blood count show it?

Because haemoglobin is the last thing to give way. The body uses iron to carry oxygen, but it also keeps a reserve. As that reserve thins out, haemoglobin holds: the value stays normal, the routine test flags nothing, and meanwhile the stores are emptying. This is non-anaemic iron deficiency — and in numerical terms it's the rule, not the exception.

You can see it clearly in an Israeli study of 126 female athletes aged 11-18 playing basketball and football with at least five training sessions a week. Mild deficiency (ferritin ≤30 µg/L) affected 53.2%, moderate (≤20) 27.8%, severe (≤10) 4.8%. Iron-deficiency anaemia — the end stage — just 4% (Nicotra et al., 2023).

Translated: if you wait for anaemia to notice, you miss roughly 90% of the problem.

Is sport to blame? No — and that matters

The convenient story here would be: training drains your athletes' iron. The adolescent data doesn't support it, and it's worth being honest before someone else is.

One study directly compared, at the start of a season, swimmers (46.7%), runners (40%) and non-athletes (26.7%) below the 12 ng/ml threshold: the differences were not statistically significant, and mean ferritin levels didn't differ between groups (Rowland et al., 1991). And in Sweden, among 394 post-menarche students around age 16 — non-athletes — 73.6% had ferritin below 30 µg/L and 40% below 15 (Söderman et al., 2025).

The message isn't "so it doesn't matter". It's the opposite, and it's stronger: your athletes aren't at risk because they play sport, but because they're 13-17 and they menstruate. They're already in the highest-risk group in the paediatric population. Sport adds two things:

Which adolescent athletes are most at risk of iron deficiency?

Those with heavy menstrual bleeding and those restricting meat — and the two together multiply the risk rather than adding to it. The Swedish study has the merit of measuring the factors at the right age, and it yields two numbers a parent can use today. Among girls with heavy menstrual bleeding (52.8% of the sample) deficiency affected 51.9%, against 26.3% of the rest: odds 3 times higher. A meat-restricted diet carried odds 3.5 times higher. And the two together: 13.5 times (95% CI 6.4-28.7) (Söderman et al., 2025).

A heavy flow isn't a personality trait or something to "put up with": it's the first thing to name. And it's exactly the kind of information that never reaches the coach, where only 11% of athletes discuss their cycle with the person coaching them.

On the sporting side there are known mechanisms — exercise raises hepcidin, the hormone that reduces iron absorption, for roughly 3-6 hours after activity ends (Badenhorst et al., 2022) — but take them for what they are: documented in adult women, not adolescents. For this age group, that data simply doesn't exist.

"She's always tired": test first, iron second

It's the most natural temptation in the world, and it's the one to resist. Don't give iron supplements without a blood test.

This isn't box-ticking. Without documented deficiency, iron has no demonstrated benefit, frequently causes gastrointestinal side effects, and above all masks other causes of fatigue — which at 14 might be sleep, training load, school, or energy availability that's too low. The reverse holds too: lingering fatigue can sit alongside an injury that was never properly closed — an ankle that keeps giving way is the most common example in youth sport, and neither problem is solved by a supplement.

And even where deficiency exists, honesty requires saying the benefits are contested. A review of 12 studies across 283 participants found 6 studies showing improved performance and 6 showing none (Rubeor et al., 2018). The authors note that all six positive studies used a treatment threshold of ferritin ≤20 µg/L: below that line, supplementing appears to make more sense. The only trial run specifically on adolescent female athletes — 14 runners with ferritin under 20, double-blind — showed a significant improvement in treadmill endurance time, with no difference in VO2max (Rowland et al., 1988). Fourteen participants, in 1988: it's the best evidence at the right age we have, and it isn't much.

One temptation worth killing while we're here: iron is not a study aid. A systematic review of 50 studies in adolescents aged 10-19 concludes that supplementation does not improve memory and recall, and finds no evidence of an effect on intelligence, attention or concentration — with low quality of evidence throughout (Samson et al., 2022).

What the guidelines say (and this changed recently)

This is the solid part. In 2026 the American Academy of Pediatrics updated its clinical report on iron deficiency, replacing the 2010 version, and recommends universal laboratory screening — a complete blood count plus serum ferritin — in all adolescents, at least one year post-menarche and no later than age 14, setting ferritin ≤30 ng/mL as the deficiency threshold in adolescents and menstruating people (AAP, 2026).

In parallel, a group of haematologists and sports medicine experts independently proposes screening with haemoglobin and ferritin around ages 14-15 (roughly three years post-menarche), repeated every five years, using the same 30 µg/L threshold — which has a sensitivity of 92%, against 25% for the old 12 µg/L cut-off (Revel-Vilk et al., 2025). The two recommendations don't agree on timing, but they converge on what matters: test, and test with ferritin.

Two caveats. First: Revel-Vilk and colleagues offer an expert proposal, not a professional-body guideline. Second: national guidance varies, and many countries have no equivalent universal screening recommendation. The decision rests with a paediatrician or sports physician — but the question is now a legitimate one, with a literature behind it.

What the people around the athlete can do

Where BAB fits

BAB doesn't diagnose, doesn't measure ferritin and doesn't replace a doctor. It helps an athlete recognise her own signals privately — energy, mood, recovery, sleep — and see them over time: because "I'm tired" said once is an impression, while eight weeks of logged fatigue is information worth taking to a professional. Clubs get only aggregated, anonymous signals: never an individual's health data.

A blood test costs little and takes five minutes. What actually costs is never having asked for one.

Sources

This article is for information only and does not constitute medical advice, nor a diagnostic tool. Do not take iron supplements without a blood test and a doctor's guidance. If fatigue persists or menstrual bleeding is heavy, speak to a healthcare professional.

How many teenage athletes have low iron?

More than one in two. In a study of 126 female athletes aged 11-18 playing basketball and football, 53.2% had mild iron deficiency (ferritin ≤30 µg/L), 27.8% moderate (≤20) and 4.8% severe (≤10); outright iron-deficiency anaemia affected 4% (Nicotra et al., 2023). That's the whole point: deficiency is far more common than anaemia, and it arrives much earlier.

Does sport cause iron deficiency?

Not according to the adolescent data, and it's only fair to say so. A study directly comparing swimmers (46.7%), runners (40%) and non-athletes (26.7%) below the 12 ng/ml threshold found no statistically significant differences between groups (Rowland et al., 1991). And in a Swedish study of 394 non-athlete students around age 16, 73.6% had ferritin below 30 µg/L (Söderman et al., 2025). The dominant factors aren't training: they're menstruation and diet. Sport adds reasons — ferritin declines across a season in runners (Rowland et al., 1987) — and raises the stakes, because fatigue costs more when you train.

Can I give my daughter an iron supplement if she's always tired?

No — not before a blood test. This isn't a formality: without documented deficiency, iron has no demonstrated benefit, frequently causes gastrointestinal side effects, and above all risks masking other causes of fatigue. Even where deficiency exists, performance benefits are contested: a review of 12 studies found 6 showing improvement and 6 showing none (Rubeor et al., 2018). The right sequence is a full blood count plus ferritin, then a doctor decides. Never the reverse.

Does iron deficiency give recognisable symptoms?

Not reliably enough to count on. Non-anaemic deficiency is defined by a laboratory value — ferritin — precisely because the blood count stays normal: in the study of 126 athletes aged 11-18, mild deficiency affected 53.2% while iron-deficiency anaemia affected only 4% (Nicotra et al., 2023). In other words, most girls with low stores have perfectly normal routine tests. That is why the 2026 clinical report from the American Academy of Pediatrics recommends laboratory screening rather than symptom-led suspicion. Fatigue that doesn't lift with rest is still a good reason to ask for the test — not to infer the diagnosis.

Does a vegetarian or low-meat diet increase the risk?

Yes, and it has been measured in the right age band. In a study of 394 post-menarcheal students of around 16, a diet limiting meat was associated with 3.5 times higher odds of deficiency; heavy menstrual bleeding with 3 times higher odds; the two combined with 13.5 times (95% CI 6.4-28.7) (Söderman et al., 2025). This is not an argument against vegetarian diets: it is an argument for testing. A well-planned meat-free diet is not a problem in itself — it is one more reason to measure ferritin instead of assuming it.

When should the check happen?

Since 2026 the American Academy of Pediatrics clinical report recommends universal laboratory screening with a complete blood count and serum ferritin in all adolescents, at least one year post-menarche and no later than age 14, with ferritin ≤30 ng/mL as the threshold for deficiency (AAP, 2026). Independently, a group of haematologists and sports medicine experts proposes screening around ages 14-15, repeated every five years (Revel-Vilk et al., 2025). Guidance varies by country — the decision rests with your paediatrician or sports physician.