Anemia in women who train: how to spot it and what to do

Fatigue that survives eight hours of sleep, breathlessness during a warm-up that used to feel easy, and heavy legs by the third set – most people blame a bad week or too much training. In women of reproductive age, the reason behind it is very often low iron, with or without anemia. Telling those two apart is a blood test, not a guess.

Why training women are a higher-risk group

Several things stack up at once:

• Menstrual losses. An average cycle costs 30–40 ml of blood, roughly 15–20 mg of iron per month. Heavy bleeding (over 80 ml) doubles that bill.
• Foot strike. Running longer than 60 minutes mechanically destroys a small share of red blood cells. Trivial per session, meaningful over months.
• Hepcidin. This hormone rises for 3–6 hours after a hard session and iron absorption drops while it is up. An iron-rich meal in the morning beats one right after an evening workout.
• Low intake. A 1400–1600 kcal diet rarely delivers more than 10–12 mg of iron a day. You absorb 15–35% of iron from meat but only 2–10% from plant sources.

Signs people write off as tiredness

• Resting heart rate 5–10 beats higher than usual with no other change in your routine
• Getting winded on stairs or during a 5-minute warm-up
• Endurance drops before strength – the 5 km run goes first, the squat holds up longer
• Cold hands and feet, hair shedding, brittle nails
• Craving ice, ice water or chalk – a sign that is almost specific to iron deficiency
• Slower recovery between sets, struggling to hold the same load across 4 sets

Blood work: what to order and how to read it

Ask for a full blood count (hemoglobin, MCV), ferritin, transferrin saturation and CRP. A blood count alone is not enough, because iron stores can sit empty for months before hemoglobin falls.

• Hemoglobin below 120 g/L (12 g/dL) means anemia in women. Below 110 g/L is a serious drop.
• Ferritin below 15 ng/ml means empty stores. Below 30 ng/ml, training women usually already feel it even with a normal blood count.
• Transferrin saturation below 20% confirms the deficiency.
• CRP is the sanity check: inflammation or a hard session falsely raises ferritin, so the result looks better than reality.

Practically: draw blood in the morning, fasted, and at least 48 hours after a hard session or a long run. Otherwise your ferritin can read 20–30 units higher than it truly is.

Normal hemoglobin does not mean normal iron. Testing only the blood count misses the most common stage – iron deficiency without anemia.

Food: how much and from where

The general target for menstruating women is 18 mg of iron per day. For regular endurance training, multiply by 1.3–1.7, so 23–30 mg. If you eat no meat, multiply by 1.8 – around 32 mg a day, which is hard to hit without planning.

Rough guide per 100 g: beef 2.6 mg, liver 6–9 mg, mussels around 6 mg, sardines 2.9 mg, dark chicken meat 1.3 mg, cooked lentils 3.3 mg, chickpeas 2.9 mg, tofu 2.7 mg, pumpkin seeds 8 mg (a 30 g handful gives 2.4 mg).

• Pair plant sources with 75–100 mg of vitamin C in the same meal – one bell pepper has about 120 mg, a kiwi about 70 mg. It can double absorption.
• Coffee and black tea cut absorption by 50–60%. Move them 60 minutes away from iron-rich meals.
• More than 300 mg of calcium (a glass of milk, a large yogurt) in the same meal also interferes – separate them.
• Cooking in cast iron realistically adds 1–2 mg per meal, especially with acidic dishes.

Supplements – only after a test

Iron is not something you take on a hunch. Once a test confirms the deficiency, the standard approach is 60–100 mg of elemental iron every other day, in the morning on an empty stomach, with vitamin C. Every other day is deliberate, not lazy – daily dosing raises hepcidin and the next dose absorbs worse. Retest in 8–12 weeks; refilling stores takes 3–6 months. Expect dark stools and possible constipation. Do not extend treatment without a follow-up test – too much iron is as much a problem as too little.

Training while you fix the numbers

• Cut weekly volume by 20–30% for 2–3 weeks and add one rest day.
• Keep lifting: 2–3 sessions per week, 3–4 sets of 6–10 reps, 2–3 minutes rest, load at RPE 7 (leave 3 reps in reserve).
• Drop intervals and HIIT to once a week, and cut them entirely if hemoglobin is under 110 g/L.
• Keep cardio easy: 30–45 minutes at a pace where you can talk in full sentences.
• Expect the first real change in training to show up in 4–8 weeks, not seven days.

When to see a doctor

• Same day: chest pain, fainting, breathlessness while walking normally, or a resting heart rate over 100.
• Hemoglobin below 100 g/L on your results.
• Bleeding longer than 7 days, soaking a pad every 1–2 hours, or clots larger than 2 cm – that is a gynecologist, not a supplement.
• Black or tarry stools, blood in stool, abdominal pain – never self-treat this.
• Ferritin that has not moved after 3 months of proper treatment.
• Iron deficiency in a postmenopausal woman – the source of blood loss gets investigated, not assumed to be diet.

The short version

• Test ferritin, not just the blood count – and do it 48 hours after a hard session.
• Ferritin under 30 ng/ml with symptoms is worth acting on, even with normal hemoglobin.
• Aim for 23–30 mg of iron a day from food, with vitamin C and no coffee within an hour.
• Supplement only after testing, typically 60–100 mg every other day, retest in 8–12 weeks.
• While recovering: lift 2–3 times a week for 3–4 sets, cut volume 20–30%, park the HIIT.