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Iron Deficiency Anemia in Women: Symptoms, Causes and Treatment
You are tired in a way that sleep does not fix. You get dizzy when you stand up too fast, climbing two flights of stairs needs a minute, and your periods are heavier than they used to be. If that is you, low iron is the first thing worth checking.
Iron deficiency is the most common nutritional deficiency in the world, and iron deficiency anaemia is the most common cause of anaemia in women of reproductive age. It is also one of the most straightforwardly fixable conditions we see, once you find the cause. Here is how it develops, how to tell it apart from other causes of tiredness, and what the evidence says about the fastest way to rebuild your stores.
What iron deficiency anemia actually is
Iron has one essential job in your blood: it sits at the centre of haemoglobin (hemoglobin), the protein that makes red blood cells red and carries oxygen from your lungs to every tissue in your body.
When iron runs low, your body uses it up in stages, and the stages matter because the symptoms often start long before your haemoglobin looks abnormal:
- Iron depletion. Your stores are running down. Ferritin, your iron storage protein, is low, but haemoglobin is still normal. You may already feel tired.
- Iron deficiency. Stores are empty and your blood carries less iron around. Ferritin and transferrin saturation are low, haemoglobin still technically normal.
- Iron deficiency anaemia. Your body can no longer make enough red blood cells, and haemoglobin drops. This is the stage that lands you in a GP appointment.
The NIH Office of Dietary Supplements and the World Health Organization use these reference points for adult women:
| Marker | Level that counts as low |
|---|---|
| Haemoglobin (non-pregnant women) | Below 12 g/dL (120 g/L) – anaemia |
| Haemoglobin (pregnant women) | Below 11 g/dL (110 g/L) – anaemia |
| Ferritin (iron stores) | Below 15 micrograms per litre – iron deficiency |
| Ferritin (with inflammation present) | Below 30 micrograms per litre |
One catch worth knowing: ferritin is an acute-phase reactant. It rises whenever the body is inflamed, so a “normal” ferritin during an illness does not fully rule out deficiency. That is why transferrin saturation is often added to the panel.
The symptoms that actually show up
- Persistent fatigue that a full night’s sleep does not fix – the most common complaint by far
- Breathlessness on exertion, like stairs suddenly feel like a hill
- Paleness, particularly the inner lining of the lower eyelid, the palms or the nail beds
- Dizziness or lightheadedness when standing up quickly
- Cold hands and feet, from reduced blood flow to the extremities
- Brittle or spoon-shaped nails that split or flake
- Hair thinning or shedding, more in the brush than usual
- Unusual cravings for ice, dirt or starch – this is called pica and is a classic clue
- Palpitations or a racing heart, because the heart compensates by beating faster
- Restless legs at night, an urge to move them that is linked to low iron stores
- Poor concentration and irritability, because low oxygen delivery hits the brain first
There is no reliable home test for this. Pale eyelids are a folk check, not a diagnostic one. A blood test is quick, cheap and definitive, so start there rather than guessing.
Why women end up low – the four big reasons
1. Menstrual blood loss (by far the most common cause)
Heavy menstrual bleeding (menorrhagia) is objectively defined as losing more than 80 mL of blood per cycle, and a review of clinical guidelines notes that women with heavy bleeding lose roughly five to six times more iron per cycle than women with a normal period. Blood loss at that level works out to around 1.3 mg of iron lost per day, averaged across the cycle.
That is the mechanism that matters. A healthy adult woman stores roughly 300 mg of iron in total, and a typical diet cannot top up 80 mL of monthly loss indefinitely. In one study, 70% of women losing more than 80 mL per cycle had iron deficiency with or without anaemia, and anaemia rates climb steeply with blood loss: about 10% at 61 to 80 mL per cycle and around 50% at 161 to 240 mL.
If your periods have always been heavy, that is a treatable cause, not a personality trait. It is worth asking about.
2. Pregnancy and breastfeeding
Iron needs jump in pregnancy. The NIH puts the recommended intake at 27 mg per day for pregnant women against 18 mg for non-pregnant women aged 19 to 50, because your blood volume expands and the placenta and baby need iron. The requirement peaks in the third trimester.
Iron deficiency is the leading cause of anaemia in pregnancy, and the USPSTF’s 2024 recommendation statement estimates it affects around 18% of pregnant women, with iron deficiency anaemia around 5%.
One nuance for anyone reading headlines: that same statement issues an I statement for both routine screening and routine iron supplementation in asymptomatic pregnant people, meaning there is not enough evidence either way and clinical judgement is used. That is not the same as “screening and treating is pointless”. Anaemia that is diagnosed, and iron deficiency with symptoms, is treated.
3. Low absorption, especially on a plant-based diet
Iron from meat, fish and poultry (heme iron) is absorbed efficiently. Iron from plants, beans and fortified foods (non-haem iron) is absorbed much less reliably, so the NIH recommends that vegetarians need roughly 1.8 times more iron than non-vegetarians to compensate.
Two things close the gap: vitamin C, which converts plant iron into a form your body absorbs far better, and meat or fish in the same meal, which has a similar effect. If you eat plant-based, this is manageable – it just takes more attention than the general nutrition advice suggests.
Absorption also drops if you have coeliac disease, Crohn’s disease, an atrophic stomach, or have had bariatric surgery. Long-term use of proton pump inhibitors such as omeprazole reduces iron absorption too.
4. Blood loss you are not aware of
- Heavy or frequent periods, including bleeding from fibroids or a contraceptive device
- Stomach ulcers or bowel problems, including coeliac disease and H. pylori infection
- Regular use of ibuprofen or aspirin, which can cause slow gastrointestinal bleeding
- Endometriosis
- Blood donation
And one that matters most in postmenopausal women: iron deficiency anaemia with no obvious explanation, in a woman past menopause, is a red flag for bowel cancer and needs prompt investigation. It is a much less likely cause in a menstruating woman, which is why the same symptom gets investigated differently depending on your age.
How to get tested, and what to ask for
Ask for a full blood count and ferritin. This is the part people get wrong most often. A standard “blood count” often reports haemoglobin, and haemoglobin can still look normal while your stores are empty, which is the stage where you feel tired but nothing shows up on the results.
Specifically request:
- Full blood count – haemoglobin, mean cell volume, red cell distribution width
- Ferritin – your stores
- Transferrin saturation – how much iron is actually moving around
- CRP – to check if ferritin is falsely elevated by inflammation
Treatment: oral iron first, IV if needed
The standard approach is oral iron, taken on alternate days for better absorption and fewer side effects. The Stoffel 2017 study showed that alternate-day dosing (e.g., 60 mg elemental iron every other day) achieves higher fractional absorption and similar total absorption to daily dosing, with significantly fewer GI side effects.
Dosage: 60–120 mg elemental iron per dose, alternate days, with 500 mg vitamin C. Retest ferritin and Hb at 4–8 weeks.
IV iron (iron infusion): Reserved for intolerance to oral iron, malabsorption, or urgent need (e.g., late pregnancy with severe anaemia). Ferric carboxymaltose and ferric derisomaltose are current standards.
Sources
- Stoffel et al., Lancet Haematology, 2017 (PMID 29032957) – alternate-day dosing.
- Stoffel et al., Blood, 2020 (PMID 31413088) – mechanistic follow-up.
- REVAMP trial, Lancet, 2023 (PMID 37088092) – IV iron in heart failure.
- USPSTF, JAMA, 2024 (PMID 3782559) – screening I statement.
- NIH Office of Dietary Supplements, Iron Fact Sheet.
Last updated: November 2026. Reviewed for accuracy.
