The single most common deficiency in menstruating women — and a frequent hidden cause of fatigue, brain fog and low mood.
Iron makes haemoglobin, the protein in red blood cells that carries oxygen around your body. When iron runs low, every cell gets less oxygen — which is why deficiency shows up as deep fatigue, breathlessness, brain fog, mood changes and pale skin. For women, iron also matters hormonally: low iron can disrupt ovulation and is linked to irregular periods and reduced fertility.
Yes — when you're deficient, and that's common. Women of reproductive age are at the highest risk because of monthly blood loss, and iron deficiency without full-blown anaemia is roughly twice as common as anaemia itself, yet it's often missed. Correcting it reliably restores energy, concentration and mood. The crucial honest point: iron only helps if you're low — supplementing when you're not can cause harm, so this is one to confirm with a blood test, not guess at.
Persistent tiredness, breathlessness on stairs, a racing heart, brittle nails, hair shedding, brain fog, low mood, cravings for ice, and heavier-than-average periods. Vegetarians, vegans, endurance athletes and anyone with heavy bleeding are higher risk.
There are two kinds of dietary iron, and the difference matters enormously for women. Heme iron — from animal foods — is far better absorbed (around 15–35%): the richest sources are red meat (beef, lamb), liver and organ meats, followed by shellfish (clams, mussels, oysters), sardines, turkey and chicken. Non-heme iron — from plants — is absorbed much less efficiently (2–20%): lentils, beans, chickpeas, tofu, pumpkin seeds, spinach, fortified cereals and dark chocolate are good sources, but you absorb far less of it. This is the key reason vegetarians and vegans are at notably higher risk of deficiency and need to be more deliberate — pairing plant iron with vitamin C (peppers, citrus, tomatoes) significantly boosts absorption, while tea, coffee and calcium with the meal block it. For menstruating women losing iron monthly, this absorption gap is exactly why diet alone sometimes isn't enough.
The daily requirement for women 19–50 is about 18 mg (27 mg in pregnancy). But the right move is a ferritin blood test before supplementing — if you're low, a typical dose is 18–65 mg of elemental iron; if you're not, you shouldn't be taking it at all. Lower doses, or every-other-day dosing, are often absorbed better and are gentler on the gut.
Take iron with a source of vitamin C (a glass of orange juice, or with fruit) to boost absorption, and keep it away from calcium, dairy, tea and coffee, which block it. Full correction of stores takes 3–6 months, so retest rather than stopping the moment you feel better.
The body can't easily excrete excess iron, so over-supplementing is genuinely risky — it can damage organs over time. Postmenopausal women and anyone not menstruating should be especially careful and test before taking any. Keep iron supplements away from children, for whom overdose is dangerous.
Vitamin C is the key partner. If you're pregnant or trying to conceive, iron is usually best taken as part of a prenatal under your midwife's or doctor's guidance.
Don't take iron at the same time as a calcium supplement, dairy, tea, coffee, or certain medications (some thyroid and antibiotic medicines) — space them apart. And don't supplement at all without confirming you need it.
Postmenopausal and non-menstruating women (overload risk), and anyone with haemochromatosis or another iron-storage condition, should not supplement without medical advice. In pregnancy, follow your provider's dosing.
Ferrous bisglycinate (a chelated form) is the gentlest on the stomach and well absorbed, with far less constipation than ferrous sulfate. Choose a clearly dosed, third-party-tested product, and pick the dose to match your test results.
Iron is the most common and most overlooked deficiency in menstruating women, and fixing a real shortfall transforms energy, focus and mood. Test your ferritin first, choose a gentle bisglycinate form with vitamin C, keep it away from calcium and tea — and never supplement iron 'just in case'.
NIH Office of Dietary Supplements — Iron; American Medical Association — iron deficiency guidance; NHS — Iron; reviews of iron bisglycinate tolerability.
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Based on guidance from the NHS, NICE, Cleveland Clinic and peer-reviewed research.
General information, not a substitute for personal medical advice — always consult your doctor or a qualified health professional before making health decisions. If you are pregnant, breastfeeding, trying to conceive, under 18, or taking medication, speak to your doctor before starting any supplement.