Written for Stock My Medicine and clinically reviewed by Hajra Dhanchora, MPharm (GPhC 2216990).
Iron deficiency is the most common nutritional shortfall in the UK, and the most under-recognised, because its headline symptom, tiredness, has a hundred other explanations. Around a quarter of women of childbearing age run low; so do many teenagers, pregnant women, endurance athletes and people on plant-based diets. Here's what low iron feels like, why it happens, how it's confirmed, and how the pharmacy supplements compare with the tablets a GP prescribes, because they're not the same thing and they're not for the same job.
Iron deficiency symptoms
Iron carries oxygen in the blood, so the symptoms are those of a body running on less: tiredness that sleep doesn't fix, breathlessness on stairs, a pounding or racing heart, pale skin and inner eyelids, headaches and finding it hard to concentrate. The less obvious ones, the "weird signs" that get searched: hair thinning or shedding, brittle or spoon-shaped nails, a sore or smooth tongue, cracks at the corners of the mouth, restless legs at night, feeling the cold, itchy skin, ringing in the ears, and craving ice or, oddly, things that aren't food. Iron deficiency goes through stages: stores (ferritin) drop first with no symptoms, then the iron available for making blood falls, and only then does the haemoglobin drop into anaemia. Symptoms often start before the anaemia does.
What causes iron deficiency?
Either you're losing iron, not absorbing it, or not getting enough. In women the commonest cause is heavy periods; our period pain guide covers what counts as heavy. Pregnancy needs a lot more iron than most diets provide. Beyond that: slow bleeding from the gut (ulcers, piles, regular ibuprofen or aspirin, and, in older adults, bowel conditions that must be ruled out), coeliac disease and other absorption problems, a vegetarian or vegan diet without careful planning, frequent blood donation, and endurance training. In men and post-menopausal women, iron deficiency is never put down to diet without checking the gut first, which is why a GP will ask questions rather than simply hand over tablets.
How it's diagnosed: the ferritin test
A simple blood test. The GP checks a full blood count for haemoglobin and red cell size, and ferritin, which measures your iron stores. Ferritin under about 30 micrograms per litre means the stores are depleted, even with normal haemoglobin, and symptoms can be real at that level. Ferritin rises with infection and inflammation, so a "normal" result during a cold can hide a deficiency; mention it if you were unwell on the day. Don't guess and don't start high-dose iron without the test: iron overload is harmful, the symptoms of low iron overlap with thyroid problems, B12 deficiency and more, and treating blind means the cause goes unfound.
How iron deficiency is treated
| Option | What it is | Best for |
|---|---|---|
| Prescription iron tablets | Ferrous sulfate or fumarate, around 65mg of iron per tablet, usually once a day or alternate days for up to six months | Confirmed anaemia. The dose needed to rebuild stores; it's why pharmacy supplements can't substitute for it. |
| Floradix Liquid Iron | Iron gluconate in a fruit and herb base with vitamin C and B vitamins, about 10mg per dose | Topping up borderline iron, maintenance after a course of tablets, people who can't tolerate tablets. Gentle on the stomach; the Floravital version is gluten- and yeast-free. |
| Spatone | Natural iron-rich spa water, 5mg per sachet, absorbed unusually well | Pregnancy, teenagers, athletes, anyone who gets constipated on tablets. Low dose, so it's a maintainer rather than a fix. |
| Gentle iron tablets | Iron bisglycinate, 14 to 20mg, from our iron supplements collection | Daily insurance on a plant-based diet or with heavy periods, with fewer stomach effects than ferrous sulfate. |
Prescription iron commonly causes constipation, black stools (harmless), nausea and stomach ache. Taking it alternate days, with food, or switching to a liquid often sorts it; stopping it quietly means the anaemia comes back. Expect to feel better within two to four weeks, but keep going for the months it takes to refill the stores, and have a repeat blood test to confirm.
How to absorb more iron
- Take iron with vitamin C: a glass of orange juice, or a vitamin C tablet. It can double absorption.
- Keep tea and coffee an hour away from iron, whether tablets or a steak. Tannins block it. The same goes for milk, calcium supplements and antacids.
- Eat the iron-rich foods: red meat, liver (not in pregnancy), sardines, eggs, lentils and beans, tofu, dark leafy greens, dried apricots, fortified cereals. Animal (haem) iron is absorbed several times better than plant iron, so vegetarians need the vitamin C trick more.
- Don't take iron with other minerals in the same gulp; zinc and calcium compete for the same route in.
- Treat the cause. Heavy periods can be made lighter; a gut that bleeds needs looking at. Supplements alone are bailing a boat with a hole in it.
When to see a GP
If you have the symptoms above, see a GP for the blood test rather than self-treating; it's quick and it rules out the things that matter. See one promptly if you're a man or a post-menopausal woman with suspected low iron, you have black or bloody stools, unexplained weight loss, or you're pregnant. Untreated iron deficiency anaemia raises the risk of infections, heart strain and, in pregnancy, a low-birth-weight baby. Our pharmacist can help you choose a supplement that suits your stomach and your other medicines.
Frequently asked questions
Can iron deficiency cause hair loss?
Yes. Low ferritin is one of the commonest reversible causes of diffuse hair shedding in women. Hair regrows over months once stores are rebuilt.
How long does it take to raise iron levels?
Haemoglobin improves within a few weeks of prescription iron; ferritin stores take three to six months. Low-dose supplements work on the same timescale but more slowly.
Is liquid iron better than tablets?
Gentler, not stronger. Liquid iron is easier on the stomach and well absorbed, but delivers a fraction of the dose of ferrous sulfate, so it's for topping up and maintaining, not for treating diagnosed anaemia unless a GP agrees.
Can you take too much iron?
Yes, and it's dangerous for children, who can be poisoned by a handful of adult tablets. Keep iron out of reach, and don't exceed the pack dose without a blood test showing you need it.
Do I need extra iron in pregnancy?
Many women do, especially in the second and third trimesters, and routine antenatal bloods check for it. If your levels are fine, a pregnancy multivitamin with iron or a gentle supplement such as Spatone covers the extra demand; if they're low, your midwife will arrange prescription iron.
Should vegans take an iron supplement?
Not automatically, but it's worth a blood test every year or two, since plant iron is absorbed less well. Pairing iron-rich foods with vitamin C at every meal, and keeping tea and coffee away from them, is often enough; a low-dose daily supplement is sensible insurance if ferritin is drifting down.