Iron Tablets: Who Needs Them, How to Take Them and Side Effects (UK)

Who needs iron tablets?

Iron tablets treat iron deficiency anaemia or low iron stores (ferritin) found on a blood test. The NHS says that if you feel tired but haven’t been diagnosed, talk to your doctor or pharmacist before taking iron, as there may be other reasons you lack energy. See why am I always tired? and the signs in iron deficiency symptoms.

Finding the cause matters too. Heavy periods and pregnancy are very common causes, and bleeding in the gut is another. The British Society of Gastroenterology says about a third of men and postmenopausal women with iron deficiency anaemia have an underlying problem, most often in the gut, so your GP may arrange further tests. For heavy periods, see period pain relief.

The NHS says 17mg or less a day of iron from supplements is unlikely to cause harm, but continue a higher dose if a GP has advised it.

Iron tablets in the UK

Over the counter iron tablets in the UK

Pharmacies sell ferrous sulfate (200mg tablets or drops) and ferrous fumarate (tablets, capsules or liquid) without a prescription. A pharmacy ferrous sulfate 200mg tablet is the same strength as the usual prescribed one. For food supplements, compare the elemental iron on the label with the NHS 17mg figure. Don’t self-treat suspected anaemia: a blood test confirms it and helps find the cause.

Iron tablets for anaemia

iThe NHS says your GP will usually do a full blood count, look for the cause (such as heavy periods or an ulcer), then recommend iron tablets for about 6 months, with repeat blood tests. Iron injections are an option if tablets don’t help. See low iron symptoms.

Iron supplements for women

Women aged 19 to 49 need 14.8mg of iron a day, against 8.7mg for men. The NHS says women with heavy periods are at higher risk of iron deficiency anaemia and may need iron supplements, so ask your GP for a blood test (see why am I so tired on my period). In pregnancy, your midwife or GP may recommend iron if blood tests show low levels.

Types of iron tablet compared

The strength on the box (for example 200mg) is the iron salt. What matters is the elemental iron it contains.

Figures from the BNF. The NHS and BNF say there is little difference between ferrous salts at the same dose of iron, though a side effect with one type may not happen with another. You may also see ferrous bisglycinate in shops: a 2023 review of 17 trials found fewer gut side effects and higher haemoglobin than other iron in pregnant women, but too few trials in other adults to say.

How to take iron tablets

How long after iron tablets can I drink tea or coffee?

Two hours. The NHS ferrous sulfate page says to “leave a 2 hour gap before having tea or coffee”, dairy or eggs, as they can stop your body absorbing iron. Herbal teas and cocoa may matter too: in a 1999 study of iron from a meal, black tea cut absorption by 79% to 94%, peppermint tea by 84%, cocoa by 71% and camomile tea by 47%.

The NHS says your doctor or pharmacist may suggest orange juice or a vitamin C supplement to help absorption. It’s optional: in a trial of 440 adults with iron deficiency anaemia, iron alone worked as well as iron plus vitamin C. More on vitamin C, and on fitting iron around your morning coffee.

Best time to take iron tablets: daily or every other day?

There’s no single best time of day. NICE CKS suggests an empty stomach, and the studies below gave iron first thing in the morning before food. If that makes you feel sick, taking it with a meal beats skipping it. Every other day is now an option in UK guidance. The research:

• A single iron dose raises hepcidin, a hormone that blocks iron absorption, for about 24 hours. In a 2015 study of 54 women with low iron, absorption from the next day’s dose fell by 35% to 45%.
• In a 2017 trial in 40 iron-depleted women, alternate days for 28 days gave more iron absorbed in total than daily doses for 14 days. Splitting the dose twice a day didn’t help.
• A 2020 study in 19 women with iron deficiency anaemia found absorption was 40% to 50% higher after a day off than on a second day in a row.

iThese were small absorption studies, and NICE CKS says the best timing is not clearly defined. The NHS and BNF say your doctor may switch you to alternate days if you get side effects, so check before changing.

Iron tablet side effects and how to cope

A review of 43 trials found ferrous sulfate roughly doubled the odds of gut side effects compared with a placebo. The NHS lists these, with tips:

• Feeling sick, stomach pain or heartburn: take the tablet with or just after a meal or snack, and stick to simple meals.
• Constipation: more fibre, plenty of water and a daily walk. A GP can offer a laxative; if it contains magnesium, ask your pharmacist about the gap. See magnesium for constipation.
• Diarrhoea: drink plenty of fluids and ask a pharmacist before taking anything to stop it.
• Darker poo: common with iron and usually nothing to worry about.
• Losing your appetite: smaller meals more often. See breakfast for energy.

NICE CKS says side effects usually settle with time. If not, your GP may suggest alternate days, another preparation or iron injections, usually given in hospital.

Call 111 straight away if your poo is black and tar-like or red, or has blood in it, or you feel unwell. Call 999 if your face, lips or throat swell or you struggle to breathe.

How long do iron tablets take to work?

The NHS says most people start to feel better after 3 to 4 weeks, but it may take 2 to 4 months for iron tablets to work fully. Your GP will usually repeat your blood test within the first 4 weeks. NICE CKS says haemoglobin should rise by about 20g/L over 3 to 4 weeks.

How long to take them: NICE CKS and the BNF advise about 3 more months once your blood count is normal, to refill your stores; the NHS says 3 to 6 months after you’ve improved, so follow your GP’s plan. Don’t take shop-bought ferrous fumarate for longer than 6 months without seeing a GP. Still tired once your iron is normal? Ask about vitamin B12 deficiency or an underactive thyroid.

Medicines and supplements to space apart from iron

Iron can stop some medicines being absorbed properly, and some medicines reduce how much iron you absorb. Gaps from the BNF:

• Antacids and indigestion remedies: take iron 1 hour before or 2 hours after.
• Calcium carbonate: take it 1 hour before or 2 hours after iron. See magnesium and calcium.
• Tetracycline antibiotics such as doxycycline and lymecycline: take the antibiotic 2 to 3 hours after iron.
• Quinolone antibiotics such as ciprofloxacin and levofloxacin: at least 2 hours apart.
• Levothyroxine for an underactive thyroid: at least 4 hours apart.
• Others include osteoporosis medicines (risedronate, alendronic acid), levodopa, penicillamine, mycophenolate and some HIV medicines.
• Zinc, calcium and magnesium supplements: the NHS asks you to tell your pharmacist before starting iron, and iron can stop zinc working as well. See zinc.

In a large US study, taking proton pump inhibitors such as omeprazole for 2 years or more was linked to iron deficiency. Don’t stop them yourself, but mention them to your GP if your iron stays low.

Safety and who should not take iron tablets

Tell your doctor before taking ferrous sulfate if you have:

• Haemochromatosis or another iron overload condition. The NHS advises people with haemochromatosis to avoid iron and vitamin C supplements.
• A different type of anaemia, or a red blood cell condition such as sickle cell anaemia or thalassaemia.
• A stomach ulcer, inflammatory bowel disease or past stomach surgery.
• Regular blood transfusions, or blood in your pee.

If you’re pregnant or breastfeeding, follow your midwife’s or GP’s advice on iron. Iron doesn’t affect contraception, but sickness or severe diarrhoea for over 24 hours can stop the pill working.

Iron from food

If a blood test shows anaemia, the NHS recommends iron tablets alongside iron-rich foods, not food alone. Once your levels are back to normal, a good diet helps keep them there. The NHS suggests eating more dark green leafy vegetables, fortified cereals and bread, meat, pulses and dried fruit, and less tea, coffee and dairy around meals. Our guide to iron-rich foods has amounts per portion and tips for vegetarians, and supplements for women over 40 covers iron as periods change.

Does Evopure sell iron?

No. Evopure doesn’t make an iron supplement, and if you’re low in iron you need the dose your GP prescribes. Iron contributes to the reduction of tiredness and fatigue, and to normal formation of red blood cells and haemoglobin.

If you also take our Magnesium Glycinate Sleep Complex, a bedtime drink, keep the two at opposite ends of the day (iron in the morning, magnesium in the evening) and ask your pharmacist about the gap. Our Reishi hot chocolate contains cacao, so keep it 2 hours from an iron tablet too. Magnesium contributes to a reduction of tiredness and fatigue. See best time to take magnesium and best supplements for energy. Our products are for adults only, and we don’t recommend them during pregnancy or breastfeeding.

See also how to take calcium supplements around iron and other medicines.

Low ferritin can trigger restless legs; see magnesium vs iron for restless legs.

iIf you have restless legs, ask your GP about your ferritin; see iron and restless legs.

Related guides

• Foods that help constipation if iron tablets bung you up.
• If you take zinc and magnesium as well, see can you take zinc and magnesium together for timing.
• Iron is the supplement most dangerous to children in overdose; see vitamin overdose: what to do.