Compare iron tablets, liquids and sprays on what you actually get: the amount of iron per daily dose and the cost per day. The NHS says 17mg or less a day from supplements is unlikely to cause harm, and very high doses can be fatal for children, so keep iron out of their reach.
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How much iron do you need a day?
The NHS says you need 8.7mg of iron a day if you're a man aged 19 or over, 14.8mg a day if you're a woman aged 19 to 49, and 8.7mg a day if you're a woman aged 50 or over. It says taking 17mg or less a day of iron supplements is unlikely to cause any harm, but if your GP has advised a higher dose, keep taking it.
Good food sources include red meat, beans and pulses such as kidney beans, edamame and chickpeas, nuts, dried fruit such as apricots, fortified breakfast cereals and soy flour. Liver is also rich in iron, but the NHS says to avoid it during pregnancy.
Are iron supplements dangerous for children?
Yes, they can be. The NHS warns that very high doses of iron can be fatal, particularly if taken by children. Keep iron supplements, and any multivitamin containing iron, out of the sight and reach of children.
Iron tablets can look like sweets, and some iron products are flavoured. Iron supplements for children should be discussed with a GP or pharmacist first.
What does %NRV mean on iron tablets?
%NRV compares the iron in a daily dose with a standard reference amount. The NRV for iron is 14mg, so a 14mg tablet shows as 100% NRV.
| Iron per daily dose | %NRV | How it compares with NHS advice |
|---|---|---|
| 8.7mg | 62% | The daily amount for men, and women aged 50 and over |
| 10mg | 71% | Within the NHS 17mg supplement figure |
| 14.8mg | 106% | The daily amount for women aged 19 to 49 |
| 17mg | 121% | The most the NHS says is unlikely to cause harm from supplements |
| 20mg | 143% | The NHS says doses over 20mg can cause side effects |
"We want customers to understand what they're taking rather than simply choosing the highest numbers on the label," says Andy Arshad, who runs SupplementHQ. Our guide to reading a supplement label explains more.
What are the side effects of iron tablets?
The NHS says high doses of iron (over 20mg) can cause constipation, feeling sick, being sick and stomach pain. For prescribed iron tablets, it also lists diarrhoea, heartburn and darker than usual poo as possible side effects.
Iron also appears in many multivitamins and women's formulas, so add up the iron across everything you take. Speak to your GP or pharmacist before taking iron if you have a medical condition or take medication.
How do you know if you need iron tablets?
Only a blood test can tell you whether you're low in iron. The NHS says symptoms of iron deficiency anaemia include tiredness and lack of energy, shortness of breath, noticeable heartbeats, paler than usual skin and headaches, and that you should see a GP if you think you might have it.
The NHS says heavy periods and pregnancy are very common causes. If a GP confirms iron deficiency anaemia, they will usually recommend iron tablets, often for around six months. If you suspect anaemia, speak to your GP before buying a supplement.
Do women need more iron?
Yes, women aged 19 to 49 need more iron than men, and the British Dietetic Association says UK dietary surveys indicate that many women are not getting enough iron. If you menstruate or are pregnant, you may need more.
In pregnancy, the BDA says a doctor will usually check your iron levels and may recommend supplements if there is a risk of anaemia. Speak to your midwife or GP before taking iron. The NHS advises 400 micrograms of folic acid every day from before you're pregnant until you're 12 weeks pregnant, and a daily vitamin D supplement, and says not to take cod liver oil or any supplements containing vitamin A (retinol) when you're pregnant. See prenatal & fertility and women's health.
When is the best time to take iron tablets?
Follow the directions on your product's label or your GP's advice. What you eat and drink at the same time can make a difference to how much iron you absorb.
The BDA says tea and coffee contain tannins, which make iron harder to absorb, and that eating plant iron with foods containing vitamin C can help. Vitamin C has the authorised claim "Vitamin C increases iron absorption". Browse vitamin C.
Tablets, liquid or spray iron?
Choose the format you'll take consistently, then compare the iron per daily dose and the cost per day. This collection includes iron capsules and tablets, liquid iron, a 10mg daily oral spray and liposomal iron (iron wrapped in tiny fat-based bubbles).
Where a product is at least a source of iron, authorised claims include "Iron contributes to normal formation of red blood cells and haemoglobin" and "Iron contributes to the reduction of tiredness and fatigue".
"Two products that look almost identical on the shelf can offer different value," says Andy.
How to compare value (example figures, not real products): a £6 pot of 90 tablets with 14mg of iron, one a day, costs about 7p a day. A £15 oral spray giving 30 daily doses of 10mg costs 50p a day, about seven and a half times as much for less iron.
Which is the best iron supplement?
The best one for you depends on whether you've been advised to take iron, how much you need, and which format you can take without side effects. If your GP has prescribed iron, follow their advice rather than switching to a supplement.
For general use, compare the iron per daily dose against the NHS 17mg figure, then the cost per day. If you're unsure what you need, our guide to what supplements you actually need is a good place to start, or go back to all vitamins & supplements.
We sell the products on this page. That's our commercial interest, and it's why we show the evidence alongside them. This page is general information for adults, not personalised medical advice. Food supplements should not replace a varied, balanced diet.
Written by Andy Arshad, SupplementHQ. Last reviewed 11 October 2026.