Iron
Iron supplements in tablets, capsules, liquid and gummies, from gentle bisglycinate to ferrous fumarate. We explain which form suits a sensitive stomach, how vitamin C helps absorption and the UK daily amounts.Read more →
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Choosing an iron supplement your body can actually absorb
Iron is a mineral your body uses to build haemoglobin, the red pigment in blood that carries oxygen from your lungs to the rest of the body. Iron contributes to the reduction of tiredness and fatigue, and to normal energy-yielding metabolism, normal cognitive function and the normal function of the immune system.
Two kinds of dietary iron, two rates of absorption
Food supplies iron in two forms. Haem iron, from red meat and fish, is taken up readily. Non-haem iron, from lentils, beans, tofu, dark leafy greens and fortified bread, is absorbed far less efficiently. Tea, coffee and calcium reduce that uptake further. This is the practical reason iron sits among the more commonly supplemented items in our wider mineral range, especially for people who eat little meat.
The number on the label is not always the iron you get
Iron is always bound to another compound, and only part of that weight is iron your body can use. That part is called elemental iron, and it is the figure you should compare between products. The forms you will find here:
- Ferrous fumarate and ferrous sulphate: long-established, well studied, usually the cheapest per milligram. Also the forms most often linked with constipation and nausea.
- Iron bisglycinate: iron attached to the amino acid glycine. Frequently labelled gentle or non-constipating because less free iron is left in the gut.
- Iron pyrophosphate: often used in liquids and drinks, chosen for a milder taste and low irritation.
- Liquid iron and sachets: easy to take for anyone who struggles with tablets, and simple to split into smaller doses.
- Gummies and drops: lower-dose formats, mainly for children and teenagers.
Because vitamin C improves uptake of non-haem iron, many formulas pair the two. If yours does not, a separate vitamin C product taken at the same moment does the same job.
How we choose the iron we stock
We look at three things: the form, the dose in elemental iron, and whether the combination makes sense. We keep gentler forms such as bisglycinate for sensitive stomachs and classic ferrous salts for people who tolerate them well, because there is no single right answer. We prefer vitamin C in the formula over long ingredient lists that add nothing. We are brand-neutral: we stock what works, not what pays best. Every product passes our compliance team, we test products ourselves and independent labs spot-check batches. You can read how we select brands and products.
Who it suits, and what to expect
Iron is most often used by people with heavier periods, by those following vegan and vegetarian diets, by endurance athletes, and by regular blood donors. Most people in the UK can reach their daily iron from a varied diet, so a supplement is best seen as filling a genuine gap rather than a routine addition.
Be patient and realistic. Iron stores rebuild slowly: expect weeks rather than days, and often two to three months of consistent use before blood values shift. Dose matters more than brand. NHS guidance is that supplements providing 17 mg a day or less are unlikely to cause harm, while side effects become more common above 20 mg. Higher amounts belong under GP supervision, ideally after a blood test. Keep iron out of reach of children, since accidental overdose is genuinely dangerous.
Frequently asked questions
Iron is a building block of haemoglobin, the protein in red blood cells that moves oxygen from your lungs to your muscles, brain and organs. Because almost every cell depends on that oxygen supply, iron shows up in several approved statements: it contributes to normal formation of red blood cells and haemoglobin, to normal oxygen transport, to normal energy-yielding metabolism, to normal cognitive function, to normal immune function and to the reduction of tiredness and fatigue.
Guessing from tiredness alone is unreliable, because tiredness has many causes. The dependable route is a blood test: your GP can check haemoglobin and ferritin, the marker that reflects stored iron. Groups more likely to run low are people with heavy periods, vegans and vegetarians, pregnant women, teenagers in a growth spurt, endurance athletes and regular blood donors. If your diet already includes meat, fish and fortified bread, a supplement may add little.
There is no universally best form. The decision usually comes down to how your stomach reacts and how you prefer to take it.
| Form | Character | Suits |
|---|---|---|
| Ferrous sulphate | Classic, low cost | Strong tolerance |
| Ferrous fumarate | Well studied, potent | Rebuilding stores |
| Iron bisglycinate | Gentle, chelated | Sensitive stomachs |
| Iron pyrophosphate | Mild, near tasteless | Liquids and drinks |
| Liquid or sachets | Flexible dosing | Tablet avoiders |
| Gummies | Lower dose | Children, teenagers |
Compare the elemental iron figure, not the compound weight, when you weigh two products against each other.
The UK reference intakes differ by sex and age, mainly because of menstrual blood loss. Supplement labels usually show the EU Nutrient Reference Value of 14 mg instead, which is a single average figure rather than a personal target.
| Group | Iron per day |
|---|---|
| Men 19+ | 8.7 mg |
| Women 19 to 49 | 14.8 mg |
| Women 50+ | 8.7 mg |
Women still having periods after 50 may need the higher amount.
Source: NHSUptake is highest on an empty stomach, so many people take iron in the morning, roughly an hour before breakfast. Add a glass of orange juice or a vitamin C product, since vitamin C improves absorption of non-haem iron. Keep tea, coffee, milk and calcium supplements at least an hour away, because tannins and calcium reduce uptake. If an empty stomach makes you feel sick, take it with a light meal instead.
Your gut absorbs only part of a dose. The rest travels on and can irritate the bowel lining, which shows up as constipation, nausea or dark stools. Dark stools are harmless. Three things usually help: choose a gentler form such as bisglycinate, drop to the lowest dose that still meets your need, and drink plenty of water with fibre-rich food. A liquid also lets you build up gradually rather than starting high.
Iron intake raises a hormone called hepcidin, which acts as a brake on further absorption and stays elevated for around a day. Research in iron-depleted women found that spacing doses to alternate days raised the percentage of iron absorbed and tended to cause less nausea. For everyday maintenance amounts the practical difference is small, so consistency matters more. If you are on a higher dose from your GP, follow their schedule and raise the idea with them.
Iron needs rise in pregnancy because blood volume increases, and many prenatal formulas in our pregnancy and breastfeeding range already include iron. Check the label before adding a second iron product, so the amounts do not stack up unnoticed. Discuss extra iron with your midwife or GP, who can test your levels first. One separate UK point: avoid liver and liver products in pregnancy, since their vitamin A content is too high.
Yes. People with haemochromatosis, an inherited condition in which the body stores too much iron, should not supplement unless a doctor says so. The same caution applies with repeated blood transfusions or certain chronic conditions. Iron also interacts with some medicines, including thyroid hormone and several antibiotics, so spacing doses by a few hours is often advised. Because very high amounts are dangerous for young children, always store iron out of their reach.
