Iron

Iron is needed to make haemoglobin, the protein in red blood cells that carries oxygen from the lungs to the rest of the body. When iron runs low, the body cannot make enough working red blood cells. The result is iron deficiency anaemia, the most common nutritional deficiency in the UK. Persistent tiredness, breathlessness during light exertion, and a noticeable heartbeat are the usual first signs.

Iron also sits inside myoglobin, which carries oxygen to muscles, and it plays a role in immune defence and brain development. The body holds about 4 grams of iron in total, most of it bound into red blood cells, with smaller stores in the liver, spleen, and bone marrow that get drawn on when intake from food drops.

Two forms of iron behave very differently in food. Haem iron is bound into the haemoglobin and myoglobin of animal tissue, and is absorbed efficiently regardless of what else is on the plate. It is found in meat, poultry, and fish. Non-haem iron is the form in plant foods (beans, lentils, tofu, dark green leaves, nuts, seeds), in eggs, and in fortified breakfast cereals. On its own it absorbs less well, but absorption rises sharply when vitamin C (citrus, peppers, tomatoes, kiwifruit) is in the same meal. Tea, coffee, and the calcium in dairy reduce absorption when taken at the same time, so tea after the meal rather than with it is a small practical step that adds up.

Iron is in a wide range of UK foods. Meat and fish carry haem iron, the more absorbable form. Pulses, dark leafy greens, tofu, nuts, seeds, eggs, and fortified breakfast cereals carry non-haem iron, which absorbs better with vitamin C in the same meal.

The table is ranked by iron content per typical UK portion. Values per 100g come from USDA SR Legacy and McCance and Widdowson 7th edition. Percentages of the adult RNI use 14.8mg as the basis, the UK figure for women aged 19 to 50. For men, and women aged 50 and over, the RNI is 8.7mg, so the percentages would be roughly double.

Practical tips for non-haem iron absorption:

• Add a vitamin C source to the meal: a squeeze of lemon on the lentil dhal, peppers in a stir-fry with tofu, an orange after the beans on toast.
• Move tea and coffee away from mealtimes by an hour either side.
• If you take a calcium supplement, take it between meals rather than with the iron-rich one.

Liver: lamb's liver carries around 10mg of iron per 100g, the highest single source. NHS advice is not to eat liver more than once a week because of its high vitamin A content, and pregnant women are advised to avoid liver entirely for the same reason.

The UK Reference Nutrient Intake (RNI) for iron is set by SACN (1991 Dietary Reference Values) and is the value reproduced by the NHS. Values are mg per day.

Why the women's RNI is higher than the men's: menstrual blood loss. The 14.8mg figure for women aged 19 to 50 accounts for average losses; women with heavy periods often need more, and a GP can advise on supplementation when iron stores are low.

Why pregnancy carries no formal increment: SACN concluded that the extra demand of pregnancy is normally met by the rise in iron absorption and by drawing on stored iron. Women who enter pregnancy with low stores may still need a supplement, and any anaemia diagnosed during pregnancy is treated. Iron is not part of the routine NHS Healthy Start vitamin pack (which contains folic acid, vitamin D, and vitamin C), but the antenatal team will advise on iron if blood tests show a need.

Iron deficiency runs along a spectrum, from low iron stores (no symptoms yet) to iron deficiency anaemia (symptoms apparent). Once anaemia sets in, the classic signs are:

• Tiredness and lack of energy
• Breathlessness on mild exertion (climbing stairs, walking briskly)
• Noticeable heartbeat (palpitations)
• Pale skin, especially noticeable on the inside of the eyelid
• Headache
• Restless legs
• Brittle nails, sometimes spoon-shaped (koilonychia)
• Cracks at the corners of the mouth
• Sore or smooth tongue
• Hair thinning or loss
• Cravings for non-food substances such as ice or earth (pica)

The symptoms can build slowly and are easy to put down to a busy life. Persistent tiredness is reason enough to see a GP and ask for a blood test, especially if you are in one of the higher-risk groups below.

Who is at higher risk in the UK

• Women with heavy periods. The single largest contributor to iron deficiency in UK women under 50.
• Pregnant women. Iron demand rises during pregnancy. Women starting pregnancy with low stores are checked by the antenatal team.
• Women aged 19 to 50 generally. The 14.8mg RNI is genuinely hard to hit from a typical UK diet without conscious meal planning.
• Adolescent girls aged 11 to 18. The same 14.8mg RNI applies. National diet surveys repeatedly show this age group with the lowest average intakes.
• Vegetarians and vegans. Non-haem iron absorbs less efficiently. Hitting the RNI is doable with planning (pulses, tofu, fortified cereal, seeds, dark green leaves, vitamin C with meals), but takes attention.
• Frequent blood donors. Each donation removes around 220 to 250mg of iron. NHS Blood and Transplant monitors haemoglobin at every donation.
• People with coeliac disease, inflammatory bowel disease, or after gastric surgery. Absorption is reduced and routine GP follow-up is standard.
• Older adults. Lower stomach acid, more medications interacting with iron absorption, and reduced appetite all play in.
• Endurance athletes. Iron loss through sweat and microscopic gut bleeding from heavy training adds up.

When to see your GP: persistent tiredness, breathlessness, palpitations, or any of the symptoms above, especially if you are in one of the risk groups. The GP will order a blood test for haemoglobin and usually for ferritin (the iron storage protein). Iron deficiency without an obvious cause in men, or in women over 50, is investigated further because it can be the first sign of bleeding from elsewhere in the body.

This page is reference information, not medical advice. Always check with a healthcare professional before starting iron supplements at therapeutic doses.

It is very hard to take iron from food alone to harmful levels in a healthy adult. The risk is from supplements, especially high-dose ones taken without medical advice.

NHS supplement guidance: taking 17mg or less a day of iron from supplements is unlikely to cause harm.

Side effects rise as the dose rises. Common at higher doses (typical prescription-strength iron tablets contain 65 to 200mg of elemental iron per tablet):

• Constipation, or diarrhoea
• Stomach pain, indigestion
• Nausea
• Black or very dark stools (this is normal at therapeutic doses, not a cause for alarm in itself)

If a doctor has prescribed an iron supplement, taking it with a vitamin C source (orange juice, fruit) on an empty stomach maximises absorption but increases the chance of stomach side effects. Taking it with food reduces side effects but also reduces absorption. The GP or pharmacist will advise on the right balance for the individual.

Children: iron supplements at adult doses can be life-threatening to young children. Keep iron tablets in a child-resistant container out of reach.

Hereditary haemochromatosis: a fairly common UK genetic condition in which the body absorbs too much iron. People with the condition (or who have a family member affected) need to avoid iron supplements and ferritin-rich foods such as liver, and are managed through regular venesection (blood letting) by the NHS. A GP can arrange testing if a family member is affected.

The NHS position on iron is that most people should be able to get enough from a varied diet. Supplements are recommended in specific situations only, and always at the lowest dose needed.

NHS over-the-counter guidance: 17mg or less a day of iron in a supplement is unlikely to cause harm.

When iron supplements are indicated:

• Iron deficiency anaemia confirmed by blood test. Treatment is usually a prescription-strength iron tablet (such as ferrous sulphate, ferrous fumarate, or ferrous gluconate) under GP supervision, with a follow-up blood test after 2 to 4 months.
• Pregnancy where blood tests show low iron stores. The antenatal team will advise.
• Heavy periods that are leaving you regularly anaemic, alongside treatment of the underlying cause.
• Following GP or dietitian advice in coeliac disease, inflammatory bowel disease, or after gastric surgery.

When iron supplements are not recommended without medical advice:

• For general tiredness that has not been investigated. Tiredness has many causes; supplementing iron blindly can mask an underlying condition.
• For people with hereditary haemochromatosis or any condition that causes iron overload.
• For young children, unless prescribed.

Vegetarian and vegan iron: the NHS does not recommend automatic supplementation for vegetarians or vegans, but does recommend paying attention to non-haem iron sources (pulses, tofu, fortified breakfast cereal, dark green leaves, nuts and seeds, dried fruit) and to vitamin C alongside meals. A blood test, if there are symptoms, gives a clear picture.

How to take iron tablets: with a vitamin C source (a glass of orange juice, or fruit) for best absorption, on an empty stomach if tolerated, and at least an hour before or two hours after tea, coffee, or calcium-rich foods.

• Vegetarian and vegan iron sources: Plant-based eating covers iron, B12, and the other nutrients that need attention on a meat-free diet.
• Pulses for non-haem iron: Lentils and Chickpeas are the most efficient affordable UK sources.
• The other nutrient behind anaemia: Vitamin B12. Iron deficiency anaemia and B12 deficiency anaemia have overlapping symptoms but very different causes; a blood test distinguishes them.

• NHS. Vitamins and minerals: Iron. nhs.uk/conditions/vitamins-and-minerals/iron. Adult RNIs, supplement guidance, and deficiency information.
• Scientific Advisory Committee on Nutrition (SACN). Dietary Reference Values for Food Energy and Nutrients for the United Kingdom. Department of Health Report on Health and Social Subjects 41 (1991). The source of the age-banded UK RNIs reproduced above.
• NHS. Iron deficiency anaemia: Causes, symptoms, and treatment. nhs.uk/conditions/iron-deficiency-anaemia.
• National Diet and Nutrition Survey (NDNS), rolling programme. Public Health England / OHID. The source for UK population-level iron-intake data in adolescent girls and women aged 19 to 64.
• Public Health England. McCance and Widdowson's The Composition of Foods, 7th summary edition (2015). The UK food composition reference used alongside USDA SR Legacy for the per-100g iron values in the food table.
• USDA Agricultural Research Service. FoodData Central, SR Legacy release. fdc.nal.usda.gov. Used for the per-100g iron values where M&W is silent or where the US value is more recent and consistent.

This page is reference information for UK shoppers. It is not medical advice. Persistent symptoms or any concern about iron stores should be checked with a GP or registered dietitian.