Iron

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By Nikola · Precision Nutrition L1 · Updated 5 November 2026

Iron is an essential mineral that the body needs to make haemoglobin and red blood cells, carry oxygen and support normal energy metabolism; heavy periods and pregnancy are very common reasons for running low. EFSA sets a population reference intake of 11 mg a day for men and for women after menopause, and 16 mg for women who have periods, including in pregnancy and breastfeeding. Haem iron from meat, fish and seafood is absorbed better than non-haem iron from pulses, seeds, leafy greens and fortified foods. Supplements are the standard treatment for a diagnosed deficiency, but do not start iron without a blood test: the symptoms are vague, a deficiency can point to bleeding that needs a cause found, and too much iron is harmful, especially for small children.

What the research says

• Treating iron deficiency anaemia (strong, standard treatment). When a blood test shows low red blood cells from iron deficiency, GPs usually prescribe iron tablets for about 6 months (NHS).
• Heavy periods and pregnancy. The NHS calls them very common causes of iron deficiency anaemia. For pregnancy, the US RDA rises to 27 mg while EFSA keeps 16 mg, assuming iron stores and better absorption cover the extra need. In pregnancy, follow your antenatal blood tests and advice.
• Frequent blood donors. Men with at least three and women with at least two donations in the past year were more than five times as likely to have depleted iron stores as first-time donors (NIH).
• Tiredness without a deficiency (not shown). The EU allows foods that are a source of iron to say “Iron contributes to the reduction of tiredness and fatigue”. This describes iron’s normal role, not proof that extra iron gives energy when your levels are normal.
• Other EU-authorised claims (Regulation (EU) 432/2012): iron contributes “to normal cognitive function”, “to normal energy-yielding metabolism”, “to normal formation of red blood cells and haemoglobin”, “to normal oxygen transport in the body” and “to the normal function of the immune system”, and “has a role in the process of cell division”.

Dose and forms

Group	EFSA PRI, mg a day	EFSA safe level of intake	For reference: US RDA
Men	11	40 mg	8 mg
Women with periods	16	40 mg	18 mg (19-50 years)
Women after menopause	11	40 mg	8 mg (51+)
Pregnancy	16	40 mg	27 mg
Breastfeeding	16	40 mg	9 mg
Children 1-6 years / 7-11 years	7 / 11	10 mg (1-3 years), 15 mg (4-6), 20 mg (7-10)	–
Teenagers 12-17: girls / boys	13 / 11	30-35 mg	–

Source: EFSA NDA Panel (2015 and 2024); EFSA overview of upper intake levels (version 11, 2025); NIH ODS for the US RDA. In 2024 EFSA could not set a classic upper limit (UL) for iron and set a “safe level of intake” of 40 mg a day for adults instead, including pregnancy and breastfeeding. The US upper limit is 45 mg, and vegetarians may need 1.8 times the RDA because plant iron is absorbed less (NIH). The NHS says 17 mg or less a day from supplements is unlikely to cause harm.

Forms. Ferrous (iron II) salts are absorbed better than ferric (iron III) forms. Elemental iron is about 33% of ferrous fumarate, 20% of ferrous sulfate and 12% of ferrous gluconate (NIH), so compare elemental iron, not the weight of the salt. Iron-only products often contain 65 mg (NIH), several times the daily reference intake.

Food sources

Food	Iron, 100 g	Portion	Iron per portion
White beans, boiled	3.70 mg	1 cup, 179 g	6.6 mg
Lentils, boiled	3.33 mg	1 cup, 198 g	6.6 mg
Spinach, boiled	3.57 mg	1 cup, 180 g	6.4 mg
Oysters, eastern, farmed, raw	5.78 mg	6 medium, 84 g	4.9 mg
Chickpeas, boiled	2.89 mg	1 cup, 164 g	4.7 mg
Tofu, firm	2.66 mg	½ cup, 126 g	3.4 mg
Sardines, canned in oil	2.92 mg	1 tin, 92 g	2.7 mg
Pumpkin seeds, dried	8.82 mg	28 g	2.5 mg
Ground beef, 80% lean, raw	1.94 mg	113 g raw	2.2 mg
Sesame seeds, whole	14.6 mg	1 tbsp, 9 g	1.3 mg

Source: USDA FoodData Central, SR Legacy, checked 5 November 2026: white beans FDC 175203, lentils FDC 172421, spinach boiled FDC 168463, oysters FDC 175172, chickpeas FDC 173757, tofu FDC 172475, sardines FDC 175139, pumpkin seeds FDC 170556, ground beef FDC 174036, sesame seeds FDC 170150. Values per portion are calculated from USDA household measures and rounded.

From mixed diets with meat, fish and vitamin C the body absorbs about 14-18% of iron, from vegetarian diets about 5-12% (NIH). Three habits help with plant iron:

• Add vitamin C to the meal. It improves iron absorption from plant foods (NIH): bell peppers, lemon juice over lentils, kiwi, broccoli, tomatoes.
• Go easy on tea and coffee. The NHS advises people with iron deficiency anaemia to cut down on tea, coffee and milk, and notes that phytic acid in wholegrains also lowers absorption.
• Combine. A little meat, fish or seafood with white beans or chickpeas also improves non-haem iron absorption (NIH). Spinach, tofu and pumpkin seeds are good plant options.

Side effects and interactions

• Stomach and bowel. Constipation, nausea, vomiting and stomach pain at high doses (over 20 mg, NHS; 45 mg or more, NIH), and dark stools with iron tablets.
• Danger for children. The FDA warning label reads: “Accidental overdose of iron-containing products is a leading cause of fatal poisoning in children under 6.” At least 43 US children died from swallowing high-dose iron between 1983 and 2000 (NIH). Keep all iron products out of children’s reach, as the NHS also warns.
• Haemochromatosis. This inherited condition makes the body absorb too much iron and, untreated, can damage the liver and heart; people with it should avoid iron and vitamin C supplements (NIH).
• Medicines. Iron can reduce the effect of levothyroxine (labels advise at least 4 hours apart) and the absorption of levodopa. Proton pump inhibitors such as omeprazole lower non-haem iron absorption, and supplements may work less well while you take them (NIH).
• Zinc. Iron supplements of 25 mg or more can reduce zinc absorption.

Who should avoid it

• Anyone without a blood test showing low iron. Tiredness has many causes, and iron “just in case” can hide a problem such as bleeding in the stomach or bowel, a common cause of iron deficiency anaemia (NHS).
• Men and women after menopause without a diagnosed deficiency: their reference intake is 11 mg a day, lower than the 16 mg for women with periods.
• People with haemochromatosis or other iron overload, and children unless a doctor sets the dose.
• People on levothyroxine, levodopa or long-term acid blockers, unless a doctor or pharmacist has agreed the timing.

How to choose a good product

• Follow the prescribed dose. Dose and length of treatment come from your blood results, not the label.
• Read elemental iron per tablet and add multivitamins, which for women often contain 18 mg (NIH).
• Choose child-resistant packaging and store it out of reach.
• Look for independent testing. Seals from U.S. Pharmacopeia, NSF International or ConsumerLab.com show a product contains what the label says and no harmful levels of contaminants; the NIH notes they do not prove safety or effect. We do not recommend brands or link to shops.

FAQ

What are the symptoms of low iron?

The NHS lists tiredness and lack of energy, shortness of breath and paler skin than usual. Many conditions cause these signs, so the way to know is a blood test, starting with a full blood count.

How much iron does a woman need a day?

EFSA sets 16 mg a day for women who have periods, including pregnancy and breastfeeding, and 11 mg after menopause. The NHS uses 14.8 mg for women aged 19 to 49 and 8.7 mg from 50.

What helps the body absorb iron?

Vitamin C in the same meal, and some meat, fish or seafood, increase absorption of iron from plant foods (NIH). Tea, coffee, milk and phytic acid from wholegrains can lower it; the NHS advises people with iron deficiency anaemia to cut down on them.

Related entries and articles

• Lentils, white beans and chickpeas
• Spinach, tofu and pumpkin seeds
• Vitamin C, vitamin B12 and zinc
• Vegan diet: benefits and risks
• Recipe: bob chorba, Bulgarian white bean soup
• Recipe: warm lentil salad with roasted carrots and feta

Sources

1. NIH Office of Dietary Supplements: Iron, Fact Sheet for Health Professionals. ods.od.nih.gov
2. EFSA NDA Panel (2015). Scientific Opinion on Dietary Reference Values for iron. EFSA Journal 13(10):4254. efsa.europa.eu
3. EFSA NDA Panel (2024). Scientific opinion on the tolerable upper intake level for iron. EFSA Journal 22(6):8819. efsa.europa.eu
4. EFSA: Overview on Tolerable Upper Intake Levels as derived by the SCF and the EFSA NDA Panel, version 11 (2025). efsa.europa.eu
5. Commission Regulation (EU) No 432/2012 – permitted health claims. legislation.gov.uk
6. NHS: Vitamins and minerals – Iron. nhs.uk
7. NHS: Iron deficiency anaemia. nhs.uk
8. NIH Office of Dietary Supplements: Vitamin C, Fact Sheet for Consumers. ods.od.nih.gov
9. NIH Office of Dietary Supplements: Dietary Supplements – What You Need to Know. ods.od.nih.gov
10. USDA FoodData Central, SR Legacy records for the ten foods in the table (FDC IDs listed under it). fdc.nal.usda.gov

This page is for information only and is not medical or dietary advice.