Iron: what it does and how much you need
Iron helps make haemoglobin, the protein in red blood cells that carries oxygen around the body. Adults need 8 milligrams for men, 18 milligrams for women aged 19 to 50, and 8 milligrams for women over 50, and the upper limit is 45 milligrams a day.
General information, not medical advice. Check with a doctor or pharmacist before taking a supplement, especially if you are pregnant or breastfeeding, take any medicine, or are under 18.
In the UK
In the UK, adults need 8.7 milligrams a day for men and women over 50, and 14.8 milligrams for women aged 19 to 49, and the NHS says up to 17 milligrams a day from supplements is unlikely to cause harm, unless a doctor has prescribed more.
How much you need and the upper limit
| US (NIH) | UK (NHS) | |
|---|---|---|
| Adults need | 8 milligrams for men, 18 milligrams for women aged 19 to 50, and 8 milligrams for women over 50 | 8.7 milligrams a day for men and women over 50, and 14.8 milligrams for women aged 19 to 49 |
| Upper limit | 45 milligrams a day | Up to 17 milligrams a day from supplements |
The UK figure is the amount the NHS says is unlikely to cause harm. Figures are for adults.
Cautions
- Keep iron supplements well away from children: an accidental overdose is dangerous for them.
Food sources
- Lean meat
- Seafood
- Poultry
- Beans and lentils
- Spinach
- Fortified cereals
- Raisins
Forms on the label
- Ferrous sulfate is the most common and cheapest iron form, and it can upset the stomach for some people.
- Iron bisglycinate is iron bound to glycine, often chosen because it tends to cause less stomach upset than ferrous sulfate.
Dose questions
Quick answers
- What does iron do?
- Iron helps make haemoglobin, the protein in red blood cells that carries oxygen around the body.
- How much iron do adults need?
- Adults need 8 milligrams for men, 18 milligrams for women aged 19 to 50, and 8 milligrams for women over 50 (US, NIH). In the UK: 8.7 milligrams a day for men and women over 50, and 14.8 milligrams for women aged 19 to 49 (NHS).
- What is the upper limit for iron?
- US: 45 milligrams a day. UK (NHS): up to 17 milligrams a day from supplements is unlikely to cause harm.
- Which foods have iron?
- Lean meat, seafood, poultry, beans and lentils, spinach, fortified cereals, raisins.
- What should I watch out for with iron?
- Keep iron supplements well away from children: an accidental overdose is dangerous for them.
Sources
- NIH Office of Dietary Supplements fact sheet
https://ods.od.nih.gov/factsheets/Iron-HealthProfessional/ - NHS vitamins and minerals guidance
https://www.nhs.uk/conditions/vitamins-and-minerals/iron/
Ask Supplement Check yourself
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In Claude or any app that takes MCP connectors, add https://goodturn-mcp.pages.dev/supplementcheck/mcp and ask: “Is 65 mg of iron too much?”