How much iron you actually need per day
The RDA is 8 mg a day for men but 18 mg for premenopausal women, one of the biggest sex differences in nutrition. The numbers, why heme and non-heme iron differ, why vitamin C helps, and why you should not supplement without testing.
What people ask us next.
- How much iron do I need a day?
- The RDA is 8 mg a day for adult men and postmenopausal women, but 18 mg for women aged 19 to 50 because of menstrual losses, and 27 mg during pregnancy (NIH ODS). Vegetarians and vegans need roughly 1.8 times these amounts because plant iron is absorbed less efficiently. This is one of the largest sex- and life-stage differences in nutrition, which is why iron advice depends so heavily on who you are rather than a single universal figure.
- Why do women need more iron than men?
- Because menstruation causes regular iron losses. Women aged 19 to 50 need 18 mg a day, more than double the 8 mg for men, to replace the iron lost through menstrual bleeding, and the requirement rises to 27 mg in pregnancy to support the expanding blood volume and the growing fetus (NIH ODS). After menopause, when menstrual losses stop, women's requirement drops to the same 8 mg as men. This is why iron deficiency is concentrated in menstruating and pregnant women.
- What is the difference between heme and non-heme iron?
- Heme iron comes from animal sources, meat, poultry, and fish, and is absorbed efficiently and consistently, while non-heme iron comes from plants, eggs, and fortified foods and is absorbed much less well, with its uptake heavily influenced by other foods in the meal (NIH ODS). This is why the same milligram amount means very different things depending on the source, and why vegetarians, relying on non-heme iron, need to aim higher and pair it with vitamin C.
- Does vitamin C help iron absorption?
- Yes, markedly, for non-heme iron. Having a source of vitamin C, citrus, peppers, tomatoes, or strawberries, in the same meal as plant iron significantly increases how much is absorbed (NIH ODS). Conversely, the tannins in tea and coffee, calcium, and the phytates in whole grains and legumes reduce non-heme iron absorption. For anyone relying on plant iron, pairing it with vitamin C and separating iron-rich meals from tea or coffee are among the most effective steps.
- Should I take an iron supplement?
- Only if a blood test confirms you are deficient, ideally under medical guidance. Iron is a nutrient where excess is genuinely harmful: the body cannot easily excrete a surplus, high intake causes gastrointestinal side effects, and in people with hemochromatosis iron overload damages organs (NIH ODS). The upper limit is 45 mg a day. Taking iron just in case is a real risk, not a harmless habit, so unlike some nutrients, iron should never be supplemented routinely without confirming a need.
Every claim, cited.
The Larderlab Team builds evidence-led frameworks for eating, lifting, and stocking a kitchen. We cite every claim. We publish the spreadsheet when possible. We buy what we review at retail price. When new data lands, we revise with a dated note.
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