Quick answer
Adults need 8 to 18 mg of iron a day from food and supplements, depending on age and sex, and 27 mg in pregnancy. The upper limit is 45 mg a day. Many iron-only tablets hold 65 mg, more than that limit, so check with a clinician before taking one every day.1,2
Key facts
- Men and women over 50 need 8 mg of iron a day; women aged 19 to 50 need 18 mg, the same as the Daily Value printed on labels.1,2
- Pregnancy raises the need to 27 mg a day.1
- Doses of 60 mg or more raise the hormone hepcidin, which lowers absorption of the next day's dose.3
- Infants aged 7 to 12 months need 11 mg a day, more than adult men.2
Recommended amounts by age
| Age or stage | Male | Female |
|---|---|---|
| 0 to 6 months | 0.27 mg | 0.27 mg |
| 7 to 12 months | 11 mg | 11 mg |
| 1 to 3 years | 7 mg | 7 mg |
| 4 to 8 years | 10 mg | 10 mg |
| 9 to 13 years | 8 mg | 8 mg |
| 14 to 18 years | 11 mg | 15 mg |
| 19 to 50 years | 8 mg | 18 mg |
| 51 years and older | 8 mg | 8 mg |
| Pregnancy, any age | 27 mg | |
| Breastfeeding, 18 or younger | 10 mg | |
| Breastfeeding, 19 and older | 9 mg |
The figure for babies up to 6 months is an adequate intake based on what healthy breastfed infants get, not a full recommended allowance. Teen girls need 15 mg against 11 mg for teen boys, and women go on needing more than men until 51.2
The upper limit
| Age or stage | Upper limit |
|---|---|
| Birth to 13 years | 40 mg |
| 14 years and older, including pregnancy and breastfeeding | 45 mg |
The limit was set at the intake linked to stomach and bowel side effects from iron salts. It is not a target. Doctors sometimes prescribe more for a while when stores need rebuilding, and that is their call to make, not a label's.2
What supplements contain
Multivitamins with iron, especially those made for women, typically provide 18 mg, 100% of the Daily Value. Iron-only supplements usually provide more, often 65 mg, which is 360% of the Daily Value.2
Forms carry different amounts of iron: ferrous fumarate is 33% iron by weight, ferrous sulfate 20% and ferrous gluconate 12%. The Supplement Facts panel lists the iron itself, so no arithmetic is needed.2
A 325 mg tablet of ferrous sulfate therefore holds about 65 mg of iron, because ferrous sulfate is one fifth iron by weight. The Supplement Facts panel already shows the 65 mg, so compare products by that figure rather than by tablet size.2
Why the body does not absorb it all
In young women with low iron stores, doses of 60 mg or more raised the hormone hepcidin for a day and cut absorption of the next day's dose by 35% to 45%. A sixfold larger dose, 240 mg instead of 40 mg, gave only about three times as much absorbed iron.3
That is why researchers have tested giving iron every other day instead of daily. The timing guide sets out what those trials found.4
Meat, seafood and poultry contain heme iron, which the body absorbs better than the nonheme iron in plants and fortified foods. In the US, about half of the iron people eat comes from bread, cereal and other grain foods.2
The body absorbs about 14% to 18% of the iron in mixed diets that include meat, seafood and vitamin C, and 5% to 12% of the iron in vegetarian diets.2
People who eat no meat, poultry or seafood need about 1.8 times the recommended amount, because the body absorbs the nonheme iron in plant foods less well than the heme iron in meat.1,2
Athletes and blood donors
People who exercise intensely might need 30% to 70% more iron than people who are moderately active or sedentary.5
Hard exercise can reduce iron absorption through the hormone hepcidin, and athletes also lose iron in sweat.5
Adults in the US may give blood as often as every 8 weeks, which can drain iron stores; about 25% to 35% of regular donors end up with low iron.2
In the one large trial of donors, 37.5 mg a day, about twice the Daily Value, brought hemoglobin back within about a month. That is a good deal less than the 65 mg in many iron-only tablets.2,6
When the amount is too high
Stomach and bowel side effects become more likely at 45 mg a day or more, and supplements with 25 mg or more can lower zinc absorption. Very large single amounts, above about 20 mg per kg of body weight, are dangerous, and children are most at risk from accidental overdose.2
Questions people ask
Is 65 mg of iron a day too much?
It is above the 45 mg upper limit for adults, so take it only on a clinician's advice. Doctors sometimes prescribe more than the limit for a while to rebuild low stores, and trials in donors and in women with low iron used 37.5 to 100 mg a day.2,6,7
How much iron does a vegetarian need?
About 1.8 times the usual amount: roughly 32 mg a day for a vegetarian woman aged 19 to 50 and about 14 mg for a vegetarian man, counting food and supplements.2
Should I take iron every day or every other day?
Both schedules have been tested in women with low iron stores. On alternate days each dose was absorbed better and caused fewer stomach complaints, while daily dosing reached the same ferritin in half the time. Ask your clinician which suits your situation.4,7
See what we make
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Sources
- Office of Dietary Supplements, National Institutes of Health. Iron: Fact Sheet for Consumers. Updated August 17, 2023. Opened 2026-10-07.
- Office of Dietary Supplements, National Institutes of Health. Iron: Fact Sheet for Health Professionals. Updated September 4, 2025. Opened 2026-10-07.
- Moretti D, Goede JS, Zeder C, et al. Oral iron supplements increase hepcidin and decrease iron absorption from daily or twice-daily doses in iron-depleted young women. Blood. 2015;126(17):1981-1989. Opened 2026-10-07.
- Stoffel NU, Cercamondi CI, Brittenham G, et al. Iron absorption from oral iron supplements given on consecutive versus alternate days and as single morning doses versus twice-daily split dosing in iron-depleted women: two open-label, randomised controlled trials. Lancet Haematol. 2017;4(11):e524-e533. Opened 2026-10-07.
- Office of Dietary Supplements, National Institutes of Health. Dietary Supplements for Exercise and Athletic Performance: Fact Sheet for Health Professionals. Updated April 1, 2024. Opened 2026-10-07.
- Kiss JE, Brambilla D, Glynn SA, et al. Oral iron supplementation after blood donation: a randomized clinical trial. JAMA. 2015;313(6):575-583. Opened 2026-10-07.
- von Siebenthal HK, Gessler S, Vallelian F, et al. Alternate day versus consecutive day oral iron supplementation in iron-depleted women: a randomized double-blind placebo-controlled study. EClinicalMedicine. 2023;65:102286. Opened 2026-10-07.
This page is information, not medical advice. Talk to your doctor or pharmacist about your own situation.