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The tolerable upper intake level (UL), or upper limit, for iron is 45 mg a day for everyone 14 and older. That is the most a day that is unlikely to cause harm for almost everyone; above it, the chance of side effects goes up. It is a ceiling, not a target. The limit counts iron from food, water and supplements together.
Check your amount
Servings a day
This limit is the same for everyone 14 and older, including pregnancy and breastfeeding.
Type the amount from your label to compare it with the upper limit.
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Iron upper limits by age
| Age | Males | Females | Pregnancy | Breastfeeding |
|---|---|---|---|---|
| Birth to 6 months | 40 mg | 40 mg | – | – |
| 7-12 months | 40 mg | 40 mg | – | – |
| 1-3 years | 40 mg | 40 mg | – | – |
| 4-8 years | 40 mg | 40 mg | – | – |
| 9-13 years | 40 mg | 40 mg | – | – |
| 14-18 years | 45 mg | 45 mg | 45 mg | 45 mg |
| 19-30 years | 45 mg | 45 mg | 45 mg | 45 mg |
| 31-50 years | 45 mg | 45 mg | 45 mg | 45 mg |
| 51-70 years | 45 mg | 45 mg | – | – |
| 71+ years | 45 mg | 45 mg | – | – |
How much Iron you need
| Age | Males | Females | Pregnancy | Breastfeeding |
|---|---|---|---|---|
| Birth to 6 months | 0.3 mg* | 0.3 mg* | – | – |
| 7-12 months | 11 mg | 11 mg | – | – |
| 1-3 years | 7 mg | 7 mg | – | – |
| 4-8 years | 10 mg | 10 mg | – | – |
| 9-13 years | 8 mg | 8 mg | – | – |
| 14-18 years | 11 mg | 15 mg | 27 mg | 10 mg |
| 19-30 years | 8 mg | 18 mg | 27 mg | 9 mg |
| 31-50 years | 8 mg | 18 mg | 27 mg | 9 mg |
| 51-70 years | 8 mg | 8 mg | – | – |
| 71+ years | 8 mg | 8 mg | – | – |
* Adequate Intake (AI): the amount set when there isn’t enough evidence for an RDA.
What counts toward the Iron limit
The limit counts iron from food, water and supplements together.
What happens with too much Iron
The National Academies based the adult UL for iron on gastrointestinal side effects: the report says high-dose iron supplements are "commonly associated with constipation and other gastrointestinal (GI) effects including nausea, vomiting, and diarrhea," seen mainly in people who took high levels of supplemental iron on an empty stomach, and it took the lowest dose with these effects from a controlled, double-blind study of 97 Swedish adults. The report also describes acute toxicity from overdoses of medicinal iron, especially in young children, and says large doses of iron supplements may inhibit zinc absorption when both are taken in the fasting state. It calls the relationship between iron intake and both vascular disease and cancer "unclear at the present time," and notes that people with hereditary hemochromatosis or other iron-loading disorders may not be protected by the UL.
Sources: National Academies, Dietary Reference Intakes for Vitamin A, Vitamin K, Arsenic, Boron, Chromium, Copper, Iodine, Iron, Manganese, Molybdenum, Nickel, Silicon, Vanadium, and Zinc (2001); Health Canada, Dietary Reference Intakes tables (the joint U.S.-Canada values). Limits checked November 8, 2026. More from the NIH: Office of Dietary Supplements Iron fact sheet.
If you think you or a child took too much of a supplement, call Poison Control at 1-800-222-1222 (U.S., free, 24 hours) or use poison.org. In an emergency, call 911.
General information, not medical advice. Your doctor may recommend a different amount, for example to treat a deficiency. Talk to your doctor or pharmacist before you start, stop or change a supplement, especially if you are pregnant, nursing, take medication or have a medical condition.