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The tolerable upper intake level (UL), or upper limit, for iodine is 1,100 mcg a day for adults 19 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 iodine from food, water and supplements together.
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Servings a day
This limit is the same for adults 19 and older, including pregnancy and breastfeeding.
Type the amount from your label to compare it with the upper limit.
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Iodine upper limits by age
| Age | Males | Females | Pregnancy | Breastfeeding |
|---|---|---|---|---|
| Birth to 6 months | Not set | Not set | – | – |
| 7-12 months | Not set | Not set | – | – |
| 1-3 years | 200 mcg | 200 mcg | – | – |
| 4-8 years | 300 mcg | 300 mcg | – | – |
| 9-13 years | 600 mcg | 600 mcg | – | – |
| 14-18 years | 900 mcg | 900 mcg | 900 mcg | 900 mcg |
| 19-30 years | 1,100 mcg | 1,100 mcg | 1,100 mcg | 1,100 mcg |
| 31-50 years | 1,100 mcg | 1,100 mcg | 1,100 mcg | 1,100 mcg |
| 51-70 years | 1,100 mcg | 1,100 mcg | – | – |
| 71+ years | 1,100 mcg | 1,100 mcg | – | – |
No upper limit could be set for babies; the National Academies say their intake should come from food and formula only.
How much Iodine you need
| Age | Males | Females | Pregnancy | Breastfeeding |
|---|---|---|---|---|
| Birth to 6 months | 110 mcg* | 110 mcg* | – | – |
| 7-12 months | 130 mcg* | 130 mcg* | – | – |
| 1-3 years | 90 mcg | 90 mcg | – | – |
| 4-8 years | 90 mcg | 90 mcg | – | – |
| 9-13 years | 120 mcg | 120 mcg | – | – |
| 14-18 years | 150 mcg | 150 mcg | 220 mcg | 290 mcg |
| 19-30 years | 150 mcg | 150 mcg | 220 mcg | 290 mcg |
| 31-50 years | 150 mcg | 150 mcg | 220 mcg | 290 mcg |
| 51-70 years | 150 mcg | 150 mcg | – | – |
| 71+ years | 150 mcg | 150 mcg | – | – |
* Adequate Intake (AI): the amount set when there isn’t enough evidence for an RDA.
What counts toward the Iodine limit
The limit counts iodine from food, water and supplements together.
What happens with too much Iodine
The National Academies based the adult UL for iodine on a rise in TSH (thyroid-stimulating hormone) above baseline, which the report calls "an indicator for increased risk of developing clinical hypothyroidism"; in two-week studies of adults given supplemental iodide (30 men in one, 9 men and 23 women in the other), TSH rose significantly in the groups given 1,500 µg/day or more, though in the study of men it stayed within the normal range. The report says high iodine intakes from food, water and supplements "have been associated with thyroiditis, goiter, hypothyroidism," hyperthyroidism, sensitivity reactions, thyroid papillary cancer and acute responses in some individuals. It found animal data of limited use in setting the UL, which rests on these human studies.
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 Iodine 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.