Tolerable upper intake level (UL) for selected nutrients for adults

nutrient UL per day

calcium 2,500 milligrams

copper 10 milligrams

fluoride 10 milligrams

folic acid* 1,000 micrograms

iodine 1,100 micrograms

iron 45 milligrams

magnesium** 350 milligrams

manganese 11 milligrams

niacin* 35 milligrams

phosphorus 4 grams

selenium 400 micrograms

vitamin A*** 3,000 micrograms (10,000 IU)

vitamin B₆ 100 milligrams

vitamin C 2,000 milligrams

vitamin D 50 micrograms (2,000 IU)

vitamin E* 1,000 milligrams

zinc 40 milligrams

*The UL for vitamin E, niacin, and folic acid applies to synthetic forms obtained from supplements or fortified foods.

**The UL for magnesium represents intake from a pharmacological agent only and does not include food or supplements.

***As preformed vitamin A only (does not include beta-carotene).

Source: National Academy of Sciences, Dietary Reference Intakes (1997, 1998, 2000, 2001, and 2002).