IU
International Unit — a legacy potency measure for vitamins A, D, and E.
IU (International Unit) is a non-metric potency unit defined per-vitamin. The conversions you'll see most:
- Vitamin D3: 1 mcg = 40 IU. So 2000 IU = 50 mcg.
- Vitamin E (d-alpha): 1 mg = 1.49 IU.
- Vitamin A (retinol): 1 mcg RAE = 3.33 IU.
EU labels are migrating to mcg (micrograms). When comparing US-shipped products to EU labels, do the conversion before judging dose adequacy.