Supplement Facts Generator

Converting IU to mcg and mg for vitamins A, D and E

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US labels now declare vitamins A, D and E by weight: vitamin A in mcg RAE, vitamin D in mcg and vitamin E in mg (alpha-tocopherol). Supplier specifications still often use International Units (IU). An IU measures biological activity, so the conversion depends on the nutrient and its chemical form.

Factors (FDA guidance, August 2019)

Nutrient and form 1 IU equals
Vitamin D (D2 or D3) 0.025 mcg
Vitamin A, retinol (preformed) 0.3 mcg RAE
Vitamin A, supplemental beta-carotene 0.3 mcg RAE
Vitamin A, dietary beta-carotene 0.05 mcg RAE
Vitamin A, alpha-carotene 0.025 mcg RAE
Vitamin E, natural (RRR-/d-alpha-tocopherol) 0.67 mg
Vitamin E, synthetic (all-rac-/dl-alpha-tocopherol) 0.45 mg

Worked examples

  • Vitamin D3 1,000 IU × 0.025 = 25 mcg, which is 125% of the 20 mcg Daily Value.
  • Vitamin E as dl-alpha-tocopheryl acetate, 30 IU × 0.45 = 13.5 mg, which is 90% of 15 mg.
  • Vitamin A as retinyl palmitate, 5,000 IU × 0.3 = 1,500 mcg RAE, which is 167% of 900 mcg.

Showing IU on the label

For vitamin D, the IU amount may be shown in parentheses after the mcg amount, for example “25 mcg (1,000 IU)” (21 CFR 101.36(b)(2)(ii)(B)). The generator has an option for this.

Why there is no generic IU to mg converter

There is no universal factor. A converter that offers one for any nutrient will give wrong answers, so our unit converter only converts the nutrients and forms listed above.

Sources

  1. Guidance for Industry: Converting Units of Measure for Folate, Niacin, and Vitamins A, D, and E on the Nutrition and Supplement Facts Labels — U.S. Food and Drug Administration (FDA guidance)
  2. Nutrition labeling of dietary supplements — U.S. Food and Drug Administration (21 CFR 101.36)