Vitamin Conversions – International Units (IU) to mg or mcg

When you look at a food label, you might be confused at the variety of different measurements used to indicate how much of each vitamin is in that food. You’ll find terms like mg, mcg, IU and more. Why are there a variety of different terms used, and how do you convert between these different units?

International Units (IU) are one of the standardized units used to calculate or measure vitamin potency and biological effectiveness. IUs are preferred rather than weight for many vitamins, because different vitamin forms can have different levels of potency. IUs provide a standardized way to calculate a vitamin’s potency across different vitamin forms.

IU, mcg, and Other Label Unit Abbreviations

IU = international unit

RAE = retinal activity equivalents

DFE = dietary folate equivalent

NE = niacin equivalent

mg = milligram

mcg = μg = microgram

Vitamin Unit Conversions and Calculations

The information below provides an approximate vitamin conversion from standardized units (IU, RAE, DFE, NE) to milligrams or micrograms.

Vitamin A

1 IU = 0.3 mcg retinol

1 mcg RAE = 1 mcg retinol

1 mcg RAE = 2 mcg supplemental beta-carotene

1 mcg RAE = 12 mcg beta-carotene

1 mcg RAE = 24 mcg alpha-carotene

1 mcg RAE = 24 mcg beta-cryptoxanthin

Vitamin B


1 mcg DFE = 1 mcg food folate

1 mcg DFE = 0.6 mcg folic acid


1 mg NE = 1 mg niacinamide

1 mg NE = 1 mg inositol hexanicotinate

1 mg NE = 1 mg niacin

1 mg NE = 60 mg tryptophan

Vitamin D

1 IU = 0.025 mcg ergocalciferol (Vitamin D2)

1 IU = 0.025 mcg cholecalciferol (Vitamin D3)

Vitamin E

1 IU = 0.67 mg d-alpha tocopherol (natural)

1 IU = 0.45 mg dl-alpha tocopheryl (synthetic)

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