Question

How can I convert from international units (IU) to milligrams or micrograms?

Answer 1

It varies from one substance from another.

The international unit is based on the activity or effect of biologically active substances. Here are some examples.

• Vitamin A: 1 IU is the biological equivalent of 0.3 μg of retinol or
  of 0.6 μg of beta-carotene.

• Vitamin C: 1 IU corresponds to 50 μg of L-ascorbic acid

• Vitamin D: 1 IU is the biological equivalent of 0.025 μg of
  cholecalciferol.

• Vitamin E: 1 IU is the biological equivalent of ²/₃ mg of
  d-alpha-tocopherol or 0.9 mg of dl-alpha-tocopheryl acetate.

• Insulin: 1 IU is equivalent to 0.0347 mg of human insulin.

For other substances, you may have to consult a pharmacist.

EXAMPLE

The recommended dietary allowance (RDA) of Vitamin D is 600 IU. What mass of Vitamin D does this represent?

Solution

Mass of Vitamin D = 600 IU × `(0.025"µg")/(1"IU")` = 15 µg