What Is the Conversion Rate of Iu to Mg?
There is no constant conversion rate between IU, or International Units, and mg, or milligrams. International Units are summary units designed to express the total amount of a vitamin present in a supplement, even if that vitamin is present in various forms, with various concentrations.
The value of one IU for a particular substance is set by international agreement. For example, one IU of vitamin A is equal to either .0003 mg of retinol, or .0006 mg of beta-carotene, according to the NIH. A supplement containing .00015 mg of retinol and .0003 mg of beta-carotene, then, would contain one IU of vitamin A. The FAQ section of the National Institutes of Health's website contains a conversion table for some common types of vitamins.