Supplement measurements

An HSI member named Allie would like some help figuring out the measurements she finds on supplement bottles and in the e-Alert. Allie writes:

“What is an IU; an MG, an MCG? Are there mgs in a mcg; mcgs in an mg? What is the relationship to IU’s? I find it impossible to compare one supplement with another because I don’t know what these abbreviations stand for. Articles talk about one should take so many milligrams a day of something (vitamin C, for instance) for good health, but one bottle has vitamin C — so many mcgs; another has vitamin C — so many mgs. Please help!”

Most of your question is easy to answer, Allie (although things get a bit sticky with the IUs). Here’s a quick rundown:
* g = gram, which is 1/1000 of a kilogram (kg)
* mg = milligram, which is 0.001 of a gram, and 1000 micrograms
* mcg = micrograms, which is 0.001 of a milligram, and one millionth of a gram

IUs are international units, and they don’t fit neatly into the metric system of mass that uses the kilogram as the base unit. For each substance that’s measured in IUs, there’s an international agreement that specifies the expected biological effect that will occur with a dose of 1 IU. For instance, 1 IU of vitamin C is equal to 50mcg (although you’ll almost always see vitamin C dosage in either mgs or gs). 1 IU of vitamin E (which I’ve never seen in any measurement other than IUs) is equal to 2/3 mg.

Most of the vitamins you’ll find in supplements are measured in mg and mcg.

And that’s about the size of it.

To Your Good Health,

Jenny Thompson
Health Sciences Institute