Vitamin Measurements

What's the difference between mg, mcg and IUs?

The units of measure for supplements can be confusing. Mg and mcg refer to the metric system units of milligram and microgram respectively. A milligram is 1/1000 of a gram (which is about a ¼ of a teaspoon), whereas a microgram is 1/1000 of a milligram (ie: 1/1,000,000 of a gram - one millionth). Definitely look for the unit when comparing supplement products, as it can make a big difference.

IU refers to International Units, which was the standard measure up until 1980 and is still used to label some supplement products (especially vitamins A, D, and E and some enzymes). This unit is essentially an arbitrary internationally accepted and recommended amount that changes from substance to substance. It has no absolute value in weight.

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