Concept and Difference Between mg & IU

What is an International unit?

An international unit (IU) is a unit of measurement for the amount of a substance; the mass or volume that constitutes one international unit varies based on which substance is being measured, and the variance is based on the biological activity or effect, for the purpose of easier comparison across substances. 

What is Milligram?

Milligrams (mg) is a measure of mass (weight). A milligram is one-thousandth of a gram.

What is the difference between mg and IU?

International Units (IU) is a measure based on the biological activity of a substance in the body. These units are arbitrarily set by a committee of researchers commissioned by the World Health Organization. The goal is to provide a measure of the effect on the body a substance will have regardless of its mass.

For Ex: 1 IU of Vitamin C is 50 mgs, but 1 IU of insulin is 0.045 milligrams. That's for the pure crystalline versions of those chemicals: a different preparation or a related chemical may have the same effect using a different amount, and that would also be 1 IU.

International units are used to quantify vitamins, hormones, medicines, vaccines, blood products, and similar biologically active substances.

How to Convert Between IU & MG and MCG

Milligrams and Micrograms

• The organization of the metric system makes conversion between units convenient by multiplying or dividing by multiples of 10. 
• On the metric scale of prefixes, milli- equals 1/1000 and micro- equals 1/1,000,000. 
• If the unit is grams, which measures the mass of a substance, then one gram contains 1,000 milligrams or 1,000,000 micrograms. 
• To convert from milligrams to micrograms, multiply by 1,000. 
• To convert from micrograms to milligrams, divide by 1,000. For example, 100 mg of vitamin C equals 100,000 mcg or µg.

ALSO READ: Difference between Assay and Purity

International Units

• Milligrams and micrograms indicate the amount of mass in a sample, but international units indicate the level of biological activity of a substance. One international unit, or IU, is a measurement of the biological effect that a specific substance has on the body. 
• An international agreement among various scientific organizations determined the IU value for specific formulations of vitamins. 
• For each type of vitamin preparation, there is a unique IU value based on the method used for formulating that vitamin.

ALSO READ: Difference Between Assay and Potency