IU stands for International Units and is used for the measurement of drugs and vitamins. As IU is a measurement of the amount of minerals and vitamins present in a tablet or capsule, it is essential to know how much of IU is enough and also how to convert this unit into other units such as mgs and mcgs.

U (international unit):

An International Unit (IU) is an internationally accepted amount of a substance. This type of measure is used for the fat-soluble vitamins (such as vitamins A, D and E) and certain hormones, enzymes, and biological (such as vaccines).

The definition of an international unit (IU) is generally arbitrary, technical, and eminently forgettable. For example, an IU of vitamin E is the specific biological activity of 0.671 milligrams of d-alpha-tocopherol. Nonetheless, most IUs are quite handy and helpful in use as a means of standardizing measures.

The International Conference officially defines all international units for Unification of Formulae.

IU in vitamins:

Some vitamins specifically A, E and D are expressed as a unit of biological activity (IU, International Units), rather than as weight such as grams, milligrams or micrograms. Occasionally, it is helpful to know the weight of a nutrient expressed this way.

International units exist in order to account for the fact that certain preparations of the same vitamin are not bioequivalent. Regardless of the preparation 1 IU will provide the same biological activity. For instance, 1 IU Vitamin E equals the biological equivalent of about 0.667 mg d-alpha-tocopherol, or of 1 mg of dl-alpha-tocopherol acetate. Though the mass of each preparation is different, the biological activity is the same.

In Vitamin E:

1 IU of vitamin E is equivalent to 0.66 milligrams of delta-alpha-tocopherol or 1 milligram of alpha-tocopherol acetate. Alpha-tocopherol vitamin E is the one with the most bioavailability in humans and you need 22.4 IU of this form of vitamin E daily.

In Vitamin D:

1 IU, of vitamin D can be converted to .025 micrograms of vitamin D in the form of cholecalciferol. Vitamin D is important; it helps to keep your bones strong by aiding in the absorption of calcium. You need 600 IU of vitamin D as an adult, but after the age of 70 it increases to 800 IU.

In Vitamin A:

Vitamin A makes up a group of compounds that play a role in reproduction, vision, bone growth and cell division. Carotenoids, beta-carotene, retinol, alpha-carotene and lutein are just a few of the compounds related to vitamin A.

Your body absorbs vitamin A in the form of retinol most efficiently. Animal foods, such as beef liver, milk and eggs provide this form of vitamin A. IU of vitamin A is equal to 0.3 mcg of retinol or 0.6 mcg of beta-carotene.

Difference between IU and MCG?

Basically, Mg is mass and IU is effect. There is a difference between them on the basis of what they set out to measure.

Milligrams (mg) are a measure of mass (or weight, which on planet Earth is roughly the same thing.) A milligram is one thousandth of a gram.

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

There are, for example, 22 IU of insulin is equivalent to 1 milligram of dry, pure, crystalline insulin.

IU for example is used for fat-soluble vitamins.
mcgs are used to measure very, very tiny amounts of other vitamins.
(Bear in mind that vitamins are very, very powerful chemicals – you only need small
amounts of some)

Mcg is a microgram – that is 1/1000 of a milligram.
You are probably familiar with the milligram but don’t know it.
Many products are labeled in both ounces and milligrams.
There are about 28 mg’s in an ounce.

How to convert IU to MCG?
The contents of three ingredients (Vitamin A, D, and E) are expressed as International Units (IU) on dietary supplement and food labels. Guidelines for converting units of IU to mg are given below.
For these calculations, the formulas are:

  • To convert Vitamin A as retinol:
    From IU to mcg: IU * 0.3 = mcg
    For example: 5000 IU * 0.3 = 1500 mcg
    From mcg to IU: mcg / 0.3 = IU
  • To convert Vitamin A as beta-carotene:
    From IU to mcg: IU * 0.6 = mcg
    For example: 5000 IU * 0.6 = 3000 mcg
    From mcg to IU: mcg / 0.6 = IU
  • To convert Vitamin D:
    From IU to mcg: IU * 0.025 = mcg
    For example: 400 IU * 0.025 = 10 mcg
    From mcg to IU: mcg / 0.025 =IU
  • To convert Vitamin E if the product label has DL-Alpha-tocopherol as the ingredient:
    From IU to mg: IU * 0.9 = mg
    For example: 30 IU * 0.9 = 27 mg
    From mg to IU: mg / 0.9 = IU
  • To convert Vitamin E if the product label has D-Alpha-tocopherol as the ingredient:
    From IU to mg: IU * 0.67 = mg.
    For example: 30 IU * 0.67 = 20.1 mg
    From mg to IU: mg / 0.67 = IU

IU is thus significant in order to find out about the content of minerals and vitamins present in tablets, supplements and basic diet. In order to live a healthy and nutritious life it is very important for us to have a detailed knowledge as to what IU really is and how much of it is sufficient.

About The Author

Hina Khan is a devout herbal tea fan and serves as the Business Development Manager at Buddha’s Herbs. She’s a nature enthusiast and passionate about writing on natural products. During her time at Buddha’s Herbs she’s developed great insight on natural remedies and how different products work for different ailments. On the forum, she’ll be there to help guide you on Buddha’s Herbs range of products.