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Ingredients and Dosages
January 1999

The most important information on the label is the name of the dietary supplement(s) or the product name. This indicates the key substances contained within. However, these terms may be ambiguous. For more information about what the name of a supplement may mean, see standard terminology.

FDA regulations require that the label contain a list of the specific ingredients contained in the product. Recommended daily nutrition intakes for some of these ingredients must also be listed.

Dosage units

Dosage units may be listed as

  • liquid volume (ml or milliliters, cc for cubic centimeters)
  • dry weight (kg or kilograms, mg or milligrams, g or grams)
  • or by biological assay (International Units)

An international unit (I.U.) is a standard unit of measurement of biological activity that is used for fat soluble vitamins (A, D and E) as well as for some hormones, enzymes, and vaccines. It is an internationally-recognized standard established by the International Conference for Unification of Formulae. One I.U. represents a different amount for different substances. The weight equivalents for fat soluble vitamins are as follows:

Beta Carotene
(Vitamin A)
1 mg = 833 IU
Vitamin D 2.5 mcg = 100 IU
Vitamin E 1 mg = 1 IU

Dosage amounts

The actual dosage amount in a dietary supplement product may be different from the labeled amount. This is because high levels of accuracy are costly to achieve and because the added benefits of such accuracy are not believed to be worth the higher prices that would result.

Every substance disintegrates, or becomes less potent, with time. Manufacturers sometimes intentionally make substances more potent than labeled in order to compensate for their disintegration and to give the product a longer shelf life. This is called building in an overage. Both the disintegration rate and the overage built in to offset disintegration can cause further variances between a product's actual and labeled dosage amounts.

Disintegration can be accelerated by improper storage conditions such as exposure to light, heat, moisture, or air. Supplements that are not properly stored may lose potency faster than the expiration date indicates they should.

Overages are based on the rate that a particular substance disintegrates and on the degree to which a variance in its dosage can be tolerated. They are set low enough to avoid any risk of overdose, and kept high enough to extend the product's shelf life as much as possible.

For example, if a substance labeled to contain 200 mg. per capsule has an allowable variance of 10%, each capsule should contain no less than 180 mg. and no more than 220 mg. up until the labeled expiration date assuming the product was properly stored.



More about reading the label:

New labeling rules in effect

Health benefit claims

Ingredients and recommended dosages

Dosage units

Dosage amounts

Expiration date

Lot number

Dissolution and bioavailability

Certification claims

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(c) Copyright 1999-2003 Dietary Supplement Quality Initiative. For permission to reprint, please contact our editor.