In May 2016, the U.S. Food and Drug Administration (FDA) announced regulations that required changes to the Supplement Facts label related to the use of units of measure and their conversions. The new regulations were mandatory starting in 2020-2021. For more information from the FDA, please click here. For specific guidance on unit conversions, please click here. The application of DSID results may require the use of the older units of measure or a conversion of the older units to the new units. The table below shows the changes in the units of measure, where applicable.
| Nutrient | New DV Unit | Conversion | Older DV Unit* |
| Vitamin A | μg RAE |
1 IU retinol = 0.3 mcg RAE 1 IU supplemental beta-carotene = 0.3 mcg RAE |
IU** |
| Vitamin E | mg alpha-tocopherol |
1 IU (natural) = 0.67 mg Vitamin E (as alpha-tocopherol) 1 IU (synthetic) = 0.45 mg Vitamin E (as alpha-tocopherol) |
IU** |
| Vitamin D | μg | 1 IU = 0.025 μg | IU |
| Folate | μg DFE |
1 μg DFE = 1 μg folates 1 μg DFE = 0.6 μg folic acid |
μg |
| Niacin | mg NE |
1 mg NE = 1 mg niacinamide 1 mg NE = 1 mg inositol hexanicotinate 1 mg NE = 1 mg niacin 1 mg NE = 60 mg tryptophan |
mg |
*The data in the DSID-4 are reported using the older DV units. These will be updated in DSID-5 and the data will be provided for both the older and new units of measure.
**Additional information about these older DV units and about how to apply information from the labels of dietary supplements are listed below for each nutrient.
Vitamin A in the diet can come in different forms: retinol, beta-carotene, alpha-carotene, and beta-cryptoxanthin. Some of these forms have greater bioavailability than others. Vitamin A has previously been reported in international units (IU). New FDA labeling guidelines require reporting of vitamin A in the unit, RAE (retinol activity equivalent) in order to account for the differing bioavailability of the forms. Vitamin A in µg RAE can only be directly converted into IUs if the sources of vitamin A are known. 1 µg RAE = 1 µg retinol and 1 µg RAE = 2 µg supplemental beta-carotene.
New FDA guidelines require that Vitamin E content be determined based on the source of vitamin E and that it be reported as mg alpha-tocopherol rather than in IU. Vitamin E in food and dietary supplements can come from natural or synthetic forms.. Naturally sourced vitamin E is called RRR-alpha-tocopherol (commonly listed on dietary supplement labels as d-alpha-tocopherol); the synthetically produced form is all rac-alpha-tocopherol (commonly listed on dietary supplement labels as dl-alpha-tocopherol). One mg vitamin E (alpha-tocopherol) (as displayed on the labels) is equivalent to 1 mg RRR-alpha-tocopherol or 2 mg all rac-alpha-tocopherol.
New FDA guidelines require that vitamin D be reported in µg. Manufacturers may also list the IU amount in parentheses following the amount in µg.
Dietary folate can come in different forms: naturally occurring folates and synthetic folic acid. Previously all folates and folic acid were reported as µg folic acid. New FDA guidelines require that folates/folic acid be reported in Dietary Folate Equivalents (DFE) with µg of folic acid in parentheses. Folic acid has greater bioavailability than naturally occurring folates.
New FDA guidelines require that niacin be reported as Niacin Equivalents (NE). Dietary niacin can come in several forms, and the new unit accounts for tryptophan as a source of niacin.