Supplement labels use several unit systems at once. Most minerals and B vitamins are given by mass: milligrams (mg) or micrograms (mcg, sometimes written µg). A few nutrients carry activity units that account for different chemical forms.
International Units
Vitamin D is the common case. 1 mcg of vitamin D equals 40 IU, so 25 mcg is 1,000 IU. US labels since 2020 must print micrograms and may add IU in brackets. Dosescope records what the label prints in the unit it prints; when a label gives both, the mcg figure is stored and the IU figure is noted in the form column.
DFE, RAE and NE
- mcg DFE (dietary folate equivalents): folic acid from supplements counts 1.7 times as much as food folate, so 400 mcg of folic acid is printed as 680 mcg DFE.
- mcg RAE (retinol activity equivalents): vitamin A from beta-carotene counts less than preformed retinol.
- mg NE (niacin equivalents): niacin plus a contribution from tryptophan.
Two labels can therefore print different numbers for the same amount of the same compound, depending on which convention they follow. That is why comparison rows keep the unit next to every number and never hide a row whose units differ.