“RDA” stands for “recommended dietary allowance.”
In the United States, for an adult with, or under, 70 years of age, the recommended dietary allowance (RDA) for vitamin D is 600 IU. If you are over 70, the RDA for vitamin D is set at 800 IU. (1)
However, if you look at a bottle of a bestselling vitamin D supplement, you’ll most likely find a much larger number like 5,000 or 10,000 IU.