Question: 1 microgram is equal to how many iu?
Answer: 40 IU of vitamin D equals 1 µg, which can be converted to 0.001 mg. The RDA for an adult ranges from 600-800 IU. In micrograms, that would be 15 to 20 µg. Using milligrams changes the value range to 0.015-0.020 mg.