How Do You Convert 4,000 IU of Vitamin D to Milligrams?

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First, convert the 4,000 IU of vitamin D to micrograms by dividing 4,000 by 40 for a total of 100 micrograms, then convert micrograms to milligrams by dividing 100 by 1,000 for a total of 0.10 milligrams. The abbreviation IU stands for International Unit, and it is an internationally recognized method to measure vitamins, vaccines and other medications.