How Many Milligrams Are There in 1,000 IU of Vitamin D-3?

A 1,000 international unit dose of vitamin D is 25 micrograms, which converts to approximately 0.03 milligrams, according to Mayo Clinic. As of 2010, the recommended daily allowance of vitamin D is 600 international units for people ages 1 to 70 years or for women who are pregnant or breast-feeding.