Generally, international units are used to measure vitamins" such as A, C, E, D, etc...and not used for minerals" such as iron. 1 IU vitamin A = 0.3 mcg (micrograms) 1 IU vitamin D = 0.025 mcg 1 IU vitamin E = 0.7 mcg as d-alpha tocopherol The translation from IU to micograms or milligrams is different for every vitamin; and as far as I know there is no converting measurement for Iron to go from