how many iu in a mcg?
 Vitamin A: 1 IU is the biological equivalent of 0.3 mcg retinol, or of 0.6 mcg beta-carotene. Vitamin D: 1 IU is the biological equivalent of 0.025 mcg cholecalciferol or ergocalciferol. Vitamin E: 1 IU is the biological equivalent of 0.67 mg d-alpha-tocopherol, or 0.9 mg of dl-alpha-tocopherol. 