Vitamin D3 is available in 400, 800, 1000, 2000, 5000, 10,000, and 50,000 unit capsules. 50,000 IU (1.25 mg) capsules are available as a prescription. After that, a maintenance dose of 800 -C 2000 IU per day should be taken daily to maintain a vitamin D level above 30 ng/mL.read more >>