I reccommend between 5000 ie to 10,000 ie, read below and at the cited site for reliable data on it. See under 'Research' and browse several of the studies cited under a few of the conditions related to the research for an idea of how much is being used in studies.
about reccommended dose
"Caucasian skin produces approximately 10,000 IU vitamin D in response to 20–30 minutes summer sun exposure—50 times more than the US government's recommendation of 200 IU per day!This high rate of natural production of vitamin D3 cholecalciferol (pronounced koh·luh·kal·sif·uh·rawl) in the skin is the single most important fact every person should know about vitamin D—a fact that has profound implications for the natural human condition.VIDEO: 15 year old Ryan McLaughlin (Shine on Scotland) wins award for his campaign for free vitamin D to prevent MS Technically not a "vitamin," vitamin D is in a class by itself. Its metabolic product, calcitriol, is actually a secosteroid hormone that is the key that unlocks binding sites on the human genome. The human genome contains more than 2,700 binding sites for calcitriol; those binding sites are near genes involved in virtually every known major disease of humans.
"If well adults and adolescents regularly avoid sunlight exposure, research indicates a necessity to supplement with at least 5,000 units (IU) of vitamin D daily."
"In 1999, Vieth indirectly asked the medical community to produce any evidence 10,000 units of vitamin D a day was toxic, saying "Throughout my preparation of this review, I was amazed at the lack of evidence supporting statements about the toxicity of moderate doses of vitamin D." He added: "If there is published evidence of toxicity in adults from an intake of 250 ug (10,000 IU) per day, and that is verified by the 25(OH)D concentration, I have yet to find it."
Like most medication, cholecalciferol is certainly toxic in excess, and, like Coumadin, is used as a rodent poison for this purpose. Animal data indicates signs of toxicity can occur with ingestion of 0.5 mg/kg (20,000 IU/kg ), while the oral LD50 (the dose it takes to kill half the animals) for cholecalciferol in dogs is about 88 mg/kg, or 3,520,000 IU/kg. This would be equivalent to a 110-pound adult taking 176,000,000 IU or 440,000 of the 400 unit cholecalciferol capsules.