High quality vitamin D does not need to be licenced, although companies have realised that they can make a lot of money by licencing this food supplement, and asking doctors to prescribe it. The most cost effective form of vitamin D is available over the counter and compliance is best served by using 20,000 units of vitamin D weekly. The conversion factor is 40 units per microgram, so that 400 units=10 micrograms and 1000 units=25mcg. The recommended daily allowance (RDA) is 400 units daily. A very much higher dose of 10000 units daily has been shown to not be toxic.
(Heaney et al Am J Clin Nutr 77:204-10 2003).
Anxiety about toxicity only occurs with multivitamins that include vitamin A, and we are here talking about pure vitamin D. If we assume that 3000 units daily or 20,000 units weekly is a generally useful and safe dose, then we might be suggesting an annual dose of 1 million units. We are here comparing costs. There is no evidence that licenced preparations should be used and we therefore do NOT recommend the use of licenced products. Doctors CAN prescribe Bio Vitamin D3 20,000 units weekly.