.I grew up in Honolulu and don't seem to be very good at converting sunlight to vitamin D. I take 6000 international units once a day and 50,000 prescription units once a week. That is gotten my blood level to 32 but they just tested it and we may up it. If you're buying vitamin D retail make sure it is USP, which is a purity standard. It needs to be a gel cap. Hope that helps. I would start by knowing what your blood level is now