A challenge for public health is to make recommendations for the intake of vitamin D to optimize health and prevent disease. This can be accomplished by the use of vitamin D supplements from plant sources (vitamin D2), from mammalian sources (D3), or as a prehormone (25 hydroxyvitamin D, 25OHD). While these three sources are generally effective for raising and maintaining vitamin D status, they are not equivalent. There are meaningful differences in their routes of absorption and metabolism, including their use for production of the vitamin D hormone 1,25 dihydroxyvitamin D (1,25(OH)2 D) and their mode of degradation. In this presentation I will provide an overview of how the body handles these different forms of vitamin D.