The invention provides compositions and methods for delivering vitamin D to a human subject. In one embodiment the invention provides a transdermal patch for the transdermal administration of vitamin D comprising: (a) a backing layer that serves as the outer surface of the patch during use； (b) an adhesive drug reservoir layer for affixing the patch to human skin； and (c) a release liner, which upon removal exposes the adhesive drug reservoir layer. The adhesive drug reservoir layer can include vitamin D, a polymeric adhesive, an organic solvent, and a permeation enhancer.
