Calcifediol (
INN), also known as
calcidiol,
25-hydroxycholecalciferol, or
25-hydroxyvitamin D (abbreviated
25(OH)D), is a
prehormone that is produced in the
liver by
hydroxylation of
vitamin D3 (cholecalciferol) by the enzyme
cholecalciferol 25-hydroxylase which was isolated by
Michael F. Holick. Physicians worldwide measure this metabolite to determine a patient's vitamin D status. At a typical daily intake of vitamin D3, its full conversion to calcifediol takes approximately 7 days.