Vitamin D bụ vitamin ma bụrụkwa hormone steroid, nke gụnyere VD2 na VD3, nke nhazi ya yiri nke ukwuu. A na-agbanwe Vitamin D3 na D2 ka ọ bụrụ vitamin D hydroxyl 25 (gụnyere vitamin D3 na D2 25). 25-(OH) VD n'ahụ mmadụ, nhazi siri ike, oke njupụta. 25-(OH) VD na-egosipụta mkpokọta vitamin D, yana ikike mgbanwe nke vitamin D, yabụ a na-ewere 25-(OH) VD dị ka ihe ngosi kacha mma maka ịtụle ọkwa vitamin D. Ngwa nchọpụta ahụ dabere na immunochromatography ma nwee ike inye nsonaazụ n'ime nkeji iri na ise.