Vitamin D bụ vitamin ma bụrụkwa homonụ steroid, nke gụnyere VD2 na VD3, nke usoro ha yiri nnọọ. Vitamin D3 na D2 na-atụgharị gaa na 25 hydroxyl vitamin D (gụnyere 25-dihydroxyl vitamin D3 na D2). 25- (OH) VD n'ime ahụ mmadụ, nkwụsi ike struction, elu itinye uche. 25- (OH) VD na-egosipụta ọnụọgụ vitamin D zuru oke, na ikike ngbanwe nke vitamin D, ya mere 25- (OH) VD na-ewere dị ka ihe ngosi kachasị mma maka ịlele ọkwa vitamin D. Ihe nchọpụta nchọpụta dabeere na ya. Immunochromatography ma nwee ike inye nsonaazụ n'ime nkeji iri na ise.