Vitamini D ndi vitamini ndipo alinso mahomoni a steroid, makamaka vd2 ndi vd3, yemwe akuphatikiza kwake ndi zofanana kwambiri. Vitamini D3 ndi D2 amasinthidwa kukhala 25 hydroxyl vitamini d (kuphatikiza 25-dihhdroxyl vitamini d3 ndi d2). 25- (oh) VD m'thupi la munthu, magawande, chidwi chachikulu. 25- immunochromatograph ndipo imatha kupereka zotsatira zosakwana mphindi 15.