He huaora ka Vitamin D a he hormone steroid hoʻi, ʻo ia hoʻi ʻo VD2 a me VD3, nona ke ʻano hana like loa. Hoʻololi ʻia ka Vitamin D3 a me D2 i 25 hydroxyl vitamin D (me 25-dihydroxyl vitamin D3 a me D2). 25-(OH) VD i loko o ke kino kanaka, paʻa ke ʻano hana, kiʻekiʻe ka nui. Hōʻike ka 25-(OH) VD i ka nui o ka huaora D, a me ka hiki ke hoʻololi i ka huaora D, no laila ua manaʻo ʻia ʻo 25-(OH) VD ka hōʻailona maikaʻi loa no ka loiloi ʻana i ka pae o ka huaora D. Hoʻokumu ʻia ka Diagnostic Kit ma ka immunochromatography a hiki ke hāʻawi i kahi hopena i loko o 15 mau minuke.