I-Vitamin D yivithamin kwaye ikwayi-hormone ye-steroid, ingakumbi i-VD2 kunye ne-VD3, umyalelo wayo ufana kakhulu. I-Vitamin D3 kunye ne-D2 iguqulwa ibe yi-25 i-hydroxyl i-vitamin D (kuquka i-25-dihydroxyl i-vitamin D3 kunye ne-D2). I-25-(OH) i-VD emzimbeni womntu, umyalelo ozinzileyo, ukugxila okuphezulu. I-25-(OH) i-VD ibonisa inani elipheleleyo levithamini D, kunye nokukwazi ukuguqulwa kwe-vitamin D, ngoko i-25-(OH) VD ithathwa njengesona salathisi sokuvavanya izinga le-vitamin D.I-Diagnostic Kit isekelwe i-immunochromatography kwaye inokunika umphumo kwimizuzu eyi-15.