IVithamini D yivithamini kwaye ikwayi-hormone ye-steroid, ikakhulu equka i-VD2 kunye ne-VD3, eyakhiwe ngendlela efanayo kakhulu. IVithamini D3 kunye ne-D2 ziguqulwa zibe yi-25 hydroxyl vitamin D (kuquka i-25-dihydroxyl vitamin D3 kunye ne-D2). I-25-(OH) VD emzimbeni womntu, ulwakhiwo oluzinzileyo, uxinaniso oluphezulu. I-25-(OH) VD ibonisa isixa siphela sevithamini D, kunye nokukwazi ukuguqula ivithamin D, ngoko ke i-25-(OH)VD ithathwa njengeyona nto ibalaseleyo yokuvavanya inqanaba levithamin D. I-Diagnostic Kit isekelwe kwi-immunochromatography kwaye inokunika isiphumo kwimizuzu eli-15.