Vitamin D yog vitamin thiab kuj tseem yog tshuaj steroid tshuaj, feem ntau yog suav nrog VD2 thiab VD3, uas nws txoj kev sib tw zoo heev. Vitamin D3 thiab D2 tau hloov dua siab tshiab txog 25 hydroxyl vitamin d (suav nrog 25-Dihydroxyl vitamin D3 thiab D2). 25- (Huag) VD hauv tib neeg lub cev, kev sib tsoo ruaj khov, siab siab. 25- (Oh) VD hais txog tag nrho cov vitamin D, thiab kev hloov pauv ntawm cov vitamin D, yog li 25- (((Oh) VD yog raws li impunochromium thiab tuaj yeem muab qhov tshwm sim hauv 15 feeb.