What is 25-Hydroxyvitamin D2 (Ergocalciferol)?
25-Hydroxyvitamin D2 is the hepatic 25-hydroxylation product of ergocalciferol, the plant- and fungus-derived vitamer supplied almost exclusively by prescription-strength oral vitamin D2 in most territories. It circulates bound to vitamin D-binding protein and, like D3, requires a second renal 1-alpha-hydroxylation to the active 1,25-dihydroxy form. D2 has a shorter serum half-life and lower binding-protein affinity than D3, so its contribution to measured total 25-OH-D falls more quickly between doses.