Vitamin D2 (25-OH D2)

25-hydroxyvitamin D2 [25(OH)D2] is the measured form of Vitamin D2 (Ergocalciferol), derived from plant sources and often used in fortified foods or supplements. It contributes to total vitamin D status [Total 25(OH)D = 25(OH)D2 + 25(OH)D3] but is generally considered less potent and has a shorter half-life than D3. This test is usually only needed if specifically supplementing with D2 or if total D levels are unexpected.