What is Total 25-Hydroxyvitamin D (Capillary Dried Blood Spot)?
25-Hydroxyvitamin D is the major circulating vitamin D metabolite and the accepted index of vitamin D stores, with a half-life of roughly two to three weeks. In a dried-blood-spot specimen it is measured from capillary whole blood dried onto a filter card, so the result reflects a whole-blood matrix rather than separated serum; laboratories apply method-specific calibration to report a value aligned to circulating 25-OH-D. The measurement here is total 25-OH-D by LC-MS and is not reported as separate D2 and D3 fractions.