Can vitamin D metabolite measurements facilitate a “treat-to-target” paradigm to guide vitamin D supplementation?

Summary Substantial variability exists in the serum 25(OH)D increase observed in response to vitamin D supplementation. Measurement of circulating cholecalciferol and 24,25(OH)2D, as indicators of vitamin D absorption and degradation, respectively, account for approximately half of the variation in serum 25(OH)D observed following supplementation.