Determination of vitamin D conjugated metabolites: a complementary view on hydroxylated metabolites.

Experts typically define vitamin D deficiency levels by the determination of a circulating 25-hydroxyvitamin D-calcifediol prohormone. A large part of the population is characterized by deficient vitamin D levels (calcifediol < 20 ng mL) despite individuals not being affected by any disorder. Cholecalciferol (vitamin D) and/or calcifediol supplementation is a common practice for vitamin D-deficient individuals as recommended by international scientific societies and official agencies.