Vitamin D2-d6 is form of Vitamin D2 that has been chemically labeled with deuterium, a stable and non-radioactive isotope of hydrogen. This specific labeling does not change the biological activity of Vitamin D2 significantly but makes it possible to trace the vitamin in biological and chemical systems. The main uses of such labeled compounds are in research and analytical settings. Applications include: Metabolic studies, pharmacokinetics, nutritional research, bioavailability studies, and mechanism of action studies.