Vitamin D is a fat-soluble vitamin critical to calcium absorption which helps in bone growth, density, and strength. Without sufficient vitamin D, bones can become brittle or misshapen. Varying levels of vitamin D in the blood are associated with common variants in the following genes: (1) GC (transports vitamin D to organs), (2) NADSYN1/DHCR7 (needed for bioavailability of the vitamin D precursor molecule), and (3) CYP2R1 (helps convert inactive vitamin D to it’s active form). Maintaining adequate levels of Vitamin D has been shown to benefit patients in the maintenance of bone health for osteoporosis treatment, and in the prevention of fractures.