Normal Range: 30-100 ng/mL

Vitamin D is a fat-soluble vitamin that comes in two forms⁸: vitamin D2 (found in dietary supplements, fortified foods⁹ and mushrooms exposed to sunlight¹⁰) and vitamin D3 (produced in the skin by sunlight and found in foods, such as fish, organ meats, egg yolks³, dietary supplements and fortified foods 9). Both forms are used by the body in the same way; the only difference between the two is the structure of their side chains11. Vitamin D is important for the absorption of calcium and phosphorus¹². Poor absorption of these minerals due to vitamin D deficiency could lead to decreased bone mineralization, osteopenia, and osteoporosis⁸. In the elderly, a vitamin D deficiency increases the risk for falls and fractures13. Those who get inadequate sun exposure or have darker skin are at higher risk for a vitamin D deficiency, as are those who are unable to absorb dietary fat, and those who are obese or who have recently had a gastric bypass surgery⁸.