The Vitamin D test measures the level of Vitamin D in your blood. When exposed to sunlight, your skin can produce its own Vitamin D. Foods fortified with Vitamin D are also good sources of Vitamin D. Your body stores an inactive form of Vitamin D in fat cells until it is needed for use. The liver and the kidneys convert inactive Vitamin D to 25 hydroxyvitamin D, the active form the body needs. Our blood test measures the amount of 25 hydroxyvitamin D, an indicator for the level of Vitamin D in your body. Abnormal levels of Vitamin D can indicate bone disease, nutrition disorders, or other metabolic complications.