WHAT IS VITAMIN D (CHOLECALCIFEROL) TEST?
Vitamin D is a fat-soluble vitamin found as a dietary supplement in milk and is synthesized in the skin from the body’s cholesterol stores in conjunction with exposure to sunlight and is important in maintaining bone health. Vitamin D is a pro-hormone and becomes biologically active through hepatic hydroxylation to 25-hydroxyvitamin D and then to 1,25-dihydroxy vitamin D through renal hydroxylation. It works in conjunction with calcitonin and parathyroid hormone and is necessary for proper dietary calcium absorption from the intestinal tract, for the regulation of skeletal calcium resorption, and for release of parathyroid hormone. The 2011 Endocrine Society Clinical Practice Guidelines recommend no routine screening of individuals for Vitamin D deficiency; however, this test is recommended as the initial evaluation in individuals with suspected deficiency.
A meta-analysis (Tice, 2011) found that vitamin D supplementation reduces the risk of subsequent bone fracture only when combined with calcium supplementation, and the combination therapy did not increase cardiovascular events. The Institute of Medicine’s recommendations for Vitamin D supplementation are geared toward the goal of bone health and recommend 600 IU per day for clients age 70 and under, and 800 IU per day for those over age 70.