Vitamin D Test
The Vitamin D Test is a serum or dried blood spot analysis that quantitates 25-hydroxyvitamin D2 and 25-hydroxyvitamin D3 metabolites. The metabolite 25-hydroxyvitamin D is the major circulating form of Vitamin D in the body and the best indicator of a patient’s true vitamin status. The major biologic function of Vitamin D is to maintain the normal blood levels of calcium and phosphorus involved in bone mineralization. Vitamin D also influences expression of more than 2,000 genes, including those responsible for regulation of cellular proliferation, cell differentiation, apoptosis, and angiogenesis. The immune-modulating effects of Vitamin D are profound, as evidenced by the many conditions that are associated with Vitamin D deficiency.
Vitamin D deficiency has been linked to increased risk for many common and serious diseases, including some common cancers, diabetes, cardiovascular disease, and osteoporosis. Deficiency is also prevalent in infants who are solely breastfed and who do not receive Vitamin D supplementation. Adults of all ages who have darker skin (increased skin melanin) or who always wear sun protection or limit their outdoor activities, such as homebound elderly persons, are also prone to Vitamin D deficits.
Studies suggest that exposure to sunlight enhances the production of Vitamin D in the skin and prevents many chronic diseases. Seasonal depression is also linked with low levels of Vitamin D, especially during the winter months when sunlight exposure is at a minimum. Vitamin D can also come from supplementation and diet, but there are very few foods (fatty fish, fish liver oil, and eggs) that naturally contain Vitamin D. Several foods claim to be fortified with Vitamin D, but the synthetic form isn't as potent and doesn't last as long in the body.
The Vitamin D Test can help to determine if sun exposure is adequate, if dietary Vitamin D is sufficient, and to assess the likelihood of malabsorption or liver disease.