Vitamin D is also known as the "sunshine vitamin" because the body manufactures the vitamin after being exposed to sunshine. Ten to 15 minutes of sunshine 3 times weekly is enough to produce the body's requirement of vitamin D. Needed for strong bones and teeth, Vitamin D helps your body absorb the amount of calcium it needs. It also has other roles in the body, including modulation of cell growth, neuromuscular and immune function, and reduction of inflammation. There are associations between low Vitamin D levels and peripheral vascular disease, certain cancers, multiple sclerosis, rheumatoid arthritis, juvenile diabetes, Parkinson's, and Alzheimer's disease. Measurement of serum 25-OH vitamin D concentrations provide a good index of circulating vitamin D activity in patients not suffering from renal disease. Lower than normal 25-OH vitamin D levels can result from a dietary deficiency, poor absorption of the vitamin or impaired metabolism of the sterol in the liver. A 25-OH vitamin D deficiency can lead to bone diseases such as rickets and osteomalacia. Above normal levels can lead to hypercalcemia. This assay employs liquid chromatography tandem mass spectrometry to independently measure and report the two common forms of 25-hydroxy vitamin D: 25-OH D3 - the endogenous form of the vitamin and 25-OH D2 - the analog form used to treat 25-OH Vitamin D3 deficiency. Includes: Vitamin D, 25-OH, Total Vitamin D, 25-OH, D3 Vitamin D, 25-OH, D2