Also known as: 25-Hydroxycalciferol, 25-OH-D, Cholecalciferol Metabolite, Vitamin D, Vitamin D3 Metabolite.

Vitamin D tests are used to determine if bone malformation, bone weakness, or abnormal metabolism of calcium (reflected by abnormal calcium, phosphorus or PTH tests) is occurring as a result of a deficiency or excess of vitamin D. Because vitamin D is a fat-soluble vitamin and is absorbed from the intestine like a fat, vitamin D tests are at times used to monitor individuals with diseases that interfere with fat absorption, such as cystic fibrosis and Crohn's disease, to assure that they have adequate amounts of vitamin D. Vitamin D tests are used to determine effectiveness of treatment when vitamin D, calcium, phosphorus, and/or magnesium supplementation is prescribed as well.