Vitamin D is essential for good bone health and possibly other important functions, including protection against autoimmune diseases and cancers. This test measures the total reserves of vitamin D3 (produced by exposure to sunlight and found in animal-based supplements) and vitamin D2 (plant-based, found in most supplements). Low sun exposure, certain medications, malnutrition and intestinal malabsorption are the most common causes of vitamin D deficiency.
Below normal vitamin D levels may be associated with bone diseases such as rickets (in children) and osteomalacia (in adults). Levels above 50 nanomoles per litre (nmol/L) appear to be sufficient to ensure good bone health (protection against osteoporosis, etc.), while levels above 75 nmol/L would be required for possible protection against cancers and autoimmune diseases.
Above normal levels of vitamin D reflect excessive supplementation. When calcium levels are also high, the individual may experience the effects of hypercalcemia (see your calcium test result). In the long term, high vitamin D levels can lead to the calcification of soft tissues including the kidneys, the formation of kidney stones and weakening of the bones (resorption).