Vitamin D (25-Hydroxy)

A Vitamin D (25-Hydroxy) test measures the levels of vitamin D in the body. It is an essential nutrient that can be synthesized in the body upon healthy exposure to sunlight or absorbed from dietary sources. It majorly exists in two forms: Vitamin D2 (ergocalciferol) and Vitamin D3 (cholecalciferol). Vitamin D2 is present in plants, such as yeast or mushrooms, and is available as a supplement in fortified foods, and vitamin D3 is found in foods like cheese, green vegetables, mushrooms, egg yolks, and fatty fish.

Both forms of vitamin D (D2 and D3) need to undergo some chemical changes before being available for use in the body. These chemical changes take place in the liver or kidneys. The liver converts vitamin D to 25-hydroxyvitamin D (25-OH vitamin D). A Vitamin D (25-Hydroxy) test measures the level of this 25-OH vitamin D as it is the primary form of vitamin D that circulates in the blood.