Test Details: Vitamin D 25-hydroxy test is conducted to detect the level of vitamin D present in your body. Vitamin D 25-hydroxy is a fat soluble vitamin and People with a vitamin D deficiency become prone to heart diseases, high blood pressure, immune system disorders, different types of cancers (prostrate, breast and colon) and various infectious diseases. Vitamin D helps in maintaining strong bones and teeth. Vitamin D is also useful in regulating levels of phosphorus, magnesium and calcium in the body. Vitamin D has also been known to influence the growth and differentiation of many other tissues in the body and helps in regulating the immune system.