The 25-hydroxy Vitamin D test measures the Vitamin D levels in the body. Vitamin D is an essential vitamin for humans. The human body requires Vitamin D for regulating body minerals. Vitamin D helps to maintain Calcium and Phosphorus balance in the body. Vitamin D, also known as calciferol, is a fat-soluble vitamin. Vitamin D functions in the capacity of a hormone. Find Vitamin D Test price at an HOD centre near you.