25-OH VITAMIN D (TOTAL) (THY)
The major circulating form of vitamin D is 25-hydroxyvitamin D (25(OH)D); thus, the total serum 25(OH)D level is currently considered the best indicator of vitamin D supply to the body from cutaneous synthesis and nutritional intake. The reference range of the total 25(OH)D level is 25-80 ng/mL.
The 25-hydroxy vitamin D test is the most accurate way to measure how much vitamin D is in your body. Vitamin D helps control calcium and phosphate levels in the body. Blood is drawn from a vein (venipuncture), usually from the inside of the elbow or the back of the hand.