Vitamin D plays a vital role in calcium absorption, and its deficiency can lead to abnormal bone development, weakness, and pain. It also helps maintain proper calcium, phosphate, and parathyroid hormone levels. Parathyroid hormone (PTH) controls the level of calcium in the blood. This test is often done to find the cause of hyper or hypocalcemia, osteoporosis, kidney stones, and low vitamin D levels. In addition, a vitamin profile is done to assess the status of other components, such as vitamin B12, calcium, and magnesium, which are often affected when levels are vitamin D abnormal.