Vitacal Calcium is used to prevent or treat hypocalcemia in individuals who do not get enough calcium through their diet. Vitacal is essential for proper bone growth and formation. Vitamin D3, also known as calcitriol, plays a key role in improving calcium absorption into the blood. Vitamin D3 also helps regulate essential minerals in the body, such as calcium and phosphorus. A deficiency in vitamin D3 can lead to weak bones, bone pain, and skin problems.