Calcium is only absorbed by your body when it has a proper supply of Vitamin D. And calcium is necessary for the maintenance, health, and growth of your bones. Therefore, Vitamin D plays a vital role in support of and the health of your skeletal. Since Vitamin D deficiency is common amongst almost all age groups now, many people are turning to Vitamin D injections to ensure the body absorbs it. Oral supplements have to pass through your digestive system, decreasing the vitaminβs potency as it is absorbed.