VITAMIN D INJECTION Vitamin D affects many organ systems, but it primarily helps to increase calcium and phosphate absorption from the intestines and promotes the formation of mineralisation within the bones. Vitamin D helps regulate the amount of calcium and phosphate in the body. These nutrients are needed to keep bones, teeth and muscles healthy. A deficiency of vitamin D can be the result of many factors including; lack of exposure to sunlight, reduced intake of vitamin D in the diet, a reduction in the absorption of vitamin D, the body becoming resistant to the effects of vitamin D.