Vitamin D (ergocalciferol-D2, cholecalciferol-D3, alfacalcidol) is a fat-soluble vitamin that helps your body absorb calcium and phosphorus.
Having the right amount of vitamin D, calcium and phosphorus are important for building and keeping strong bones. Vitamin D is used to treat and prevent bone disorders.
Vitamin D is made by the body when the skin is exposed to sunlight. Sunscreen, protective clothing, limited exposure to sunlight, dark skin, and age may prevent getting enough vitamin D from the sun.
Vitamin D is also used with other medications to treat low levels of calcium or phosphate caused by certain disorders
It may be used in kidney disease to keep calcium levels normal and allow normal bone growth. Vitamin D drops (or other supplements) are given to breast-fed infants because breast milk usually has low levels of vitamin D.