Vitamin D3 (Cholecalciferol) can be used to treat osteoporosis and also be used to treat conditions in which vitamin D3 levels may be low, such as in people who have underactive parathyroid glands, low levels of phosphate in the blood, or hereditary conditions in which the body doesn’t respond to the parathyroid hormone. Vitamin D3 also encourages the kidneys to recycle phosphate back into the blood, which helps the blood stay at the right pH.

Serious side effects of vitamin D3 include allergic reactions like rash or itching, swelling of the face, throat, and tongue, severe dizziness, trouble breathing, and changes in heart rhythm. Some rare side effects are dry mouth, headache, vomiting, weakness and lack of energy and fatigue.