Side effects of taking vitamin D3 include difficulty swallowing, rapid heartbeat, dizziness, chest tightness and swelling of facial features, according to Drugs.com. More side effects are hives, skin rash, weakness and fatigue. Vitamin D3 can also cause metabolic side effects, such as hypercalcemia.
Vitamin D3 is also known as the generic drug cholecalciferol, states Drugs.com. It is one of the five types of vitamin D and functions as a prehormone. It is used to treat calcium deficiencies in the body, such as osteoporosis, softening of bones, rickets and changes in bones due to renal failure, notes WebMD.
If side effects are experienced, it is important to seek immediate medical attention.