Vitamin D is often called the “sunshine vitamin” because its primary source is the sun but sometimes too much of any good thing is a bad thing. Too much vitamin D can cause an abnormally high blood calcium level, which could result in nausea, constipation, confusion, abnormal heart rhythm, and even kidney stones. Vitamin D can be obtained through three different sources: diet, sunlight and dietary supplements. While the risk of consuming too much vitamin D through diet and sunlight is virtually nonexistent, some people can overdose on vitamin D through supplementation.In fortified supplements and foods, vitamin D is present in two different forms: D-2 and D-3. Both forms of vitamin D can effectively raise the body’s levels of vitamin D. This nutrient helps the body absorb calcium and is necessary for bone growth. A lack of vitamin D can cause a number of conditions, including brittle bones, osteoporosis and rickets in children.