Vitamin D3 has many important functions in the body and is important in maintaining overall health.

It also helps brain function, contributes to strong bones, and aids in fighting infection. The body uses vitamin D3 to regulate the amount of calcium in the bloodstream.

The symptoms of vitamin D deficiency can be nonspecific such as fatigue, aches, and pains.

Other people who have vitamin D deficiency may not notice any symptoms. People with a severe vitamin D deficiency can have symptoms like bone pain, weakness, and frequent infections. Other symptoms can include gum disease and frequent fractures of the bones.

There are very few foods that are naturally high in Vitamin D.

Most vitamin D in American diets comes from fortified foods (food to which Vitamin D has been added, such as milk). Fatty fish like tuna, mackerel, and salmon are among the foods naturally highest in Vitamin D. Mushrooms also have some natural Vitamin D content. In addition to milk, other foods to which Vitamin D is typically added include breakfast cereals and some types of orange juice and yogurt.

Yes.

It is possible to have too much Vitamin D. This most commonly occurs when people take too many Vitamin D supplements. Signs of Vitamin D toxicity can include decreased appetite, nausea, vomiting, weakness, constipation, and weight loss. Too much Vitamin D can also raise calcium levels that can lead to heart rhythm disturbances, confusion, and disorientation.