Hypervitaminosis D is a condition related to the overconsumption of Vitamin D supplements. It is never found in persons who rely solely on diet (or even exposure to sunshine) to obtain their supply of the vitamin. It is often associated with Vitamin K deficiency as Vitamin K also regulates calcium in the body. The amount of Vitamin D necessary to cause hypervitaminosis is on the order of 100 times the recommended daily allowance of the vitamin for a period of several months.
Vitamin D is critical to the use of calcium to form bones. However, when consumed in excess, the body also maintains a higher level of calcium in the bloodstream. This does not occur with Vitamin D obtained through exposure to ultraviolet light as the chemistry of making the dietary supplement available does not simultaneously counterbalance the amount of Vitamin D available. The high calcium levels then interfere with other metabolic functions.
However, once established, the condition requires more than merely discontinuing supplements. The patient has to be put on a low-calcium diet and given steroids for a period of about one month until calcium levels return to normal.