The normal range for Vitamin D in the blood is 30 to 74 nanograms per milliliter, according to the U.S. National Library of Medicine. The level is determined with the 25-hydroxy vitamin D test.
The 25-hydroxy vitamin D is processed in the kidneys to become an active type of the vitamin, the U.S. National Library of Medicine states. The active vitamin D controls levels of phosphorus and calcium in the body. Low vitamin D levels are caused by not getting enough sunlight or nutrients from food high in this vitamin, liver or kidney problems, or a side-effect from taking particular medications, including phenytoin, phenobarbital and rifampin. Too much vitamin D is often caused by a condition called hypervitaminosis D.