Many experts recommend a range of 20 to 40 nanograms per milliliter of vitamin D2, while others recommend a level between 30 to 50 nanograms per milliliter, notes MedlinePlus. These measures are common results of tests carried out to determine vitamin D levels.
Normal levels vary from one laboratory to another due to different test samples or measurements, states MedlinePlus. Lower than normal values result from vitamin D deficiency, which occurs due to poor food absorption, kidney diseases, lack of sunlight exposure and insufficient vitamin D in the diet. Elevated levels may result from a condition called hypervitaminosis, excess levels of vitamin D. Patients can undergo the 25-hydrocy vitamin D test to determine their personal levels.