Vitamin profile test is used to diagnose vitamin D, vitamin B12 and micronutrient deficiency in the blood. It measures 25 hydroxy vitamin D levels. If the levels are abnormal, PTH levels in blood are tested along with active vitamin B12, calcium and magnesium levels. Low vitamin D levels can help diagnose a case of secondary hyperparathyroidism. PTH test is most often used along with vitamin D levels to diagnose hypoparathyroidism & monitor kidney disease. It is also used to diagnose cause for osteoporosis & kidney stones. Vitamin B12, calcium and magnesium levels are also important for efficient functioning of nerves, muscles and even cardiac health.