Individuals with normal calcium levels have a decreased risk of developing health conditions that occur when calcium levels are either higher than normal or lower than normal. According to MedlinePlus, all cells require calcium to work, but abnormal calcium levels can be a sign of a serious health condition.
Normal calcium levels range from 8.5 to 10.2 milligrams per deciliter. Higher than normal calcium levels are often caused by multiple serious health conditions, including an overactive thyroid gland, a metastatic bone tumor, multiple melanoma, HIV/AIDS and Paget's disease. Lower than normal calcium levels also develop due to serious health issues such as kidney failure, liver disease, a magnesium deficiency, pancreatitis or a vitamin D deficiency, notes MedlinePlus.