This represents the amount of calcium in your blood and is an essential mineral in the body, crucial for bone and teeth health, muscle contraction, nerve function, and blood clotting. If your calcium levels are too high, this can indicate thyroid disease, lung disease, kidney failure, cancers, or other illnesses. If your calcium is too low, this can indicate a thyroid disease, kidney disease, vitamin D deficiency, Celiac disease, or other conditions.