A calcium lab test or a calcium blood test is performed to measure either of the two - the total calcium level or the ionized calcium level. Normally, the calcium level in our body is well controlled. There is a balance between the free calcium (ionized) present in blood and the stored calcium present in bones. This test helps to diagnose and treat conditions that may have arisen from very high or very low calcium levels. Bone diseases, neurologic disorders, kidney failure, muscle spasm, thyroid malfunction and heart problems are caused by abnormal calcium levels.