Hypocalcemia describes lower than normal levels of calcium in the blood. This can be caused by abnormally low protein levels (as calcium binds freely to some proteins in the blood), but can also be caused by numerous other conditions. To rule out protein related conditions, the level of ionized calcium in the blood is usually treated as the more accurate figure. Calcium levels should be checked if a patient complains of "CATS go numb" - convulsions, arrythmia, tetany (strong convulsions in the hands), and numbness in the hands, feet, lips and mouth.