This test measure amount of Ionized calcium. Ionized calcium is calcium in your blood that is not attached to proteins also called as free calcium. Calcium helps build strong bones and teeth. It is important for heart function. It also helps with muscle contraction, nerve signaling, and blood clotting. Ionized calcium levels give more information about active, ionized calcium. If you have abnormal levels of proteins, such as albumin, or immunoglobins in your blood, it may be important to know your ionized calcium levels. If the balance between bound calcium and free calcium is not normal, it’s important to determine why. Free and bound calcium each typically make up half of the body’s total calcium, and an imbalance can be a sign of a major health issue. Patients receiving blood transfusions, critically ill patients on intravenous fluids, patients undergoing major surgery, and patients with abnormal levels of blood proteins may have their ionized calcium levels checked. In these patients, it is important to understand exactly how much free calcium is available. Low levels of free ionized calcium can cause the heart to slow down or speed up, can cause muscle spasms, and can even result in coma. If you have any signs of numbness around your mouth or in your hands and feet, or experience muscle spasms in the same areas, an ionized calcium test may be ordered. This test is more difficult to perform than a serum calcium test due to the special handling required for the blood sample, so it is only done in certain circumstances.