. The ionized calcium (iCa) test measures the amount of free, unbound calcium in the blood, which is the biologically active form that plays a crucial role in various bodily functions such as muscle contraction, nerve function, blood clotting, and bone health.
. This test is particularly useful in evaluating calcium imbalances, as it is not affected by changes in the levels of proteins (such as albumin) that bind calcium in the blood. It is commonly used in cases of suspected hypercalcemia (high calcium levels) or hypocalcemia (low calcium levels), as well as to monitor conditions affecting the parathyroid gland, kidney function, or acid-base balance.