The Ionized Calcium test measures the amount of free, biologically active calcium in your blood.2 Calcium exists in three forms in the blood: bound to proteins (mostly albumin), bound to anions (like phosphate and citrate), and the ionized (free) form.
The ionized form is the most important because it is the form that is physiologically active, meaning it is directly responsible for essential functions like:
Because the ionized calcium level is not affected by changes in albumin (unlike the Total Calcium test), it provides a more accurate assessment of a patient's true calcium status, particularly in those who are critically ill or have kidney failure.
