Ionized Calcium

What is Ionized Calcium?

Ionized (free) calcium is the biologically active fraction of blood calcium — about 50 % of total calcium. Unlike the total-calcium measurement, it does not depend on albumin concentration, so it is the more direct reflection of calcium available for muscle contraction, nerve signalling, and enzyme activity.

What might a high or low Ionized Calcium mean?

Symptoms of calcium disturbance (tingling, muscle cramps, fatigue, irregular heartbeat) correlate more closely with ionized calcium than with total calcium. Ionized calcium is the preferred test when albumin is abnormal (liver disease, malnutrition, pregnancy) because the total-calcium result can be misleading in those contexts.

What is the typical reference range for Ionized Calcium?

The general-population reference range shown here is 1.12 – 1.32 mmol/L. Reference ranges describe the general population and are not a personal target — discuss your results with your physician.

What can affect Ionized Calcium?

It may be higher with: Hyperparathyroidism, Vitamin D excess, Some cancers, Prolonged immobilization, Thiazide diuretics. It may be lower with: Hypoparathyroidism, Severe vitamin D deficiency, Chronic kidney disease, Magnesium deficiency, Acute pancreatitis.