What does the Calcium (Total) test measure?

Why is Calcium (Total) measured?

Hypercalcaemia (>10.2 mg/dL) is most often due to primary hyperparathyroidism or malignancy; other causes include vitamin D toxicity, granulomatous disease, and immobilisation. Hypocalcaemia (<8.5 mg/dL) suggests hypoparathyroidism, vitamin D deficiency, chronic kidney disease, or hypomagnesaemia. Because albumin binds calcium, total calcium must be corrected for albumin or ionised calcium measured directly when albumin is abnormal.

Reference ranges

Standard reference

8.5–10.5 mg/dL (laboratory-specific); approximately 40% is protein-bound (mainly albumin), 10% complexed, and 50% ionised.

Functional medicine optimal

Mid-normal total calcium (9.0–10.0 mg/dL) is typical when albumin is normal; ionised calcium is more informative in critical illness or hypoalbuminaemia.

Units

mg/dL, mmol/L

Reference ranges vary by laboratory and assay platform. Interpret in context of the issuing laboratory's stated range.