What does the Total Serum Calcium test measure?

Why is Total Serum Calcium measured?

Total serum calcium is measured on almost every metabolic panel and serves as the initial screen for disorders of calcium homeostasis. Because almost half is protein-bound, total calcium must be interpreted in the context of serum albumin; a low albumin spuriously lowers total calcium even when ionised calcium is normal. Abnormalities prompt evaluation of parathyroid function, vitamin D status, renal function, and malignancy, and persistent dysregulation can signal hyperparathyroidism, malignancy-associated hypercalcaemia, vitamin D toxicity, or hypoparathyroidism.

Reference ranges

Standard reference

Approximately 8.5–10.5 mg/dL (2.1–2.6 mmol/L), albumin- and age-dependent.

Functional medicine optimal

Optimal total calcium lies within the laboratory reference range; because it is albumin-dependent, practitioners often apply a correction formula (add 0.8 mg/dL for every 1 g/dL that albumin falls below 4 g/dL) or order ionised calcium when the total is equivocal.

Units

mg/dL, mmol/L

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