Q: Does acidosis affect the correction formula?

The formula does not account for pH changes. Acidosis decreases albumin binding and increases ionised calcium; alkalosis does the opposite. In acid-base disturbances, direct ionised calcium measurement is recommended.

Q: Can I use the correction in patients with monoclonal gammopathies?

Paraproteins can artefactually elevate total calcium without affecting ionised calcium. The standard albumin correction may be inadequate; direct ionised calcium measurement is strongly advised.

Q: What is a clinically concerning corrected calcium level?

Corrected calcium >12 mg/dL (3.0 mmol/L) warrants urgent evaluation for hypercalcaemia of malignancy or primary hyperparathyroidism. Levels >14 mg/dL (3.5 mmol/L) constitute a hypercalcaemic crisis requiring immediate intravenous fluids and anti-resorptive therapy.

Question 1

Is corrected calcium reliable in hypoalbuminaemia?

Accepted Answer

The formula is a reasonable approximation for mild-to-moderate hypoalbuminaemia, but its accuracy is debated for severe hypoalbuminaemia (<20 g/L). Ionised calcium is preferred in this setting.

Question 2

Does acidosis affect the correction formula?

Accepted Answer

The formula does not account for pH changes. Acidosis decreases albumin binding and increases ionised calcium; alkalosis does the opposite. In acid-base disturbances, direct ionised calcium measurement is recommended.

Question 3

Can I use the correction in patients with monoclonal gammopathies?

Accepted Answer

Paraproteins can artefactually elevate total calcium without affecting ionised calcium. The standard albumin correction may be inadequate; direct ionised calcium measurement is strongly advised.

Question 4

What is a clinically concerning corrected calcium level?

Accepted Answer

Corrected calcium >12 mg/dL (3.0 mmol/L) warrants urgent evaluation for hypercalcaemia of malignancy or primary hyperparathyroidism. Levels >14 mg/dL (3.5 mmol/L) constitute a hypercalcaemic crisis requiring immediate intravenous fluids and anti-resorptive therapy.