Clinical Overview
The Corrected Calcium Calculator is utilized daily in internal medicine to interpret basic metabolic panels. True hypocalcemia can cause arrhythmias and tetany, but "pseudohypocalcemia" due to hypoalbuminemia requires no treatment.
Pathophysiology & Evidence
Calcium exists in the blood in three states: ionized (active), bound to anions, and bound to proteins (primarily albumin). Routine labs measure total calcium. In malnourished or critically ill patients with low albumin (< 4.0 g/dL), total calcium falls, but the active ionized portion remains unchanged.
Formula Breakdown
Corrected Calcium = Measured Ca + 0.8 * (4.0 - Serum Albumin)
For every 1 g/dL drop in albumin below 4.0, total calcium drops by 0.8 mg/dL. This formula corrects the total calcium to what it would be if the albumin were normal.