Corrected Calcium Calculator

Roughly 50% of total serum calcium is bound to proteins, primarily albumin. When albumin drops, total calcium drops, but the physiologically active ionized calcium may remain normal. This formula adjusts the total calcium to what it "would be" if the albumin were normal (4.0 g/dL).

First derived by Payne et al. in 1973. Before the widespread availability of direct ion-selective electrodes to measure ionized calcium, clinicians needed a reliable heuristic to interpret total calcium panels in the context of malnutrition and liver disease.