Corrected Calcium Calculator

A substantial share of circulating calcium is albumin-bound, so total calcium can fall when albumin is low even when ionized calcium does not. The Payne formula attempts to adjust for that relationship, but studies show corrected values can misclassify patients, especially with critical illness, kidney disease, or marked hypoalbuminemia. Measure ionized calcium when the result will affect care.

Corrected calcium (mg/dL) = measured calcium + 0.8 x (4.0 - albumin g/dL). For a measured calcium of 7.5 mg/dL with an albumin of 2.5 g/dL, the correction is 0.8 x 1.5 = 1.2 mg/dL, giving a corrected value of 8.7 mg/dL.

This calculator does not classify the corrected result as low, normal, or high because laboratory ranges and clinical context vary. It also cannot estimate ionized calcium. Compare the measured result with the reporting laboratory's range and use a direct ionized-calcium measurement when accurate classification will affect care.

No. Corrected calcium is an estimate, and albumin-correction formulas can be unreliable in critical illness, chronic kidney disease, and significant hypoalbuminemia. Ionized calcium directly measures the physiologically active fraction and is preferred when an accurate calcium status will change diagnosis or treatment. This calculator cannot substitute for that measurement.

No. Educational use only. Clinical interpretation requires the full patient context, recent labs, and physician judgment. Do not change treatment based on this output.