Corrected Calcium for Albumin (Payne Formula)
Adjusts measured serum calcium for albumin levels to estimate physiologically active calcium. Based on the Payne formula developed in 1973.
Warnings:
- Payne formula was derived from 200 patients at a single laboratory; accuracy varies with severe hypoalbuminemia
- Ionized calcium (iCa) is the gold standard for assessing calcium status when available
- Studies show uncorrected total calcium may correlate better with iCa than corrected calcium in some populations
- For SI units (mmol/L): adjusted calcium = total calcium (mmol/L) + 0.02 * [40 - albumin (g/L)]
- Multiple correction formulas exist; this calculator uses the most commonly used simplified Payne formula
Note: Alternative formula for mmol/L: Ca_corrected (mmol/L) = Ca_measured (mmol/L) + 0.02 x (40 - Albumin [g/L]). Consider measuring ionized calcium directly in patients with significant hypoalbuminemia.
Serum total calcium from laboratory measurement
Serum albumin level. Normal albumin is typically 4.0 g/dL
References
- Use of Albumin-Adjusted Calcium Measurements in Clinical Practice - JAMA Network Open (2025)
- Things We Do for No Reason: Calculating a Corrected Calcium Level - Journal of Hospital Medicine / TWDFNR (2021)