Health
Corrected Calcium Calculator
Adjust serum calcium for low albumin (Payne formula). Get status (hypocalcemia, normal, hypercalcemia) and a rough ionized calcium estimate.
Lab values
Corrected calcium
8.8 mg/dL
(2.2 mmol/L), status: low normal
- Correction applied
- +0.8 mg/dL
- Ionized estimate (rough)
- 4.4 mg/dL
Educational only. Real ionized calcium requires direct measurement; clinical use requires lab values and physician interpretation.
Frequently Asked Questions about the Corrected Calcium Calculator
Why does serum calcium need correction for albumin?
About 40 percent of serum calcium is bound to albumin. When albumin is low (hypoalbuminemia from liver disease, malnutrition, or critical illness), total serum calcium falls without any actual change in the biologically active ionized fraction. The Payne formula adjusts total calcium back to what it would read at a normal albumin of 4.0 g/dL.
What is the Payne formula?
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.
What is a normal corrected calcium?
Most labs report 8.5 to 10.5 mg/dL (2.13 to 2.63 mmol/L) as the reference range. Below 8.5 is hypocalcemia; above 10.5 is hypercalcemia. The calculator flags the corrected value against these thresholds.
Is corrected calcium the same as ionized calcium?
No. Ionized (free) calcium is the physiologically active fraction and the most accurate measurement, but it requires a special blood gas analyzer with strict handling. Corrected calcium is a quick estimate from a regular comprehensive metabolic panel. When precision matters (critical care, dialysis, parathyroid workup), order ionized calcium directly.
Is this calculator a substitute for medical advice?
No. Educational use only. Clinical interpretation requires the full patient context, recent labs, and physician judgment. Do not change treatment based on this output.