Corrected calcium for albumin
- Category: Renal and metabolic
- Version: v1.0.1
- Reviewed: Reviewed 6 Sep 2026
- Validation: Validation pending
Corrected calcium (mg/dL) = measured total calcium + 0.8 × (4.0 − serum albumin in g/dL). In SI units: corrected calcium (mmol/L) = measured + 0.02 × (40 − albumin in g/L). The result is reported in both conventions, with ÷ 4.008 between them. The 0.8 is the rounded form of Payne’s original 1.0 slope.
No bands: read the result against the age-specific paediatric total-calcium reference range (Roizen 2013). Unreliable in critical illness: adjusted calcium tracked ionized calcium poorly (sensitivity 78%, specificity 63%, AUC 0.78 for ionized hypocalcemia; Steele 2013), so ionized calcium is the reference standard in the critically ill, in acid-base disturbance, after citrate-containing transfusion, and with rapid albumin shifts. The fixed linear coefficient overestimates ionized calcium at low albumin, and the slope is assay- and population-specific. Payne’s cohort was 200 adults with no ionized validation, and no paediatric derivation exists, so prefer ionized calcium in neonates and unstable children.
References
- Payne RB, Little AJ, Williams RB, Milner JR. Interpretation of serum calcium in patients with abnormal serum proteins. Br Med J. 1973;4(5893):643–646.PMID 4758544DOI 10.1136/bmj.4.5893.643
- Steele T, Kolamunnage-Dona R, Downey C, Toh CH, Welters I. Albumin-adjusted calcium concentration should not be used to identify hypocalcaemia in critical illness. Crit Care. 2013;17(Suppl 2):P446.DOI 10.1186/cc12384
- Roizen JD, Shah V, Levine MA, Carlow DC. Determination of Reference Intervals for Serum Total Calcium in the Vitamin D-Replete Pediatric Population. J Clin Endocrinol Metab. 2013;98(12):E1946–E1950.PMID 24217904DOI 10.1210/jc.2013-3105
Reproduction rights
Freely reproducible.Linear arithmetic transformation of two lab values with a numeric coefficient (0.8/0.02) and reference constant (4.0 g/dL); facts and mathematics, no proprietary scale text (corrected-calcium.md IP status).
Independent clinical validation: pending
Two independent clinical validators will be named here once review is complete.
- 2026-09-03v1.0.0Initial releaseInitial published text.
- 2026-09-06v1.0.1ClarificationAdded a one-line description for the catalogue card. No rule, threshold or reference changed.
Other renal and metabolic scores
- Anion gapAnion gap from electrolytes, with an albumin-corrected value for hypoalbuminaemia
- Corrected sodium for hyperglycemiaMeasured sodium adjusted for hyperglycaemia, by both published factors
- KDIGO AKI stagingAcute kidney injury stage from creatinine and urine output
- Serum osmolality and osmolar gapCalculated osmolality and the osmolar gap, with ethanol accounted for
Important. For use by qualified health professionals as an informational and educational aid. It supports clinical judgment and does not replace it. Verify every result independently before making a clinical decision. This is not a medical device.