Corrected Calcium Calculator
Adjust total calcium for albumin and assess true calcium status using the Payne correction formula.
Core Lab Tools provide rapid calculations and can be extended into full Clinical Intelligence Systems.
Input & Computation
For every 10 g/L fall in albumin below 40 g/L, total calcium falls by approximately 0.2 mmol/L — without any change in the physiologically active ionised fraction. Uncorrected calcium can mask true hypercalcaemia in cancer patients with low albumin.
Enter Values
Albumin in g/L. Use the unit toggle for calcium.
Normal: 35–50 g/L. Correction is most relevant when albumin < 35 g/L.
Interpretation Guide
Payne Formula
Corrected Ca (mmol/L) = Total Ca + 0.02 × (40 − Albumin g/L)
For mg/dL input: divide by 4 first to convert to mmol/L
Classification (mmol/L)
- < 2.1 mmol/L — Hypocalcaemia
- 2.1–2.6 mmol/L — Normocalcaemia
- > 2.6 mmol/L — Hypercalcaemia
Evidence & References
Payne RB et al. (1973)
Interpretation of serum total calcium: effects of adjustment for albumin concentration on frequency of abnormal values and on detection of change in the individual. Journal of Clinical Pathology 26(12):897–900. Original Payne correction formula.
Ladenson JH et al. (1978)
Relationship of free and total calcium in hypercalcemic conditions. Journal of Clinical Endocrinology & Metabolism 48(3):393–397.
Bushinsky DA & Monk RD (1998)
Electrolyte quintet: Calcium. Lancet 352(9124):306–311. Comprehensive calcium physiology and clinical management review.
Lian IA & Asberg A (2018)
Should total calcium be corrected for albumin? A retrospective observational study of laboratory data from central Norway. BMJ Open 8(4):e017703. Contemporary validation of correction formulas.
CLSI EP28-A3c (2010)
Defines reference intervals for calcium — basis for hypocalcaemia/hypercalcaemia thresholds in clinical decision-making.
Payne correction: Ca_corr = Ca_total + 0.02 × (40 − Albumin g/L). For mg/dL input: divide by 4 to convert. Reference interval: 2.1–2.6 mmol/L. Ionised calcium remains the gold standard; correction is an estimate only.
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PreciMind Clinical Intelligence
Access structured clinical calcium case reasoning, decision frameworks for hypercalcaemia and hypocalcaemia workup, and laboratory interpretation beyond the Payne formula.
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When to Use
- Low total calcium with documented hypoalbuminaemia
- Hospital and ICU patients where albumin is commonly reduced
- Suspected calcium imbalance when ionised calcium is unavailable
- Screening for hypercalcaemia masked by low albumin in cancer patients
- Interpreting calcium in liver disease, nephrotic syndrome, or malnutrition
Common Pitfalls
- ICU use limitations — Payne correction is unreliable in critically ill patients; measure ionised calcium directly
- Ignoring pH effects — acidosis increases ionised calcium; alkalosis decreases it, independent of albumin
- Overreliance on correction — the Payne formula is an estimate with significant individual variation
- Mixing units — albumin must be in g/L (not g/dL) for this formula
- Not validated in CKD, multiple myeloma, or patients with abnormal protein binding