General and clinical
Corrected calcium
About half of serum calcium is bound to albumin, so a low albumin makes total calcium look low when the free, active fraction is normal. This adjusts the measured value for the albumin.
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This calculator is provided for reference and education. It does not replace clinical assessment, examination, current guidelines, local protocol, or professional judgment. Verify every result before acting on it. Nirogix accepts no liability for clinical decisions made using this tool.
The formula
- Corrected calcium = measured calcium + 0.8 × (4.0 − albumin g/dL)
Worked example
Calcium 7.6 mg/dL with albumin 2.5 g/dL → 7.6 + 0.8 × 1.5 = 8.8 mg/dL, which is within range
When to use it
- Interpreting a calcium result in a patient with low albumin, such as nephrotic syndrome, liver disease, malnutrition or critical illness
And when not to
- The correction is an approximation and performs poorly in critical illness and in renal failure.
- Ionized calcium is the measurement, not the estimate. Where the decision matters, order it.
- Acid-base state shifts protein binding independently of albumin.
References
- Correction of total calcium for albumin — Payne RB et al., British Medical Journal, 1973
Last reviewed 07/09/2026.
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