Why do we correct calcium for albumin?

About half of serum calcium is bound to albumin. If albumin levels are low, the total measured calcium will be low even if the active (ionized) calcium is normal.

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MedicoDoctorMedical Laboratory Scientist

Corrected Calcium Calculator

Calculate serum calcium levels corrected for albumin, providing a more accurate reflection of physiologically active calcium.

Calcium is essential for bone health, nerve signaling, and muscle function. However, standard lab tests measure 'total' calcium, which includes calcium bound to proteins like albumin. If albumin is low, the total calcium result can be misleading. This calculator 'corrects' the calcium level to show what it would be if the patient had normal albumin levels.

Educational use only. This tool does not replace clinical judgment or local protocols.

Measured calcium

Albumin (g/L)

Calcium units

Albumin input stays g/L; conversion handled automatically.

Corrected calcium

2.2mmol/L

Corrected Calcium is 2.2 mmol/L

Ca + 0.02 * (40 - Alb) = 2.1 + 0.02 * (40 - 35)

Measured calcium2.1 mmol/L

Albumin (g/L)35 g/L

Unitsmmol/L

Come funziona

The tool uses the standard Payne formula, which adds a correction factor for every unit that the patient's albumin is below the normal reference (usually 4.0 g/dL or 40 g/L).

Formula di calcolo

Ca_corrected = Measured_Ca + 0.8 × (4.0 - Albumin)

Calculation Examples

1. **Low Albumin**: Measured Calcium 8.0 mg/dL, Albumin 2.5 g/dL. Corrected Calcium = **9.2 mg/dL** (Normal).

Why use this tool in your daily life?

Avoid unnecessary treatments. This service prevents the dangerous and costly administration of IV calcium to patients who don't actually need it, keeping electrolyte management safe and evidence-based.