Corrected Sodium Calculator
Correct measured serum sodium for hyperglycaemia using both the classic Katz factor and the Hillier correction, to distinguish true hyponatraemia from dilutional pseudohyponatraemia.
Formula & Reference
| Variable | Symbol | Formula | Units |
|---|---|---|---|
| Corrected Sodium Calculator | — | Corrected Na = measured Na + factor × (glucose − 100) / 100 | mmol/L |
Step-by-Step Examples
Measured sodium 128 mmol/L, glucose 600 mg/dL.
- Glucose excess above 100 = 500 mg/dL
- Katz: 128 + 1.6 × 5 = 136 mmol/L
- Hillier: 128 + 2.4 × 5 = 140 mmol/L
- The apparent hyponatraemia is largely dilutional
Measured sodium 132 mmol/L, glucose 300 mg/dL.
- Glucose excess = 200 mg/dL
- Katz: 132 + 1.6 × 2 = 135.2 mmol/L
- Hillier: 132 + 2.4 × 2 = 136.8 mmol/L
Measured sodium 118 mmol/L, glucose 700 mg/dL.
- Glucose excess = 600 mg/dL
- Katz: 118 + 1.6 × 6 = 127.6 mmol/L
- Even fully corrected, sodium remains clearly low
- Indicates genuine sodium depletion alongside hyperglycaemia
Real-World Applications
Common Mistakes to Avoid
Correction estimates what sodium would be once glucose normalises. It is a projection, not a measurement, and both correction factors are approximations.
The 1.6 factor was derived at moderate hyperglycaemia. Experimental work by Hillier suggested 2.4 fits better above roughly 400 mg/dL, and using 1.6 there underestimates the correction.
Severe hypertriglyceridaemia and paraproteinaemia cause a different laboratory artefact affecting the measurement method itself, which no glucose-based correction addresses.