What is the Katz formula for sodium correction?

Katz (1973): Corrected Na = Measured Na + 1.6 × (Glucose − 100) / 100, where glucose is in mg/dL. It assumes sodium drops about 1.6 mEq/L for every 100 mg/dL rise in glucose above the normal threshold of 100 mg/dL.

When should I use the Hillier formula instead?

Hillier et al. (1999) showed that the correction is closer to 2.4 mEq/L per 100 mg/dL in severe hyperglycemia (glucose > 400 mg/dL). Use the 2.4 factor when glucose is markedly high for a more accurate estimate.

What does a corrected sodium above 140 mEq/L mean?

A corrected Na > 140 mEq/L suggests the patient has true hypernatremia masked by the dilutional effect of hyperglycemia-driven water shifts. This indicates significant free-water deficit and guides fluid management.

What is the baseline glucose used in the formula?

The formulas subtract a normal baseline of 100 mg/dL (or 5.5 mmol/L) from the measured glucose before applying the correction factor. No correction is applied when glucose is at or below normal.

Does this tool replace clinical judgment?

No. This calculator is for educational and clinical decision-support purposes only. Always integrate results with the full clinical picture, serum osmolality, and patient history.

Sodium Correction for Glucose Calculator

Calculate the true corrected serum sodium when blood glucose is high, using either the Katz (1.6) or Hillier (2.4) correction formula.

Patient Values

Measured Serum Sodium

mEq/L

Normal range: 135–145 mEq/L

Serum Glucose

Baseline: 100 mg/dL

Correction Formula

Katz (1.6)

Standard formula; suitable for most presentations

Hillier (2.4)

More accurate for glucose > 400 mg/dL

Formula Reference

Katz 1973

Corrected Na = Na_measured + 1.6 × (Glucose − 100) / 100

Hillier 1999

Corrected Na = Na_measured + 2.4 × (Glucose − 100) / 100

Glucose in mg/dL; baseline 100 mg/dL. For mmol/L, baseline is 5.5 mmol/L and increment is per 5.5 mmol/L.

For educational and clinical decision-support only. Results must be interpreted alongside full clinical findings by a qualified clinician.

Summary

Calculate the true corrected serum sodium when blood glucose is high, using either the Katz (1.6) or Hillier (2.4) correction formula.

How it works

Enter the measured serum sodium (Na) in mEq/L.
Enter the serum glucose value and select the unit (mg/dL or mmol/L).
Choose the correction formula: Katz (1.6 factor, standard) or Hillier (2.4 factor, more precise for severe hyperglycemia).
The calculator subtracts the baseline glucose (100 mg/dL or 5.5 mmol/L) from the measured glucose, then applies the correction factor per 100 mg/dL (or 5.5 mmol/L) increment.
The corrected sodium and the correction delta are displayed instantly.

Use cases

Assess true sodium status in diabetic ketoacidosis (DKA).
Evaluate hyperglycemic hyperosmolar state (HHS) sodium balance.
Determine whether hyponatremia is factitious due to hyperglycemia.
Guide IV fluid selection in hyperglycemic emergencies.
Monitor sodium correction as glucose normalizes with insulin therapy.

Frequently Asked Questions

Last updated: 2026-09-19 · Reviewed by Nham Vu