What is corrected sodium?

Corrected sodium is the estimated true serum sodium value adjusted for the dilutional effect of hyperglycemia. High blood glucose draws water out of cells, diluting the sodium concentration. Corrected sodium tells you what the sodium would be if glucose were at a normal level (~100 mg/dL).

Which formula should I use — Katz or Hillier?

The Katz formula (1.6 mEq/L per 100 mg/dL) is the classic, widely taught correction. The Hillier formula (2.4 mEq/L per 100 mg/dL) was derived from a larger study and is considered more accurate when glucose is very high (above 400 mg/dL). Many clinicians now prefer Hillier or report both values.

What is the normal glucose baseline used?

The standard baseline is 100 mg/dL (5.6 mmol/L), representing the upper end of the normal fasting glucose range. Only glucose above this threshold is used in the correction calculation.

What if my glucose is below 100 mg/dL?

If the measured glucose is at or below 100 mg/dL, no correction is needed and the corrected sodium equals the measured sodium. The calculator will indicate this automatically.

Can I enter glucose in mmol/L?

This calculator uses mg/dL for glucose input. To convert mmol/L to mg/dL, multiply by 18. For example, 20 mmol/L = 360 mg/dL.

Is this tool a substitute for clinical judgment?

No. This calculator is an educational and clinical reference aid only. Always interpret results in the full clinical context and consult current clinical guidelines or a specialist when making treatment decisions.

Corrected Sodium Calculator

Enter measured sodium and glucose to get corrected serum sodium using the Katz and Hillier formulas.

Patient Values

Measured Serum Sodium

mEq/L

Normal range: 135–145 mEq/L

Concurrent Serum Glucose

mg/dL

Must be above 100 mg/dL for correction to apply

Formulas Used

Katz (1.6): Corrected Na = Measured Na + 1.6 × [(Glucose − 100) / 100]

Hillier (2.4): Corrected Na = Measured Na + 2.4 × [(Glucose − 100) / 100]

Enter patient values and click Calculate

Summary

In hyperglycemia, high blood glucose causes osmotic fluid shifts from intracellular to extracellular space, diluting serum sodium and causing pseudohyponatremia. The corrected sodium calculator adjusts the measured sodium value to reflect what it would be at a normal glucose level. Two widely used formulas exist: the Katz formula (adds 1.6 mEq/L per 100 mg/dL glucose above normal) and the Hillier formula (adds 2.4 mEq/L per 100 mg/dL), with Hillier considered more accurate at very high glucose levels.

How it works

Enter the measured (reported) serum sodium in mEq/L.
Enter the concurrent serum glucose in mg/dL.
The calculator subtracts the normal glucose baseline (100 mg/dL) from the measured glucose.
The glucose excess is divided by 100 and multiplied by the correction factor (1.6 for Katz, 2.4 for Hillier).
The result is added to the measured sodium to produce the corrected sodium value.
Both formula results are displayed side by side for clinical comparison.

Use cases

Evaluate true sodium status in diabetic ketoacidosis (DKA).
Assess sodium in hyperglycemic hyperosmolar state (HHS).
Distinguish true hyponatremia from dilutional pseudohyponatremia.
Guide fluid and electrolyte management in critically ill patients.
Teaching medical students and residents about osmolar correction.
Quick bedside reference for emergency department providers.
Compare Katz vs. Hillier results when glucose exceeds 400 mg/dL.
Evaluate sodium before and after insulin therapy in DKA.

Frequently Asked Questions

Last updated: 2026-09-30 · Reviewed by Nham Vu