Calculate the glucose-corrected serum sodium to reveal true body tonicity in hyperglycemia. Classic Katz (1973) formula Na_corr = Na + 1.6 × (Glucose − 100)/100 (glucose mg/dL), or Hillier (1999) Na_corr = Na + 2.4 × (Glucose − 100)/100 which is more accurate at very high glucose (Katz tends to underestimate). Glucose unit selectable: mg/dL or mmol/L (reference 5.5 mmol/L). Hyperglycemia shifts water extracellularly and dilutes sodium; the corrected value reflects the real water balance. Corrected Na < 135 indicates true hyponatremia (DKA/HHS with free-water excess, SIADH, GI/renal losses); > 145 indicates true hypernatremia (common in HHS, signals free-water deficit and guides replacement). Derived from Katz NEJM 1973, Hillier 1999, Adrogué NEJM 2000, and MDCalc. Not medical advice.
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Key facts
Category
Health
Input types
select, number
Output type
json
Sample coverage
4
API ready
Yes
Overview
The Corrected Sodium (Glucose) Calculator estimates serum sodium after accounting for the diluting effect of hyperglycemia. Enter measured sodium, glucose, glucose units, and a correction factor using either the Katz 1.6 or Hillier 2.4 formula.
When to use
When serum glucose is elevated and the measured sodium may be diluted by hyperglycemia.
When assessing sodium status in clinical contexts such as DKA or HHS.
When comparing Katz and Hillier correction methods, especially with very high glucose.
How it works
1Enter measured serum sodium in mmol/L and serum glucose.
2Select glucose units: mg/dL or mmol/L.
3Choose the Katz 1.6 or Hillier 2.4 correction factor.
4The calculator returns corrected sodium in mmol/L, rounded to the selected number of decimal places, with a category.
Use cases
Reviewing sodium results in patients with marked hyperglycemia.
Supporting electrolyte assessment during DKA or HHS evaluation.
Teaching or checking the difference between Katz and Hillier sodium corrections.
Examples
1. HHS sodium assessment with the Katz formula
Clinician or medical student
Background
A patient has measured sodium of 128 mmol/L and glucose of 600 mg/dL during a hyperglycemic presentation.
Problem
Determine whether the low measured sodium remains low after correcting for hyperglycemia.
How to use
Enter sodium 128, glucose 600, select mg/dL, choose Katz 1.6, and set decimal places to 1.