Correct serum sodium for high blood glucose with the Katz formula, and estimate how one litre of IV fluid would move sodium using the Adrogué–Madias equation.
Result
How to use this tool
Enter the measured (uncorrected) serum sodium in mmol/L.
Enter the blood glucose in mg/dL from the same blood draw.
Enter body weight and sex so total body water can be estimated.
Read the corrected sodium and, under Advanced options, the estimated sodium change per litre of your chosen fluid.
Formula & worked example
Sodium 130 mmol/L with glucose 600 mg/dL corrects to 130 + 1.6 x (600 – 100) / 100 = 138 mmol/L.
Limitations — read this before you rely on it
Uses the Katz 1.6 factor and the Adrogué–Madias equation, both simplifications; real sodium also depends on potassium, urea, ongoing losses and kidney handling. The 1.6 factor is debated (some use 2.4 at very high glucose). This tool is for education only and is not medical advice. Talk to a clinician about any result that worries you, and never change treatment because of a calculator result.
Frequently asked questions
High glucose pulls water into the bloodstream and dilutes sodium, so the measured value understates the true sodium. The correction estimates what sodium would be at normal glucose.
Add 1.6 mmol/L to measured sodium for every 100 mg/dL of glucose above 100 mg/dL. It applies to hyperglycemia, not to low glucose.
It estimates how much serum sodium changes after one litre of a fluid, from (infusate sodium – serum sodium) / (total body water + 1). It is a planning estimate, not a prescription.
Total body water averages about 60% of body weight in men and 50% in women, so the same litre of fluid moves sodium slightly less in a larger water volume.
No. Correction speed matters: over-rapid sodium correction can cause osmotic demyelination. Rates are a clinician decision.