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Corrected Sodium for Glucose Calculator

Enter measured sodium and glucose to estimate corrected sodium.

How it is calculated

The tool adds a fixed correction to the measured sodium: correction = 1.6 × (glucose − 100) ÷ 100 and corrected Na = measured Na + correction. Sodium is in mEq/L (the same number as mmol/L) and glucose is in mg/dL. The reference point is 100 mg/dL, and the factor is always 1.6 per 100 mg/dL; the tool does not switch to another factor at very high glucose.

Both values must be above zero. The corrected sodium and the correction are rounded to one decimal, and the correction is shown with a plus sign when it is zero or positive. If glucose is below 100 mg/dL the correction is negative, so the corrected value comes out slightly lower than the measured one. This is an estimate for interpreting a lab result, not medical advice.

Worked example

A lab reports sodium 128 mEq/L with glucose 600 mg/dL.

Glucose above the 100 mg/dL reference: 600 − 100 = 500. Divided by 100 this is 5. Multiplying by 1.6 gives a correction of +8.0 mEq/L. Corrected sodium = 128 + 8.0 = 136.0 mEq/L. So most of the apparent low sodium is explained by the high glucose.

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Common mistakes

  • Entering glucose in mmol/L. The formula expects mg/dL, so 33.3 mmol/L must be converted to about 600 mg/dL first; typing 33 produces a small negative correction.
  • Typing the corrected value back in as the measured sodium, which corrects it twice.
  • Expecting the correction to matter at normal glucose. At 100 to 120 mg/dL it changes sodium by well under 1 mEq/L.
  • Using the result as a diagnosis. It is a single-factor estimate; a normal corrected value does not replace clinical assessment.
  • Mixing units for sodium. Use mEq/L or the equal mmol/L figure, not mg/dL.

Sources

About this calculator

High blood glucose pulls water osmotically out of cells and into the bloodstream, which dilutes serum sodium and can make a patient's measured sodium look falsely low even when their total body sodium is normal — a phenomenon called translocational or dilutional hyponatremia. The Katz formula corrects for this: corrected Na = measured Na + 1.6 × ((glucose − 100) / 100), adding back roughly 1.6 mEq/L of sodium for every 100 mg/dL of glucose above normal.

Without this correction, a hyperglycemic patient's true sodium status can be misjudged, leading to unnecessary workup for hyponatremia or, conversely, missing a real sodium disturbance that's masked by the glucose effect. Emergency physicians, internists, and endocrinologists use the Katz correction when interpreting labs in patients with significant hyperglycemia, such as those presenting with diabetic ketoacidosis or hyperosmolar hyperglycemic state. A later study (Hillier et al., 1999) measured about 2.4 mEq/L per 100 mg/dL, and more above 400 mg/dL, so many clinicians use 2.4 instead; the Katz factor of 1.6 used here can understate the corrected sodium when glucose is very high.

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Comments (1)

  • Editorial team

    The correction depends on glucose alone: at 600 mg/dL it adds 8.0 mEq/L to any measured sodium, so 128 becomes 136.0. A corrected value that stays low points to a sodium problem glucose does not explain, which belongs with the treating clinician. The tool applies a flat 1.6 factor, while some clinicians prefer 2.4 once glucose is very high. Which factor does your unit follow?

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