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Omnikalc

Corrected sodium calculator for high blood sugar

Correct a measured sodium level for high blood glucose with the Katz (1.6) and Hillier (2.4) formulas, as used in diabetic ketoacidosis and hyperosmolar states.

Updated on
Your inputs
mmol/L

Value out of range

Value out of range

Results

Corrected sodium, Hillier (2.4 per 100 mg/dL)

142.0 mmol/L

Within the usual 135 to 145 range
Corrected sodium, Katz (1.6 per 100 mg/dL)
138.0 mmol/L
Glucose in mmol/L
33.3 mmol/L

Why sodium needs correcting

When blood sugar is very high, as in diabetic ketoacidosis or the hyperosmolar hyperglycemic state, glucose pulls water out of cells into the bloodstream. That extra water dilutes sodium, so the lab result looks lower than the body’s true water balance. As insulin brings glucose down, water moves back into cells and sodium rises.

The corrected sodium predicts where sodium will land once glucose is normal. It helps choose fluids and spot hidden dehydration.

The two formulas

With glucose in mg/dL:

  • Katz (1973): corrected Na = Na + 1.6 × (glucose − 100) ÷ 100
  • Hillier (1999): corrected Na = Na + 2.4 × (glucose − 100) ÷ 100

Katz derived his factor from theory. Hillier measured it in healthy volunteers given a glucose load and found 2.4 fits better, especially above about 400 mg/dL. Many references show both.

Worked example

Measured sodium 130 mmol/L, glucose 600 mg/dL:

  1. Glucose above the reference: 600 − 100 = 500 mg/dL.
  2. Katz: 130 + 1.6 × 5 = 138.0 mmol/L.
  3. Hillier: 130 + 2.4 × 5 = 142.0 mmol/L.

A sodium that looked low is in fact normal or slightly high once corrected. The patient is not truly hyponatremic and may be short of free water.

Reading the result

Corrected sodium Meaning
below 135 true hyponatremia
135 to 145 normal range
above 145 hypernatremia, free water deficit likely

If the corrected value is high, see the free water deficit calculator to estimate how much water is missing.

Units

Glucose in mmol/L is multiplied by 18 to get mg/dL: 33.3 mmol/L equals 600 mg/dL. The calculator’s unit selector does this for you.

Limits

The correction assumes glucose is the only extra solute. Mannitol, contrast dye or very high lipids or proteins (pseudohyponatremia with some lab methods) can also affect the result. Sodium should be checked often during treatment instead of relying on a single prediction.

This calculator is for general information and education. It is not medical advice and does not replace the judgment of a doctor, nurse or pharmacist who knows the full clinical picture.

Frequently asked questions

Why correct sodium for high blood sugar?

High glucose draws water out of cells into the blood, which dilutes sodium. The measured sodium then looks lower than it will be once glucose comes down. The corrected value shows the true water balance.

What is the corrected sodium formula?

Katz: sodium + 1.6 × (glucose − 100) ÷ 100. Hillier: sodium + 2.4 × (glucose − 100) ÷ 100, with glucose in mg/dL. With 130 mmol/L and 600 mg/dL, the result is 138 with Katz and 142 with Hillier.

Which correction factor should I use, 1.6 or 2.4?

Hillier's 2.4 factor comes from a study in volunteers and is closer to observed values when glucose is above about 400 mg/dL. Many references show both. The calculator highlights the Hillier result.

Does the correction apply in mmol/L?

Yes. Convert glucose to mg/dL by multiplying mmol/L by 18, or let the calculator do it with the unit selector. 5.6 mmol/L corresponds to the 100 mg/dL reference.

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Results are estimates provided for information purposes. They do not replace professional advice.

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