Corrected Sodium for Hyperglycaemia Calculator

Understanding the corrected sodium for hyperglycaemia calculator — concept and principle

Very high blood glucose pulls water out of cells into the bloodstream, which dilutes sodium and makes the measured value look low. The corrected sodium estimates what the sodium concentration would be once glucose returns to normal. It is used in diabetic ketoacidosis (DKA) and hyperosmolar hyperglycaemic state (HHS) to judge the true water balance and to choose and monitor intravenous fluids.

Every 100 mg/dL of glucose above 100 adds 2.4 (or 1.6) mmol/L back to the measured sodium.

How it is calculated

For every 100 mg/dL of glucose above 100 mg/dL, add a fixed amount to the measured sodium:

Hillier: corrected Na = Na + 0.024 × (glucose − 100), which is 2.4 mmol/L per 100 mg/dL.

Katz: corrected Na = Na + 0.016 × (glucose − 100), which is 1.6 mmol/L per 100 mg/dL.

Sodium in mmol/L, glucose in mg/dL (100 mg/dL ≈ 5.55 mmol/L).

The principle

Glucose cannot freely enter most cells without insulin, so when it accumulates in the blood it acts as an effective osmole and draws water out of cells. The extra water in the extracellular space lowers the sodium concentration even though total body sodium has not changed. This is called translocational hyponatraemia. Katz derived 1.6 from a theoretical model; Hillier and colleagues gave healthy volunteers infusions to raise glucose and measured a larger average fall, about 2.4 mmol/L per 100 mg/dL, with an even steeper effect above about 400 mg/dL.

Worked example

Glucose excess = 600 − 100 = 500 mg/dL.
Hillier: 0.024 × 500 = 12, so corrected Na = 130 + 12 = 142 mmol/L.
Katz: 0.016 × 500 = 8, so corrected Na = 130 + 8 = 138 mmol/L.
Although the measured sodium of 130 looks low, both corrected values are in or near the normal range. As glucose falls with treatment, sodium is expected to rise towards 138–142.

Each point is the calculator re-run with only “Measured sodium (mmol/L)” changed; the gold point is the default example. Change the inputs above and this chart follows your numbers.

Measured sodium (mmol/L)	Corrected Na (Hillier, 2.4)
32.5	44.5
65	77
97.5	109.5
130	142
162	174.5
195	207
260	272

How to read the result

Where does your result fall?

The normal range for sodium is about 135–145 mmol/L. A corrected value above 145 means the patient is genuinely short of free water, which is common in HHS. A corrected value below 135 points to true hyponatraemia in addition to the glucose effect. During treatment, a measured sodium that fails to rise as glucose falls may warrant a change in fluids.

Common mistakes

Confusing this with pseudohyponatraemia from very high lipids or proteins, which is a laboratory artefact.
Using glucose in mmol/L in a formula that expects mg/dL.
Treating the low measured sodium with hypertonic saline when the corrected value is normal.

Keep in mind: Corrected sodium is an estimate, not a diagnosis. The 1.6 and 2.4 factors are averages and individuals vary. Fluid management in DKA or HHS must be supervised by clinicians with frequent laboratory checks.

Frequently asked questions

Which correction factor should I use?

Many references now prefer 2.4 (Hillier), but both are shown so you can see the plausible range.

Why does sodium rise during DKA treatment?

As insulin moves glucose into cells, water follows, and the diluting effect disappears.

Is the corrected sodium the same as effective osmolality?

No. Effective osmolality is 2 × Na + glucose ÷ 18 and uses the measured sodium.

Sources: Hillier TA et al. Hyponatremia: evaluating the correction factor for hyperglycemia. Am J Med 1999. · Katz MA. Hyperglycemia-induced hyponatremia: calculation of expected serum sodium depression. N Engl J Med 1973.

Checked 8 Nov 2026. Hillier et al., Am J Med 1999; Katz, NEJM 1973.

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