Calculator

Sodium Correction Calculator

Corrects measured serum sodium for the dilutional effect of a high glucose.

Corrected sodium

135.0mEq/L

Within the normal range of 135–145 mEq/L.

Patient values

Measured sodium

mEq/L

The sodium printed on the lab report.

Blood glucose

The correction only matters once glucose is well above 100 mg/dL.

Try an example

Working

Measured sodium135.0mEq/L

Glucose (converted)100mg/dL

Correction applied+0.0mEq/L

Normal sodium135 – 145mEq/L

Normal fasting glucose70 – 100mg/dL

Corrected Na = measured Na + 0.016 × (glucose in mg/dL − 100)

For every 100 mg/dL the glucose sits above normal, the measured sodium reads about 1.6 mEq/L lower than the patient's true sodium. The formula simply adds that back.

A commonly taught alternative uses 0.024 rather than 0.016, based on work by Hillier, and is argued to be more accurate once glucose exceeds 400 mg/dL. This calculator uses the classic Katz factor of 0.016; expect a slightly larger correction if your institution prefers Hillier's.

Common questions

Glucose is osmotically active and does not cross cell membranes freely without insulin. A high plasma glucose therefore draws water out of cells into the plasma, and that extra water dilutes the sodium already there. No sodium has been lost — it is simply spread through more water.

0.016 is the original Katz factor and the one most references still quote; this calculator uses it. Hillier's experimental work suggests 0.024 fits better, especially above 400 mg/dL. Follow your local protocol, and be aware the two can differ by several mEq/L in severe hyperglycaemia.

That pattern points to dilutional hyponatraemia caused by the glucose rather than a sodium deficit. Treating the hyperglycaemia will usually bring the measured sodium up on its own — which is why the sodium often rises during insulin therapy and should be watched rather than chased.

Then there is a genuine hyponatraemia on top of the hyperglycaemia, and it needs its own workup — volume status, urine osmolality, urine sodium and a medication review. Correction tells you the question is real; it does not tell you the cause.

No. Pseudohyponatraemia is a laboratory artefact from very high lipids or proteins displacing plasma water, and it is unrelated to glucose. This correction will not fix it — a direct ion-selective electrode measurement will.

About this calculator

A high blood glucose pulls water out of cells into the bloodstream. The extra water dilutes the sodium, so the lab reports a low sodium in a patient who has no sodium deficit at all. This is translocational (dilutional) hyponatraemia.

Correcting the sodium answers the question that actually matters: is this patient genuinely short of sodium, or does the number simply reflect their glucose?

Use it when

Diabetic ketoacidosis or a hyperosmolar hyperglycaemic state

Any hyponatraemia found alongside a glucose above 100 mg/dL

Before treating an apparent hyponatraemia in a diabetic patient

Tracking sodium as glucose falls during insulin therapy

Do not rely on it when

Hyponatraemia has a cause other than glucose — SIADH, diuretics, heart failure

Severe hyperlipidaemia or hyperproteinaemia (pseudohyponatraemia) is present

Deciding the rate of correction — that is a separate clinical judgement

The glucose is normal; the correction then does almost nothing

Katz MA, N Engl J Med 1973; Hillier TA et al., Am J Med 1999.

Prepared by the PharmaWallah student team. Verify results with your textbook or instructor. Report an error · Editorial policy