How it's calculated
Corrected sodium = measured sodium + 1.6 mmol/L for every 100 mg/dL that glucose is above 100 mg/dL (the classic Katz correction factor). High glucose pulls water into the vascular space, diluting sodium and making the measured value look artificially low.
Correction factors in use
| Source | Correction factor |
|---|---|
| Katz (1973) — used here | 1.6 mmol/L per 100 mg/dL glucose above 100 |
| Hillier (1999) — revised | 2.4 mmol/L per 100 mg/dL glucose above 100 |
Clinical use
- Correcting for hyperglycaemia reveals whether a patient's true sodium status is normal, low, or high — a measured sodium that looks low in the context of severe hyperglycaemia (e.g. DKA/HHS) may actually be normal once corrected.
- This matters for both diagnosis (differentiating true hyponatraemia from a dilutional effect of hyperglycaemia) and for guiding fluid/electrolyte management as glucose is corrected.
- As glucose falls with treatment (e.g. of DKA), corrected sodium should be expected to approach the measured value — trend both together rather than reacting to a single corrected value in isolation.
- The Hillier correction factor (2.4) gives a higher corrected value than the classic Katz factor (1.6) — the true relationship is not perfectly linear across all glucose ranges, so either is a reasonable clinical estimate.
Frequently asked questions
Why does high blood sugar affect sodium readings?
High glucose draws water from inside cells into the bloodstream by osmosis, diluting the measured sodium concentration — the corrected sodium calculation estimates what the sodium would be if glucose were normal, revealing the true sodium status.
What correction factor does this calculator use?
It uses the classic Katz correction factor of 1.6 mmol/L sodium increase for every 100 mg/dL that glucose is above 100 mg/dL — a revised factor of 2.4 (Hillier) is also used by some, giving a slightly higher corrected value.
Why does corrected sodium matter in diabetic ketoacidosis (DKA)?
Patients in DKA often have very high glucose, which can make a measured low sodium look more concerning than it truly is — correcting for the glucose effect helps clarify whether there's a genuine sodium deficit needing separate attention, alongside standard DKA fluid and insulin management.
Should I trend corrected sodium or measured sodium during treatment?
Both are useful — as glucose falls with treatment, the corrected and measured values should converge; tracking this trend helps confirm that fluid and electrolyte management is proceeding as expected.
References
- Katz MA. Hyperglycemia-induced hyponatremia — calculation of expected serum sodium depression. N Engl J Med. 1973;289:843-844.
- Hillier TA, et al. Hyponatremia: evaluating the correction factor for hyperglycemia. Am J Med. 1999;106:399-403.
- Kitabchi AE, et al. Hyperglycemic crises in adult patients with diabetes. Diabetes Care. 2009;32:1335-1343.