For healthcare professionals
Corrected Sodium Calculator
High blood glucose draws water out of cells into the blood, which lowers the measured sodium. When the glucose comes down, the sodium rises again. Correction formulas estimate what the sodium would be at a normal glucose. This tool shows the two common ones, Katz and Hillier, side by side. It is written for clinicians and is not a diagnosis.
Laboratory values
Use sodium and glucose from the same blood sample. Nothing you enter leaves this page.
What you will see
The sodium corrected by the Katz and by the Hillier formula, with the working.
Educational only, not medical advice. Not a diagnosis. Decisions belong to the treating team.
Source
The Katz and Hillier formulas and the 5.6 mmol/L (100 mg/dL) baseline as printed by Broman ME and colleagues, PLOS ONE 2026, an open-access (CC BY) study. The tests check both formulas against the differences the authors report at a glucose of 60 mmol/L, one step above baseline in each unit, no correction at or below baseline, and the input limits.
Validated in
Broman 2026 applied both formulas to 297,714 paired sodium and glucose results from 9,863 adults in intensive care in Sweden. Hillier's factor came from a study of six young, healthy volunteers, as described by Broman 2026.
Limits
Both formulas model a mostly closed system. Critically ill patients have changing fluid balance, kidney losses and sodium given in fluids, so the real change in sodium can differ. Glucose above 25 mmol/L was measured with an accuracy of plus or minus 1 mmol/L in the study cohort. The formulas disagree more as glucose rises, by 7.8 mmol/L at a glucose of 60 mmol/L.
The formulas
With glucose in mmol/L (Broman 2026):
- Katz: corrected sodium = measured sodium + 1.6 x (glucose - 5.6) / 5.6.
- Hillier: corrected sodium = measured sodium + 2.4 x (glucose - 5.6) / 5.6.
Both assume a baseline glucose of 5.6 mmol/L (100 mg/dL), below which no correction is applied (Broman 2026). With glucose in mg/dL, the tool uses the same factors per 100 mg/dL above 100 mg/dL. Hillier found that a factor of 2.4 best models the sodium fall when glucose is above 24 mmol/L (400 mg/dL) (Broman 2026).
Worked example: a measured sodium of 130 mmol/L with a glucose of 60 mmol/L gives 130 + 1.6 x (60 - 5.6) / 5.6 = 145.5 mmol/L by Katz and 130 + 2.4 x (60 - 5.6) / 5.6 = 153.3 mmol/L by Hillier, a difference of 7.8 mmol/L.
What the study found
In the Swedish intensive care cohort, 95.3% of glucose results were above the baseline and so implied a correction. Correcting sodium did not change the adjusted intensive care mortality. But 6.1% of patients had a sodium shift of more than 8 mmol/L in 24 hours, and without correction for glucose about 5% (Katz) to 9% (Hillier) of those patients would have been missed. A largest 24-hour sodium shift as small as 4.00 to 5.99 mmol/L was linked with higher intensive care mortality (Broman 2026).
Related tools
For a high sodium, the free water deficit calculator estimates the missing water. Glucose and sodium also enter the serum osmolality calculator. The sodium infusate calculator (Adrogue-Madias) estimates how one litre of a chosen fluid changes the sodium. For a metabolic acidosis, see the anion gap calculator. Other bedside scores are listed under For healthcare professionals.
Sources
- Broman ME, Forsal I, Silambanan S. Mathematical analysis of the relationship between glucose and sodium in a large Swedish cohort of critically ill patients. PLoS One. 2026;21:e0360072. doi:10.1371/journal.pone.0360072. PMID 42905668. Open access (CC BY). Introduction, Equations 1 and 2 (Katz 1.6 and Hillier 2.4 corrections; 5.6 mmol/L baseline), Results and Abstract (9,863 ICU patients; sodium shifts). pmc.ncbi.nlm.nih.gov/articles/PMC13686479/
Written and maintained by the uncovermyrisk.com editorial team. We do not have a medical reviewer; every claim links to its primary source above. Last reviewed: 2026-11-02. Spotted an error? See About.