About the Corrected Sodium Calculator
High blood glucose pulls water out of cells into the bloodstream, diluting the sodium that is already there. The measured sodium therefore reads lower than it "really" is — a translocational (hyperglycemic) hyponatremia. The corrected sodium estimates what the sodium concentration would be if glucose were normal, which helps clinicians judge true tonicity and water balance in diabetic ketoacidosis (DKA), hyperosmolar hyperglycemic state (HHS) and other severe hyperglycemia.
Two correction factors are in common use. Katz (1973) derived a fall of 1.6 mEq/L in sodium for every 100 mg/dL rise in glucose above 100 mg/dL from theory. Hillier and colleagues (1999) measured the effect experimentally in healthy volunteers and found an average fall of 2.4 mEq/L per 100 mg/dL, with a larger effect above 400 mg/dL. This calculator shows both and lets you choose which one drives the headline result.
Enter measured sodium and glucose from the same sample, in mg/dL or mmol/L. No correction is applied when glucose is 100 mg/dL (5.6 mmol/L) or lower. The calculator is for clinicians and students; it does not account for other causes of hyponatremia such as lipaemia, paraproteins, mannitol or water excess.
With the default inputs, the corrected sodium is 139.6 mEq/L. Change any value above to recalculate instantly.
How to use the corrected sodium calculator
- 1Enter the measured serum sodium.
- 2Choose glucose units and enter the glucose from the same sample.
- 3Pick the Hillier (2.4) or Katz (1.6) factor for the headline result.
- 4Compare the corrected sodium with the 135–145 mEq/L reference range.
Formula and method
For every 100 mg/dL that glucose rises above a normal reference of 100 mg/dL, water shifts out of cells and lowers serum sodium. The correction adds back k mEq/L per 100 mg/dL of excess glucose. Katz’s 1.6 factor was derived from a theoretical model of water redistribution; Hillier’s 2.4 factor was measured experimentally by raising glucose above 600 mg/dL in healthy volunteers.
Glucose in mmol/L is converted to mg/dL by multiplying by 18. If glucose is at or below 100 mg/dL the excess is taken as zero, so corrected sodium equals measured sodium.
- Na
- Serum sodium (mEq/L = mmol/L)
- k
- Correction factor in mEq/L per 100 mg/dL of glucose
- glucose
- Serum glucose (mg/dL)
Worked examples
DKA with apparent hyponatremia
Glucose 500 mg/dL is 400 above normal (4 × 100). Hillier adds 2.4 × 4 = 9.6, giving 139.6 mEq/L; Katz adds 1.6 × 4 = 6.4, giving 136.4. The low measured sodium of 130 is explained by hyperglycemia.
True hyponatremia persists
Glucose 300 mg/dL is 2 × 100 above normal. Katz adds 3.2 to give 128.2 mEq/L (Hillier: 129.8). Sodium is still low after correction, so hyperglycemia does not fully explain it.
Glucose in mmol/L
Glucose 30 mmol/L × 18 = 540 mg/dL, which is 4.4 × 100 above normal. Hillier adds 2.4 × 4.4 = 10.56 for 143.6 mEq/L; Katz adds 7.04 for 140.0 mEq/L.
Frequently asked questions
Which correction factor should I use, 1.6 or 2.4?+
Katz’s 1.6 factor is the traditional teaching value, but Hillier’s 1999 experimental study found an average of 2.4 mEq/L per 100 mg/dL and suggested it is the better overall estimate. Many references now prefer 2.4, especially when glucose exceeds 400 mg/dL.
Is hyperglycemic hyponatremia the same as pseudohyponatremia?+
Not exactly. Pseudohyponatremia is a lab artefact from very high lipids or proteins, with normal true sodium and osmolality. Hyperglycemia causes a real dilution of sodium by water drawn out of cells, with high serum osmolality — a translocational hyponatremia.
Why does corrected sodium matter in DKA and HHS?+
As insulin lowers glucose, water moves back into cells and measured sodium rises. The corrected sodium predicts where sodium will settle, helping clinicians spot hidden hypernatremia and monitor changes in tonicity during treatment.
What is the formula for corrected sodium?+
Corrected Na = measured Na + k × (glucose − 100) ÷ 100, with glucose in mg/dL and k = 1.6 (Katz) or 2.4 (Hillier). For glucose in mmol/L, multiply by 18 first, or use about 0.4 mEq/L per mmol/L above 5.6 (Hillier).
For healthcare professionals and education only. This calculator implements a published formula or score but is not a diagnosis and does not replace clinical judgment. Verify inputs and results against the original source before using them in patient care.