Hyperglycemia causes osmotic water shift into the extracellular space, diluting serum sodium. Corrected sodium reflects the true sodium concentration after glucose normalization. Two formulas are available: Katz (1973) and Hillier (1999), with Hillier preferred for glucose >400 mg/dL.
Katz Corrected Na
Hillier Corrected Na
Measured Na:
Recommendation:
Classification:
Note: Glucose >400 mg/dL — Hillier formula (2.4 correction factor) is more accurate for severe hyperglycemia as seen in DKA/HHS.
Formula
Katz: Corrected Na = Measured Na + 1.6 × [(Glucose − 100) / 100] Hillier: Corrected Na = Measured Na + 2.4 × [(Glucose − 100) / 100] For Glucose >400 mg/dL: Hillier formula preferred
Reference
Condition
Sodium
Notes
Hyponatremia
<136 mEq/L
Evaluate cause
Normal
136–145 mEq/L
—
Hypernatremia
>145 mEq/L
Free water deficit
Clinical Notes
In DKA and HHS, sodium is diluted by osmotic water shift from hyperglycemia. Corrected sodium reflects the true sodium concentration that would exist after glucose normalization. A rising corrected sodium in DKA indicates appropriate osmotic response; persistently low corrected Na may indicate a separate hyponatremia etiology. Management of DKA/HHS targets fluid resuscitation and insulin therapy to normalize glucose and sodium together.
For educational use only. Clinical decisions must incorporate full patient evaluation.
