Corrected Sodium for Hyperglycemia Calculator

About

The corrected sodium formula accounts for the dilutional (factitious) lowering of measured serum sodium caused by hyperglycemia. When blood glucose is elevated, the increased extracellular osmolality draws water from the intracellular space into the vascular compartment, effectively diluting the sodium concentration. This phenomenon was first described by Katz in 1973, who proposed a correction factor of 1.6 mEq/L decrease in measured sodium per 100 mg/dL rise in glucose above 100 mg/dL. The formula is: Corrected Na = Measured Na + 1.6 × (Glucose − 100) / 100. This correction is essential for accurate assessment of true sodium status in hyperglycemic patients, particularly those with diabetic ketoacidosis (DKA) and hyperosmolar hyperglycemic state (HHS), where severe hyperglycemia can mask true hyponatremia, normonatremia, or even hypernatremia. In 1999, Hillier and colleagues re-evaluated the correction factor and confirmed that 1.6 is more accurate than the previously used 2.4 mEq/L factor, as the 2.4 factor overcorrects and may suggest hypernatremia where none exists. Clinicians must be aware that the corrected sodium reflects the sodium concentration that would exist if glucose were normal — this helps guide fluid therapy, avoiding both overly aggressive hypotonic fluid administration leading to iatrogenic hyponatremia, and insufficient free water replacement leading to persistent hypernatremia. The correction is recommended for all hyperglycemic patients with glucose >200 mg/dL. Evidence level: Grade B, supported by prospective physiological studies.

Formula

Corrected Na (mEq/L) = Measured Na + 1.6 × (Glucose - 100) / 100

The corrected sodium formula is: Corrected Na = Measured Na + 1.6 × (Glucose − 100) / 100. Each component is important: Measured Na is the actual laboratory value; Glucose is the current blood glucose in mg/dL; 100 represents the upper limit of normal glucose; 1.6 is the correction factor representing mEq/L decrease per 100 mg/dL glucose elevation. The formula is designed to be used when glucose exceeds 100 mg/dL, but in practice, the correction is only clinically meaningful when glucose >200 mg/dL. For example, a patient with measured Na 132 mEq/L and glucose 600 mg/dL: corrected Na = 132 + 1.6 × (600 − 100) / 100 = 132 + 1.6 × 500 / 100 = 132 + 1.6 × 5 = 132 + 8.0 = 140 mEq/L. This reveals that the apparent hyponatremia (132 mEq/L) was entirely due to hyperglycemia — the corrected value is normal. For a patient with measured Na 125 mEq/L and glucose 800 mg/dL: corrected Na = 125 + 1.6 × (800 − 100) / 100 = 125 + 1.6 × 7 = 125 + 11.2 = 136.2 mEq/L — still hyponatremic, indicating true sodium depletion. To interpret results: corrected Na <135 mEq/L indicates true hyponatremia requiring evaluation and management; corrected Na 135–145 mEq/L is normal; corrected Na >145 mEq/L indicates true hypernatremia. The correction should be recalculated as glucose improves during treatment. A falling corrected sodium during DKA treatment may indicate excessive hypotonic fluid administration. The formula assumes normal lipid and protein levels — severe hypertriglyceridemia or paraproteinemia can also cause factitious hyponatremia through a similar dilutional mechanism, but these require different correction approaches.

Score Interpretation

Correcting sodium for hyperglycemia is essential in the management of diabetic emergencies and has direct clinical implications. The American Diabetes Association (ADA) Standards of Medical Care recommend calculating corrected sodium in all patients presenting with DKA or HHS. In DKA, measured sodium is typically low due to hyperglycemia, but the corrected sodium often reveals the true sodium status. This guides fluid resuscitation decisions — using corrected rather than measured sodium prevents two common errors: (1) administering hypotonic fluids to a patient whose true sodium is normal, causing iatrogenic hyponatremia and cerebral edema risk, and (2) failing to recognize true hypernatremia, which requires free water replacement to prevent neurological complications. The ADA and Joint British Diabetes Societies (JBDS) guidelines explicitly recommend using corrected sodium to guide fluid therapy in DKA and HHS. As glucose falls during treatment, the corrected sodium will decrease — a rapidly falling corrected sodium signals excessive free water administration and should prompt adjustment of IV fluids. In HHS, where hyperglycemia is extreme (often >600 mg/dL), the corrected sodium is critical for calculating the free water deficit and choosing the appropriate replacement fluid (0.45% saline vs. 0.9% saline). The corrected sodium also helps in diagnosing the cause of hyponatremia in hyperglycemic patients — distinguishing between true hyponatremia requiring specific management versus pseudo-hyponatremia that will resolve with glucose control. The formula has also been applied in other hyperglycemic states such as post-operative stress hyperglycemia and parenteral nutrition-associated hyperglycemia. Beyond the 1.6 factor, alternative correction formulas exist — Katz (2.4) and expert consensus recommends 2.4 for DKA and 1.6 for HHS, though most guidelines now favor 1.6 for simplicity. Evidence level: Grade B, supported by consensus guidelines from ADA and JBDS.

Reference Ranges