Sodium correction for hyperglycemia is a clinical calculation used to adjust measured serum sodium levels in patients with significantly elevated blood glucose. Hyperglycemia, especially in conditions such as diabetic ketoacidosis (DKA) or hyperosmolar hyperglycemic state (HHS), can lead to a dilutional decrease in serum sodium concentration due to the osmotic effect of glucose. This “pseudohyponatremia” does not reflect a true sodium deficit but rather a shift of water from the intracellular to extracellular compartment.

Correcting sodium in hyperglycemic states is essential because uncorrected sodium values can be misleading and may underestimate the actual plasma tonicity, leading to inappropriate fluid management.

Physiological Basis

Glucose is an osmotically active substance. When serum glucose rises above normal levels, it increases extracellular osmolality. This osmotic gradient pulls water out of cells, diluting extracellular sodium. As a result, measured sodium may appear artificially low. Correcting for this effect provides a better estimate of true sodium concentration and overall osmolality.

Correction Formula

The most commonly used correction is:

Corrected Na⁺ = Measured Na⁺ + [ (Glucose − 100) / 100 ] × 1.6

• Glucose is measured in mg/dL.
• 1.6 mEq/L is the correction factor per 100 mg/dL increase in glucose above 100.

Some studies suggest that at very high glucose levels (> 400 mg/dL), a higher correction factor (2.0–2.4 mEq/L per 100 mg/dL) may be more accurate.

Example Calculation

A patient presents with the following values: – Measured serum sodium = 130 mEq/L – Blood glucose = 500 mg/dL

Using the correction formula: Corrected Na⁺ = 130 + [ (500 − 100) / 100 ] × 1.6 = 130 + (4 × 1.6) = 130 + 6.4 = 136.4 mEq/L

In this case, the patient’s true sodium status is near-normal, even though the uncorrected value suggests hyponatremia.

Normal Ranges / Interpretation

Normal serum sodium ranges between 135 and 145 mEq/L. – Uncorrected sodium in hyperglycemia may appear below 135 mEq/L (pseudohyponatremia). – Corrected sodium helps differentiate true hyponatremia from dilutional effects.

Clinical Significance

Sodium correction for hyperglycemia has important clinical implications:

• Accurate diagnosis: Prevents misclassification of patients as hyponatremic when sodium levels are actually normal.
• Guides fluid therapy: Corrected sodium helps determine whether hypotonic or isotonic fluids are appropriate during DKA/HHS management.
• Prevents complications: Avoids overly rapid correction of sodium, which can lead to cerebral edema or osmotic demyelination syndrome (ODS).
• Improves osmolality assessment: True sodium is essential for accurate calculation of serum osmolality and effective osmolality.

Indications for Use

Sodium correction should be applied in:

• Patients with hyperglycemia (glucose > 200 mg/dL) and apparent hyponatremia.
• Management of diabetic ketoacidosis (DKA).
• Hyperosmolar hyperglycemic state (HHS) evaluations.
• Any acute illness with severe hyperglycemia where fluid therapy is being planned.

Limitations

While widely used, sodium correction has limitations:

• Variable correction factors: The commonly used 1.6 mEq/L factor may underestimate sodium at very high glucose levels.
• Individual variability: Patient-specific factors like renal function, hydration status, and chronicity of hyperglycemia can affect accuracy.
• Does not replace clinical judgment: Corrected sodium is an estimate and should always be interpreted alongside clinical and laboratory findings.