Sodium Correction Calculator

The Sodium Correction Calculator adjusts measured serum sodium for the dilutional effect of hyperglycemia. In hyperglycemic states such as diabetic ketoacidosis (DKA) and hyperosmolar hyperglycemic state (HHS), elevated glucose acts as an effective osmole that draws water from the intracellular space into the extracellular space, diluting sodium and other electrolytes. The measured sodium therefore underestimates the patient's true sodium status. Corrected sodium estimates what the sodium level would be once glucose returns to normal.

The correction formula uses the Katz correction factor: Corrected Na = Measured Na + 1.6 x [(Glucose - 100) / 100]. For every 100 mg/dL increase in glucose above 100 mg/dL, sodium decreases by approximately 1.6 mEq/L due to osmotic water shift. This means a patient with a glucose of 600 mg/dL has a sodium approximately 8 mEq/L lower than their true sodium. A measured sodium of 128 in this context would correct to 136, revealing eunatremia rather than true hyponatremia.

Some experts recommend using a correction factor of 2.4 mEq/L per 100 mg/dL increase in glucose (the Hillier modification), particularly at very high glucose levels above 400 mg/dL. Studies suggest that the relationship between glucose and sodium may not be strictly linear, with the dilutional effect increasing proportionally more at higher glucose levels. The traditional 1.6 factor, however, remains the most widely used and cited in major textbooks and guidelines. This calculator uses the 1.6 factor as the standard approach.

The clinical importance of corrected sodium is paramount in DKA and HHS management. As insulin therapy lowers glucose, water shifts back into the intracellular space, and the measured sodium should rise. If the corrected sodium is normal or elevated, the measured sodium is expected to increase appropriately with treatment. If the corrected sodium is truly low (indicating both hyperglycemia-related dilution and true hyponatremia from excessive free water intake or SIADH), the sodium may not rise adequately with insulin treatment alone, and fluid management must be adjusted accordingly.

Monitoring the corrected sodium during DKA treatment is critical for guiding IV fluid selection. If the corrected sodium is normal or elevated, half-normal saline (0.45% NaCl) is typically appropriate after initial volume resuscitation. If the corrected sodium is low, normal saline (0.9% NaCl) should be continued to avoid excessively rapid sodium correction. The rate of sodium correction should not exceed 8-10 mEq/L in any 24-hour period to prevent osmotic demyelination syndrome (central pontine myelinolysis).

The corrected sodium also has prognostic value in hyperglycemic emergencies. A very high corrected sodium (above 150) suggests severe dehydration with significant free water deficit, typical of HHS. A normal or low corrected sodium is more common in DKA, where the duration of illness is typically shorter and dehydration less severe. The corrected sodium at presentation correlates with the degree of total body water deficit and guides the aggressiveness of fluid replacement therapy.