Sodium Correction Calculator

When blood glucose levels spike, osmotic pressure shifts water from the intracellular space into the extracellular fluid. This osmotic fluid shift dilutes the concentration of sodium in the blood, causing pseudohyponatremia—a falsely lowered sodium reading even though total body sodium may be normal or high. To uncover the true electrolyte status, clinicians use mathematical adjustments. The standard formula adds 0.024 mEq/L of sodium for every mg/dL of glucose above normal (100 mg/dL): Corrected Na = Patient Na + 0.024 * (Serum Glucose - 100). Alternatively, the Katz formula applies a factor of 0.016: Corrected Na Katz = Patient Na + 0.016 * (Serum Glucose - 100), which is often favored in severe hyperglycemia.

Consider a patient admitted to the emergency department with severe hyperglycemia. Their measured serum sodium level is 128 mEq/L, and their lab results show a serum glucose level of 500 mg/dL. To find the true corrected sodium using the standard formula, we first determine how much glucose exceeds the baseline of 100 mg/dL: 500 - 100 = 400 mg/dL. Next, we multiply this excess by the standard correction factor of 0.024: 400 * 0.024 = 9.6. Finally, we add this value to the measured sodium: 128 + 9.6 = 137.6 mEq/L. Thus, the true corrected sodium level is approximately 138 mEq/L, revealing that the patient's hyponatremia is largely a dilutional artifact of high blood sugar.

Always use concurrent blood glucose and sodium panels drawn from the same blood sample to ensure accuracy. Remember that correction formulas are estimates; severe hypertriglyceridemia or hyperproteinemia can also interfere with sodium measurements and require separate adjustments. Never aggressively treat presumed hyponatremia without calculating corrected sodium first, as lowering blood sugar alone will naturally restore serum sodium levels.