Corrected Sodium in Hyperglycemia

Corrected sodium is an essential clinical calculation used to estimate the true serum sodium level in the presence of significant hyperglycemia. When blood glucose levels are high, plasma osmolality increases, causing an osmotic shift of water from the intracellular space to the extracellular space (the plasma). This water influx dilutes the measured sodium concentration in the serum, leading to a condition known as dilutional hyponatremia or pseudohyponatremia. The measured lab value, therefore, does not accurately reflect the total body sodium. The correction formula, most commonly the Hillier-Katz formula, adjusts the measured sodium upward, typically adding 1.6 mEq/L to the sodium value for every 100 mg/dL that glucose is above the normal value of 100 mg/dL. This calculation is crucial for patient management as it prevents the unnecessary and potentially dangerous treatment of hyponatremia (such as administering hypertonic saline), indicating that the correct therapy is to focus on lowering glucose, which will naturally correct the sodium level as water shifts back into the cells.