Hypertonic hyponatremia is most often associated with which condition?

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Hypertonic hyponatremia occurs when serum osmolality is increased by another solute, causing water to move out of cells and dilute the plasma sodium. Glucose is the classic driver here: in significant hyperglycemia, high glucose raises plasma osmolality, pulling water into the extracellular space and lowering the measured sodium even though overall tonicity remains high. To interpret sodium correctly, you adjust for glucose—roughly, for every 100 mg/dL glucose above the normal level, the sodium concentration decreases by about 1.6–2.0 mEq/L, and the corrected Na may be closer to normal. Therefore, hyperglycemia is most often associated with hypertonic hyponatremia. Hyperlipidemia can cause pseudohyponatremia with some lab methods but does not create true hypertonicity; hyperkalemia and hypoglycemia do not elevate plasma osmolality in this way.