Urine sodium

Urine sodium is a measurement of the concentration of sodium in the urine.

The urine sodium is expressed as a concentration (such as millimoles per liter). The result must therefore be interpreted in the context of the degree of urine concentration present. Alternatively, the urine sodium can be standardized to the excretion of creatinine using a formula such as the fractional excretion of sodium (FENa).

Criteria for cerebral salt wasting included hyponatremia <135 mEq/L, and urine output > 4 L in 12 hours with urine sodium >40 mEq/L.