Urine Electrolytes

General Information

This test measures both urinary sodium and urinary potassium.

Urinary sodium, together with assessment of volume status, is useful in the differential diagnosis of hyponatramia. Urinary sodium levels are also frequently ordered during the workup of acute renal failure with the fractional excretion of sodium used as an important marker in distinguishing pre-renal from post-renal failure.

Urinary potassium may be ordered in the workup of hypokalemia. In case of GI loss of potassium, the urine potassium will be low. In case of renal loss of potassium, the urine potassium levels will be high. Decreased levels of urine potassium are also seen in hypoaldosteronism and adrenal insufficiency.