Urine Sodium Test

This test measures the concentration of sodium (Na⁺) in urine, indicating how well the renal tubules are handling the reabsorption and excretion of this essential ion. Urine sodium excretion depends on the balance between dietary intake, extracellular fluid volume, and levels of regulatory hormones (such as aldosterone and atrial natriuretic peptide - ANP). It is often ordered along with serum sodium (Serum Na) to evaluate the cause of any abnormalities in its levels (hyponatremia or hypernatremia) and to differentiate between renal (kidney-related) and non-renal causes.