Sodium is a key electrolyte that regulates fluid balance, nerve conduction, and muscle function.

The kidneys play a central role in sodium excretion and conservation.

Measuring sodium in a spot urine sample helps assess renal handling of sodium and overall electrolyte status.

Clinical uses include:

Differentiating causes of hyponatremia (renal vs. extrarenal losses).

Evaluating volume status in patients with dehydration, edema, or heart failure.

Monitoring renal tubular function.

Assessing response to diuretics or fluid therapy.

Often performed alongside serum sodium, urine osmolality, and creatinine for comprehensive evaluation.

Analyte: Sodium in urine (mmol/L).

Normal Range (varies by lab): ~40–220 mmol/L in random samples (values depend on diet and hydration).

Abnormal Findings:

Low urine sodium (<20 mmol/L): Suggests extrarenal sodium loss (vomiting, diarrhea) or volume depletion.

High urine sodium (>40 mmol/L): Suggests renal sodium loss (renal disease, diuretics, adrenal insufficiency).

Clinical Use:

Provides a marker of renal sodium handling and electrolyte balance.

Helps guide diagnosis and management of hyponatremia, edema, and renal disorders.

Supports nephrology and internal medicine evaluations.