What does the 24-Hour Urinary Chloride Excretion test measure?

Why is 24-Hour Urinary Chloride Excretion measured?

Urinary chloride is the single most useful test for classifying metabolic alkalosis as chloride-responsive (volume-contracted states, where urine chloride falls below 20–25 mmol/L) or chloride-resistant (mineralocorticoid excess or severe hypokalaemia, where urine chloride remains elevated). It also aids evaluation of hypovolaemia, surreptitious diuretic or laxative use, and salt-wasting disorders. Because it reflects both dietary intake and renal tubular handling, urinary chloride is interpreted alongside serum electrolytes, acid–base status, and volume assessment rather than in isolation.

Reference ranges

Standard reference

Approximately 110–250 mmol/24 h in adults on a typical Western diet; intake-dependent and laboratory-specific.

Functional medicine optimal

Normal excretion mirrors dietary intake; in the evaluation of metabolic alkalosis, a spot or 24-hour urine chloride below 20–25 mmol/L indicates volume depletion and chloride responsiveness.

Units

mmol/24h, mEq/24h

Reference ranges vary by laboratory and assay platform. Interpret in context of the issuing laboratory's stated range.