Urine electrolytes assays are typically employed to resolve in-patient hyponatraemia diagnoses. A urinary sodium <20 mmol/L is consistent with a dehydrated patient with functional renal tubules who will respond to rehydration, while a urinary sodium >20 mmol/L (typically >50 mmol/L), in conjunction with a low/normal urea and/or urate, may be indicative of SIADH.
No reference range
|Sample & container required||Random urine (preferred) or 24 hour urine collection|
|Sample volume||Random urine: 0.5 mL or 24 hour urine collection|
|Turnaround time||Random urine: 1 day 24 hour urine collection: 2 days|