ToolsCalculators
Urine anion gap
Distinguishes renal from GI causes of normal-anion-gap metabolic acidosis.
Urine anion gap
Urine sodium
mEq/L
Urine potassium
mEq/L
Urine chloride
mEq/L
Complete the fields above to see the result.
When to use
- Evaluating a normal-anion-gap (hyperchloraemic) metabolic acidosis to separate renal tubular acidosis from gastrointestinal bicarbonate loss.
Formula
Urine anion gap = urine Na⁺ + urine K⁺ − urine Cl⁻. A useful mnemonic: a neGUTive gap points to the gut (diarrhoea).
Pearls and pitfalls
- The gap is an indirect estimate of urinary ammonium; it is unreliable when the urine contains other unmeasured anions (e.g. ketones, hippurate in toluene toxicity).