UAG assumes that chloride is the only significant unmeasured anion in urine. Ketones or drugs can affect the gap.
About this calculator
Overview
The Urine Anion Gap (UAG) is used to estimate the concentration of ammonium (NH₄⁺) in the urine. It is primarily used to differentiate between renal and extrarenal (usually gastrointestinal) causes of hyperchloremic (normal anion gap) metabolic acidosis.
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Pro Tips
UAG is only useful in the setting of normal anion gap metabolic acidosis.
A 'negative' UAG is typically less than -20 mmol/L.
D-lactic acidosis and other unmeasured anions can interfere with UAG accuracy.
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Fun Facts
"In metabolic acidosis, healthy kidneys should increase ammonium excretion to remove acid."
"Ammonium (NH₄⁺) is a cation that is excreted with chloride (Cl⁻)."
"A negative UAG indicates high ammonium excretion (typical for diarrhea)."
"A positive UAG indicates low ammonium excretion (typical for Renal Tubular Acidosis)."
