Urine Anion Gap Calculator (UAG)

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Spot urine sodium concentration in mEq/L (equivalent to mmol/L). For scale, adults typically excrete 40-220 mEq of sodium over 24 hours, but the UAG uses the concentration in this single sample, not the daily total. The UAG is unreliable when urine sodium is below 25 mEq/L.
mEq/L
Spot urine potassium concentration in mEq/L. For scale, adults typically excrete 25-125 mEq of potassium over 24 hours, but the UAG uses the concentration in this single sample, not the daily total.
mEq/L
Spot urine chloride concentration in mEq/L. For scale, adults typically excrete 110-250 mEq of chloride over 24 hours. A high chloride relative to Na + K drives a negative UAG.
mEq/L
Urine Anion GapNormal range
10mEq/L

Na+ + K+ - Cl-

InterpretationNormal range
Estimated Urinary NH4+Normal range
10 mEq/L
Extrarenal (high NH4+)<-10Normal-10-20Renal (low NH4+)20+

UAG is 10.0 mEq/L - Normal range

  • UAG = 50 + 30 - 70 = 10.0 mEq/L.
  • A UAG between -10 and +20 mEq/L is within the reference range for healthy adults. In the setting of metabolic acidosis, a value near zero may still be clinically significant.
  • In the absence of metabolic acidosis, a normal UAG is expected. In the setting of non-anion-gap acidosis, this value should be interpreted alongside serum electrolytes and urine pH.
  • The UAG is most reliable for evaluating non-anion-gap metabolic acidosis. It is less useful when urine sodium is below 25 mEq/L, or in the presence of ketoacidosis or other unmeasured urinary anions.

Next stepAlways interpret the UAG alongside clinical findings, serum bicarbonate, urine pH, and electrolytes. Consult nephrology for complex acid-base disorders.

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