Urine Anion Gap Calculator
Calculate the urine anion gap from urine sodium, potassium, and chloride.
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Urine anion gap
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Indirect arithmetic estimate; not a direct urine ammonium measurement
Na — + K — − Cl —
About
The urine anion gap (UAG) is the difference between measured urine sodium plus potassium and urine chloride. It has been used as an indirect, qualitative estimate related to urinary ammonium excretion in selected acid–base evaluations. It is not a direct urine ammonium measurement and does not establish the cause of an acid–base disorder.
Formula
Interpretation
Units: Enter all three electrolytes in the same system. For these monovalent ions, mmol/L and mEq/L are numerically equivalent.
Worked example: Urine sodium 25, potassium 20, and chloride 60 mEq/L gives UAG = 25 + 20 − 60 = −15 mEq/L.
Limitations: Urine pH, diet, volume status, low urine sodium, unmeasured urinary anions, and the timing of the sample can affect interpretation. Direct urine ammonium, when available, is a different measurement.
FAQ
Disclaimer
Educational and informational reference only. Not intended to replace professional medical advice, diagnosis, treatment, or independent verification.