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Urine Anion Gap (UAG) = (Urine Sodium + Urine Potassium) - Urine Chloride, the standard published formula used as an indirect estimate of urinary ammonium excretion in the evaluation of normal anion gap metabolic acidosis. Commonly cited reference framing: a positive UAG is often discussed as suggestive of a renal cause (impaired ammonium excretion), while a negative UAG is often discussed as suggestive of a GI cause (such as diarrhea) — reference only, not an interpretation of any specific patient. Pure arithmetic on given lab values. For general reference and educational purposes only — not a medical diagnosis. Consult a doctor for actual acid-base assessment.
How it works
Enter urine sodium, urine potassium, and urine chloride. The tool applies the standard urine anion gap formula.
- Enter urine sodium (mEq/L).
- Enter urine potassium (mEq/L).
- Enter urine chloride (mEq/L).
- Click Calculate to see your results.
Examples
Urine Na 40, Urine K 30, Urine Cl 50
UAG = (40 + 30) - 50 = 20 mEq/L (positive) — commonly discussed as suggestive of a renal cause.
Who should use it
- Reviewing a normal-anion-gap acidosis work-up alongside a doctor.
- Nephrology education about acid-base disorder classification.
Industry applications
- Nephrology reference
- Internal medicine education
Advantages
- Simple, standard, widely taught formula.
- Uses three routinely available urine lab values.
Limitations
- An indirect estimate of ammonium excretion, not a direct measurement.
- Less useful outside the specific context of normal-anion-gap acidosis evaluation.
Common mistakes to avoid
- Applying UAG interpretation framing to a patient with a high-anion-gap (rather than normal-anion-gap) acidosis, where UAG is not the relevant tool.
- Mixing up which values are sodium, potassium, and chloride.
Best practices
- Use UAG specifically in the context of evaluating a normal-anion-gap metabolic acidosis, per commonly cited nephrology teaching.
Tips
- UAG is typically interpreted alongside serum anion gap and the overall acid-base picture, not as a standalone number.