Urine Anion Gap Calculator

Calculate the urine anion gap to estimate urinary ammonium excretion.

Aug 31, 2026 Renal #acid-base #urine-anion-gap #renal-tubular-acidosis #ammonium

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All fields required unless noted

Urine sodium (mEq/L)

Urine potassium (mEq/L)

Urine chloride (mEq/L)

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Formula & Clinical Notes

Formula

Urine AG = (UNa + UK) − UCl

Clinical Notes

The urine anion gap = (UNa + UK) − UCl and indirectly estimates urinary ammonium. In non-anion gap metabolic acidosis, a negative urine anion gap suggests appropriate renal ammonium excretion (e.g., GI bicarbonate loss), while a positive gap suggests impaired ammonium excretion (e.g., renal tubular acidosis). It is most reliable when urine pH is below 6.5.

Sources

StatPearls — Anion Gap and Non-Anion Gap Metabolic Acidosis