Urine Anion Gap calculator
Result
-20mmol/L
Negative — adequate NH₄⁺ excretion (GI loss likely)
Normal = slightly negative to 0. UAG reflects unmeasured NH₄⁺ (inverse).
How to use it
- 1
Spot urine Na, K, Cl. Collect simultaneously; random sample acceptable.
- 2
UAG = UNa + UK − UCl. NH₄⁺ excretion ↑ in GI diarrhoea → UAG negative. Renal tubular acidosis → UAG positive.
- 3
Normal UAG ≈ 0 to slightly negative. In normal acid excretion, Cl slightly exceeds Na + K.
When to use it
- Normal anion gap metabolic acidosis
- Distinguish diarrhoea (negative UAG, appropriate NH₄⁺) from RTA (positive UAG, inadequate NH₄⁺).
- Type 1 vs Type 4 RTA
- Both positive UAG; urine pH distinguishes (< 5.5 = Type 4, > 5.5 = Type 1).
- Not valid if AKI or low urine Na < 25
- Dilutional effect invalidates result.
A reference for clinicians and students, not medical advice. A score supports a decision; it does not make one. Check every result against the patient in front of you and your local protocol.
At a glance
- Specialty
- Nephrology
- Inputs
- 3
- Type
- Formula
