Urine Anion Gap Calculator
Urine Anion Gap (UAG) = [Na+] + [K+] – [Cl-]
Meaning of UAG: Is ammonia genesis functioning properly?
UAG negative: ammonia is well produced → acid is being excreted (normal).
UAG positive: ammonia is poorly produced → acid is not excreted (abnormal).
* When Urine Anion Gap is unreliable *
(In such cases, calculating the Urine Osmolar Gap may be helpful.) [see below]
When polyuria is present / Urine pH > 6.5 / Urine Na < 20 mmol/L
When urinary ammonium is excreted with anions other than Cl-
(e.g., keto acids, acetylsalicylic acid, D-lactic acid, large amounts of penicillin)
Urine Osmolal Gap Calculator
Calculated Urine Osm =
(2 x Urine Na) + (2 x Urine K) + (glucose [mg/dL] / 18) + (BUN [mg/dL] / 2.8)
Urinary Osmolal gap = Measured Urine Osm – Calculated Urine Osm
*If Measured Urine Osm is not entered, only Calculated Urine Osm will be computed.
In non-diabetic patients, Urine Glucose may be excluded from the calculation.
Urine Osmolal Gap usually reflects the ammonium level.
If Urine Osmolal Gap ≤ 40 mmol/L with normal AG gap acidosis,
it indicates impaired Urine ammonium excretion.
(Exception: presence of large amounts of non-dissociated acids,
such as beta-hydroxybutyric acid in DKA.)
