What this calculator does
Urine anion gap works out urinary electrolyte gap that helps distinguish causes of a normal anion-gap metabolic acidosis. Enter your own figures above and the answer updates as you type: nothing is fixed in the code, so the result reflects exactly the numbers you supply.
The formula this calculator evaluates is printed under the tool and explained below, so you can check the working by hand or reuse it in a spreadsheet.
The formula
FormulaUrine anion gap = (Urine Na + Urine K) − Urine Cl
The inputs explained
| Field | What to enter |
|---|---|
| Urine sodium (mEq/L) | A number, measured in mEq/L. Starts at 40. |
| Urine potassium (mEq/L) | A number, measured in mEq/L. Starts at 30. |
| Urine chloride (mEq/L) | A number, measured in mEq/L. Starts at 80. |
Worked examples
Every figure in the tables below is produced by this page’s own calculator at build time, so the numbers and the tool always agree. Select any row to load that scenario.
How the answer changes with urine sodium
Every other input is held at the calculator’s starting values while urine sodium varies. Select any row to load that scenario into the calculator.
How the answer changes with urine sodium
| Urine sodium (mEq/L) | Urine anion gap | Commonly cited reference range | Reading |
|---|---|---|---|
| 20 | -30.0 mEq/L | about 0 to 10 mEq/L in healthy adults | Negative: suggests high urinary ammonium excretion, more typical of a GI cause such as diarrhoea |
| 30 | -20.0 mEq/L | about 0 to 10 mEq/L in healthy adults | Negative: suggests high urinary ammonium excretion, more typical of a GI cause such as diarrhoea |
| 40 | -10.0 mEq/L | about 0 to 10 mEq/L in healthy adults | Negative: suggests high urinary ammonium excretion, more typical of a GI cause such as diarrhoea |
| 60 | 10.0 mEq/L | about 0 to 10 mEq/L in healthy adults | Positive: suggests low urinary ammonium excretion, more typical of a renal cause of acidosis |
| 80 | 30.0 mEq/L | about 0 to 10 mEq/L in healthy adults | Positive: suggests low urinary ammonium excretion, more typical of a renal cause of acidosis |
| 120 | 70.0 mEq/L | about 0 to 10 mEq/L in healthy adults | Positive: suggests low urinary ammonium excretion, more typical of a renal cause of acidosis |