Renal Tubular Acidosis Typing (1, 2, 4)
Assigns the type of a normal-anion-gap metabolic acidosis of renal origin, in order.
Open the calculator → Runs in your browser. Data leaves only if you deliberately send a problem report from the interactive tool.
Example
- Serum potassium
- Low
- Urine pH in acidosis
- 6.2
Result: Renal tubular acidosis type 1 - a urine pH of 6.2 during acidosis, above 5.5, points to type 1: the kidney cannot acidify the urine.
The tool opens with these values already filled in. Replace them with your own.
What the result means
- Type 4
- A high serum potassium. Checked first, so it decides even when the urine is alkaline.
- Type 1
- Potassium not high and a urine pH above 5.5 during acidosis: the kidney cannot acidify the urine.
- Type 2
- Potassium not high and a urine pH of 5.5 or less: the kidney can acidify once enough bicarbonate has been lost. FE bicarbonate above 15% supports it.
- Urine anion gap
- Reported but NOT used to type. Sources disagree on its direction in type 4; they agree it separates a renal cause from gastrointestinal bicarbonate loss.
- Not offered
- Type 3, a rare combined form rather than a step in this sequence.
What you enter
- Serum potassium
- Urine pH in acidosis
- FE bicarbonate (supporting)
- Urine anion gap (supporting)
How this is calculated
Renal tubular acidosis. StatPearls. NCBI Bookshelf NBK519044; and Merck Manual Professional Edition, Renal Tubular Acidosis. Typing sequence per both. Read the source ↗
A reference and educational tool. Not medical, legal, or financial advice, and not a substitute for clinician judgment.