What this calculator does
BUN-to-creatinine ratio works out compares blood urea nitrogen to creatinine, used to help distinguish causes of kidney injury. 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
The inputs explained
| Field | What to enter |
|---|---|
| Blood urea nitrogen (BUN) (mg/dL) | A number, measured in mg/dL. Starts at 14. |
| Creatinine (mg/dL) | A number, measured in mg/dL. Starts at 1. |
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 blood urea nitrogen (bun)
Every other input is held at the calculator’s starting values while blood urea nitrogen (bun) varies. Select any row to load that scenario into the calculator.
| Blood urea nitrogen (BUN) (mg/dL) | BUN-to-creatinine ratio | Typical reference range | Reading |
|---|---|---|---|
| 7 | 7.0:1 | 10:1 - 20:1 | Below the typical range |
| 10.5 | 10.5:1 | 10:1 - 20:1 | Within the typical range |
| 14 | 14.0:1 | 10:1 - 20:1 | Within the typical range |
| 21 | 21.0:1 | 10:1 - 20:1 | Above the typical range: can suggest reduced blood flow to the kidneys, dehydration or GI bleeding |
| 28 | 28.0:1 | 10:1 - 20:1 | Above the typical range: can suggest reduced blood flow to the kidneys, dehydration or GI bleeding |
| 42 | 42.0:1 | 10:1 - 20:1 | Above the typical range: can suggest reduced blood flow to the kidneys, dehydration or GI bleeding |