BUN/Creatinine Ratio
The ratio of urea nitrogen to creatinine, used to help explain abnormal kidney values.
| Typical reference range | 6–22 ratio |
Ranges vary by laboratory, method, age and sex: always use the range printed on your own report. Why labs differ.
What it measures
This is BUN divided by creatinine. Because urea and creatinine are handled differently by the kidneys, their ratio helps distinguish causes of abnormal values.
Why it matters
A high ratio suggests causes outside the kidney such as dehydration, reduced blood flow or bleeding, while a normal ratio with both values high suggests intrinsic kidney disease. Some labs only report it when BUN or creatinine is abnormal.
What a high result can mean
High ratios are seen with dehydration, high protein intake, gastrointestinal bleeding, heart failure, corticosteroid use and catabolic states, or low creatinine from low muscle mass.
What a low result can mean
Low ratios can occur with low protein intake, liver disease, overhydration, pregnancy or high muscle mass/creatine use raising creatinine.
What affects the result
Strongly influenced by protein intake, hydration and muscle mass. Interpret only alongside the individual BUN and creatinine values.
Unit
Usually reported in ratio.
Also called on lab reports
Urea Nitrogen/Creatinine Ratio, BUN/Creat Ratio, BUN/Creatinine, BUN/Creat
Related tests: Kidney Function
This page is educational and does not replace advice from a healthcare professional.