BUN/creatinine ratio blood test
Blood urea nitrogen to creatinine ratio
In short
A typical adult BUN/creatinine ratio result is 10 to 20 ratio. A high ratio most often points to low fluids or a high-protein diet rather than the kidneys. It means more when BUN is also high. Always read your result against the range printed on your own report.
BUN divided by creatinine, a clue to the cause of changes.
The lab divides your BUN by your creatinine. The ratio helps doctors tell kidney causes apart from others, such as low fluids or bleeding in the gut. It matters most when BUN or creatinine is out of range.
Is my BUN/creatinine ratio high or low?
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Typical range
| For | Range | Unit |
|---|---|---|
| Adults | 10–20 | ratio |
Typical ranges for adults. Labs differ a little, so the range printed next to your result is the one to go by.
If your BUN/creatinine ratio is high
A high ratio most often points to low fluids or a high-protein diet rather than the kidneys. It means more when BUN is also high.
Common reasons
- Not drinking enough, or losing fluid through vomiting or diarrhea
- A high-protein diet
- Low muscle mass, which lowers creatinine and lifts the ratio
- Steroid medicines
- Less often: reduced blood flow to the kidneys, as with heart failure
- Less often: bleeding in the stomach or upper gut
If your BUN/creatinine ratio is low
A low ratio is less common and often reflects a low-protein diet. It means more when BUN or creatinine is also out of range.
Common reasons
- Eating little protein
- Drinking a lot of fluid
- Pregnancy
- A muscular build, which raises creatinine
- Less often: severe liver disease or muscle breakdown
What can throw it off
Low muscle mass lowers creatinine, which can push the ratio up on its own.
Questions to take to your appointment
- 1Are my BUN and creatinine each in range?
- 2Could low fluids or my diet explain the ratio?
Read together with
Doctors rarely read BUN/creatinine ratio alone. These usually sit next to it.
Quick answers
What is the BUN/creatinine ratio blood test?
BUN/creatinine ratio (Blood urea nitrogen to creatinine ratio): BUN divided by creatinine, a clue to the cause of changes. The lab divides your BUN by your creatinine. The ratio helps doctors tell kidney causes apart from others, such as low fluids or bleeding in the gut. It matters most when BUN or creatinine is out of range.
What is a normal BUN/creatinine ratio level?
For most adults, BUN/creatinine ratio is typically 10 to 20 ratio. Labs differ a little, so the range printed next to your result is the one to go by.
What does a high BUN/creatinine ratio mean?
A high ratio most often points to low fluids or a high-protein diet rather than the kidneys. It means more when BUN is also high. Common reasons include not drinking enough, or losing fluid through vomiting or diarrhea; a high-protein diet; low muscle mass, which lowers creatinine and lifts the ratio; and steroid medicines. A doctor reads it together with your other results and how you feel.
What does a low BUN/creatinine ratio mean?
A low ratio is less common and often reflects a low-protein diet. It means more when BUN or creatinine is also out of range. Common reasons include eating little protein; drinking a lot of fluid; pregnancy; and a muscular build, which raises creatinine.
What can affect my BUN/creatinine ratio result?
Low muscle mass lowers creatinine, which can push the ratio up on its own.
What should I ask my doctor about my BUN/creatinine ratio?
Questions worth taking to the appointment: Are my BUN and creatinine each in range? Could low fluids or my diet explain the ratio?
What this page can’t do
It reads each number on its own.
Doctors read results together — ALT with AST, ferritin with hemoglobin, TSH with free T4. A pattern says more than any single flag.
It doesn't know you.
Your age, your medicines, how you feel and your last result all change what a number means.
It doesn't remember.
Close this page and your results are gone. That's on purpose: nothing was ever sent to us.
We also make Vita: Health Coach, an app for those parts. It reads your whole report with your medicines and history in mind, answers follow-up questions in plain words, and keeps your reports in one place — for you and for the people you look after.
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