What Does BUN Mean in Dogs and Cats?
Quick answer
BUN measures urea, a waste product from protein digestion that the kidneys remove. It rises with reduced kidney function, dehydration, a high-protein meal, or bleeding in the gut, and can fall with liver problems or low-protein diets. Vets read BUN together with creatinine and SDMA rather than on its own.
What is BUN?
Blood urea nitrogen reflects urea, made by the liver from protein breakdown and cleared by the kidneys.
Reference range
[Range pending sourced table] Reference ranges vary by lab and species. Use the range printed on your pet's report.
What can raise BUN
- Reduced kidney function
- Dehydration
- Recent high-protein meal
- Gut bleeding
What can lower BUN
- Liver dysfunction
- Low-protein diet
- Increased urination
Dogs vs cats
In dogs
A meal before testing can raise BUN in dogs.
In cats
Cats eat high-protein diets, which vets factor into BUN.
Why one value rarely tells the whole story
BUN reflects diet, hydration, and liver as well as kidneys. Hydration, recent meals, stress during the visit, medications, and how the sample was handled can all shift a result. Vets look at the whole panel, your pet's symptoms, and the trend across tests over time.
Conventional interpretation
Vets read BUN alongside creatinine and urine tests.
Whole-pet context
Note meal timing before the test, water intake, and stool color.
Supportive options are not a cure. Check with your veterinarian before adding any supplement.
Questions to ask your vet
- Was my pet fasted?
- How do creatinine and SDMA compare?
- Could dehydration explain this?
- How does this compare with my pet's previous results?
Frequently asked questions
Should my pet fast before bloodwork?
- Many vets prefer fasting to reduce meal effects. Follow your vet's instructions.
Can low BUN be a problem?
- Sometimes it points to reduced liver function, so vets check other liver markers.
What is a normal BUN range?
- Reference ranges vary by laboratory, analyzer, and species. Use the range printed on your pet's report and ask your vet how your pet's result compares.
Should BUN be rechecked?
- Your veterinarian decides based on how far from range the value is, your pet's symptoms, and other results. Trends over time are often more useful than one result.
Related lab values
Related guides
Educational support only. Not a diagnosis or substitute for veterinary care.
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