normal bun in dogs is 9-27 mg/dL , bun is the level of urea nitrogen in the blood... it can be accociated with both the liver and kidneys and can indicate a number of things depending on if its too high or too low... with out knowing wether it is high or low i cant tell you what it could indicate,.
also i am not a vet just a vet tech a vet should be able to explain it better.
if there are abnormalities it can be something to be concerned about and the cause should be isolated
American or Canadian laboratory? The metrics are different...why was it done? Was your pet ill or was it for a wellness test? How old is your pet? Cat or Dog? BUN stands for Blood Urea Nitrogen and elevations can indicate something as simple as a little thirst or dehydration but can also indicate serious urinary tract or kidney disorders. Get back to me with a little more info and I can help a lot.