Why Is My Dog Or Cat’s BUN:Creatinine Ratio High Or Low?

Ron Hines DVM PhD

Normal blood and urine values

How tests are grouped

Causes of abnormal tests  

SDMA Kidney Test

Update On Kidney Disease

Your Dog And Cat’s BUN to Creatinine Ratio = BUN:Cr Ratio

Mathematically calculating the ration between the amount of urea and the amount of creatinine in your dog or cat ’s blood gives your veterinarian clues as to why your pets blood urea nitrogen level (BUN) might be high. Both BUN and Creatinine are metabolic wastes that your dog or cat needs to clear from its blood via its kidneys. I mention many of the causes of high BUN levels here  and creatinine here. Many of these causes can be ruled out or ruled in when BUN is considered in a ratio with the pets creatinine level. The two values should go up or down in tandem when kidney or urinary tract problems are the cause and so the ratio value should remain similar . When one is out of balance with the other, health problems outside the kidney might be your cat or dog’s underlying health problem.

Why Might My Pet’s BUN:Creatinine Ratio Be High?

A high BUN/Creatinine ratio value sometimes just means that your dog or cat was dehydrated when the blood sample was obtained. But since the test is not precise, the ratios cannot be relied upon entirely to rule out other causes.

Why Might My Pet’s BUN:Creatinine Ratio Be Low?

A low BUN/creatinine ratio is more likely due to refusal to eat, starvation, malnutrition, advanced liver disease or even late pregnancy.


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