Why Is My Dog Or Cat’s Blood Ammonia Level High?

Ron Hines DVM PhD

To see what normal blood and urine values are for your pet, go here

For an explanation of causes of most abnormal blood and urine tests go here 

To see how tests are often grouped, go here

The Ammonia Level In Your Pet’s Blood

Determining blood ammonia levels in dogs and cats is not a common frontline blood test. But if your dog or cat is showing marked personality changes, it is one your veterinarian might suggest.

Perhaps your pet has begun to loose some of its prior training. Perhaps it is becoming more forgetful, confused or has lost some of its hygienic habits. If it is an elderly pet, cognitive dysfunction  (pet dementia) might be on you or your vet’s mind. Perhaps it is a younger pet that is experiencing similar problems or a sudden personality change.

Many possible causes need to be ruled out; and higher than normal blood ammonia levels related to liver disease is one of them.

The test is quite difficult to run with accuracy because ammonia levels are quite unstable in blood samples. So many veterinarians prefer the ammonia tolerance test (However, the ammonia tolerance test in itself has been known to cause severe neurological reactions).

Health Problems That Can Cause Too Much Ammonia (hyperammonemia) To Be Present In Your Pet’s Blood:

Those issues include : Hepatic Encephalopathy, other liver problems, circulatory defects aka Portosystemic Shunts, failing kidneys, inherited metabolic disorders in the processing of protein amino acids. and

possibly – excessively high protein diets in specific genetically susceptible pets.

Delay in processing your pet’s blood sample after it was collected, collection issues (hemolysis) can also result in falsely elevated blood ammonia reading.

Cats that have developed an arginine deficiency through malnutrition or not eating can also have elevated blood ammonia levels. (ref)

Health Problems That Can Cause Too Little Ammonia To Be Present In Your Pet’s Blood:

I know of none.

Complementary tests:

Tests for liver disease, (elevated Bile acids level is more accurate than liver enzyme levels for diagnosing portosystemic shunts),  liver ultrasound, liver biopsy, trial low protein diet and repeat test at a respected national veterinary laboratory if initial tests were performed “in house” are other things to consider.


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