Updated September 25, 2026. Fact-checked against veterinary sources; review by a licensed veterinarian is in progress. See our editorial policy.
Quick answer: Bilirubin is a yellow pigment made when old red blood cells are broken down, and it’s normally processed by the liver. In dogs, small amounts in concentrated urine can be normal, especially in males, because dog kidneys can process some bilirubin. In cats, any bilirubin in the urine is abnormal and should be investigated. Higher amounts can point to liver disease, blocked bile flow, or destruction of red blood cells.
Normal vs. abnormal
- Dogs: a trace or small amount in highly concentrated urine is often normal. Larger amounts, or bilirubin in dilute urine, are more significant.
- Cats: bilirubin shouldn’t be present at all. Even a small amount warrants further testing.
Possible causes of increased bilirubin
- Liver disease: hepatitis, fatty liver disease in cats, toxins, or cancer
- Blocked bile flow: gallbladder disease, bile duct obstruction, or pancreatitis
- Red blood cell destruction (hemolysis): immune-mediated anemia, some infections, or toxins such as onion or zinc
- Fever and serious infection, which can affect bile processing
- Not eating for a long time, in some cases
Signs that may go with it
- Yellow gums, skin, or whites of the eyes (jaundice)
- Dark yellow to orange urine
- Poor appetite, vomiting, weight loss
- Lethargy or weakness
- Pale gums (with anemia)
See your vet promptly if your pet has any of these, and urgently for jaundice, pale gums, or weakness.
Typical next steps
- Repeat urinalysis and check urine concentration
- Blood count to check for anemia
- Chemistry panel, including blood bilirubin and liver enzymes
- Bile acid test for liver function
- Abdominal ultrasound to look at the liver, gallbladder, and pancreas
- Infectious disease or toxin testing, depending on history
Treatment
Treatment depends entirely on the cause: for example, nutritional support and a feeding tube for feline fatty liver, surgery for bile duct blockage, immune-suppressing medication for immune-mediated anemia, or treatment for infection or toxin exposure.
What to avoid
- Liver “detox” supplements without a diagnosis, and never products with alpha-lipoic acid for cats.
- Acetaminophen, which damages the liver and red blood cells.
- Onions and garlic in any form, which damage red blood cells.
- Waiting if a cat has stopped eating, which risks fatty liver disease.
Frequently asked questions
Is bilirubin in my dog’s urine serious?
A small amount in concentrated urine is often normal. Your vet will consider the amount, urine concentration, and bloodwork.
My cat’s urine test showed bilirubin but she seems fine. What now?
It’s still worth further testing, since early liver or blood problems may not cause obvious signs.
Can diet change urine bilirubin?
Not directly. It reflects liver function and red blood cell breakdown.
Sources
- Merck Veterinary Manual: Urinalysis
- Cornell University College of Veterinary Medicine eClinPath: Urine bilirubin
- Merck Veterinary Manual: Hepatic disease in small animals
- Merck Veterinary Manual: Immune-mediated hemolytic anemia
This article is for general education and is not a substitute for care from your own veterinarian. Learn about The Pet Vet and our editorial policy.