Jaundice in cats happens when a yellow pigment called bilirubin builds up in the blood and stains the skin, gums, ear flaps, and whites of the eyes. Visible yellowing typically appears once bilirubin levels exceed about 3 mg/dL. The causes fall into three broad categories: problems that destroy red blood cells too quickly, diseases that damage the liver itself, or blockages that prevent bile from draining normally.
How Bilirubin Builds Up
About 80% of bilirubin comes from the normal recycling of old red blood cells. When these cells break down, their oxygen-carrying protein releases a compound called heme, which the body converts first into a green pigment and then into orange-yellow bilirubin. This raw bilirubin travels to the liver bound to a protein in the blood, where liver cells process it and send it into bile. Bile flows through a duct system into the intestines, and that’s how bilirubin leaves the body.
Any disruption along this path, whether red blood cells are breaking down too fast, the liver can’t process bilirubin properly, or bile can’t drain, causes bilirubin to accumulate. Because bilirubin bonds strongly to elastic tissue in the skin and the whites of the eyes, jaundice can linger for days even after the underlying problem starts to resolve. A form of bilirubin that locks permanently onto blood proteins has a half-life of 10 to 14 days, which explains why some cats stay visibly yellow well into recovery.
Red Blood Cell Destruction (Pre-Hepatic Causes)
When red blood cells are destroyed faster than the liver can clear the resulting bilirubin, jaundice develops. This is sometimes the most dramatic form because it can come on quickly and cause severe anemia at the same time. A cat with this type of jaundice often has pale or yellow gums, rapid breathing, weakness, and lethargy.
Several infections target red blood cells directly. Mycoplasma species (formerly called Haemobartonella) are blood parasites spread by fleas that attach to red blood cells and trigger the immune system to destroy them. Cytauxzoon felis, carried by ticks, is a particularly dangerous parasite in cats across the southeastern United States that can cause rapidly fatal anemia. Babesia and Ehrlichia infections are less common in cats but can also cause hemolysis.
Certain toxins and household substances are equally dangerous. Acetaminophen (Tylenol) is extremely toxic to cats because they lack the liver enzyme needed to process it safely. Even a single standard tablet can cause massive red blood cell damage. Onions, garlic, and zinc (found in some coins and hardware) also destroy red blood cells. Immune-mediated hemolytic anemia, where the cat’s own immune system attacks its red blood cells without an obvious trigger, is another possibility.
Liver Disease (Hepatic Causes)
Fatty Liver Disease
Hepatic lipidosis, or fatty liver syndrome, is one of the most common liver diseases in cats and a frequent cause of jaundice. It happens when a cat stops eating and the body responds by flooding the liver with stored fat. The liver can’t process this sudden overload, so fat accumulates inside liver cells and shuts down normal function.
In more than 90% of cases, fatty liver disease is triggered by another underlying condition, such as obesity, diabetes, pancreatitis, kidney disease, hyperthyroidism, or cancer, that causes the cat to lose its appetite. The key warning sign is a cat that has stopped eating for more than two to three days, especially an overweight cat. Symptoms include dramatic weight loss (sometimes more than 25% of body weight), vomiting, lethargy, drooling, and an inability to hold the head up normally. Jaundice is a hallmark finding. With aggressive nutritional support, often through a feeding tube placed by a veterinarian, many cats recover. But without treatment, fatty liver disease is fatal.
Cholangiohepatitis
Cholangiohepatitis refers to inflammation of the bile ducts and surrounding liver tissue. Cats develop two distinct forms. The acute (neutrophilic) form is caused by bacterial infection, usually bacteria that travel up from the intestines through the bile duct into the liver. Cats with this form get sick suddenly, with fever, abdominal pain, vomiting, jaundice, and poor appetite. More than half of affected cats also have inflammation of the intestines or pancreas at the same time.
The chronic (lymphocytic) form is an immune-mediated disease where the body’s own immune cells infiltrate the bile ducts and liver without any bacterial infection present. It tends to progress more slowly. Inflammatory bowel disease is a significant risk factor, and Persian cats may have a genetic predisposition. Both forms cause jaundice because the inflamed, swollen bile ducts can’t move bilirubin out of the liver efficiently.
Other Liver-Related Causes
Feline infectious peritonitis (FIP) can target the liver. This viral disease causes widespread blood vessel inflammation, and infected immune cells can settle in the liver, kidneys, brain, and other organs, forming granulomas that disrupt normal tissue. Cats with FIP may develop jaundice alongside fluid buildup in the abdomen, fever, and weight loss. Toxoplasmosis, a parasitic infection, can also inflame the liver and cause jaundice along with fever, abdominal swelling, and neurological signs. Liver flukes, tumors, and certain medications round out the list of hepatic causes.
Bile Duct Blockage (Post-Hepatic Causes)
When the common bile duct is physically blocked, bile can’t reach the intestines. Bilirubin backs up into the bloodstream, and the cat turns yellow. A sudden, complete obstruction typically causes lethargy, fever, jaundice, vomiting, and notably pale or clay-colored stools (because bile pigments never reach the gut to give stool its normal color).
Pancreatitis is one of the most common culprits. The pancreas sits right next to the bile duct, and when it swells, it can compress or completely block bile flow. Gallstones (cholelithiasis) and gallbladder mucoceles, where the gallbladder fills with thick, gel-like mucus, can also obstruct the duct. Tumors in the pancreas, bile duct, or surrounding intestine are another cause, particularly in older cats. Less commonly, intestinal inflammation (duodenitis), parasitic infections, or scarring from previous inflammation can narrow or block the bile duct.
How Veterinarians Identify the Cause
Because the list of possible causes is long, vets follow a systematic approach. The starting workup typically includes a complete blood count, blood chemistry panel, urinalysis, and testing for feline leukemia and feline immunodeficiency virus. The first question to answer is whether red blood cells are being destroyed. A blood count reveals anemia, and a blood smear examined under the microscope can show infectious organisms clinging to red blood cells or signs that the immune system is attacking them. If the red blood cell count is normal, the cause is in the liver or bile ducts.
Abdominal ultrasound is considered essential for evaluating the liver and biliary system. It can reveal an enlarged or shrunken liver, fat accumulation, masses, swollen bile ducts, gallstones, or fluid in the abdomen. If a mass or abnormal tissue is found, ultrasound-guided fine needle aspiration lets the vet collect a small sample for further analysis without major surgery. Clotting times are checked first, since liver disease often impairs the blood’s ability to clot normally.
Signs to Watch For at Home
Jaundice in cats is easier to miss than in people because fur hides skin color. The earliest visible sign is usually a yellow tint inside the ears, on the gums, or in the whites of the eyes. You might also notice dark orange or brown urine, which reflects excess bilirubin being filtered through the kidneys.
The symptoms that typically accompany jaundice depend on the cause but commonly include loss of appetite lasting more than a day or two, vomiting, lethargy, weight loss, diarrhea, increased thirst and urination, and abdominal swelling. A cat that has stopped eating entirely for 48 hours or more deserves prompt veterinary attention, both because of the risk of fatty liver disease and because appetite loss is often the first clue to serious illness in cats.