FrançaisWhat bilirubin measures on your dog’s blood work
About 80% of bilirubin is made from the hemoglobin of old or damaged red blood cells, broken down by scavenger cells of the spleen, liver and bone marrow. The rest comes from other iron-containing proteins [1].
This first form is called unconjugated or indirect bilirubin. It does not dissolve in water, so it travels in the blood attached to albumin. The liver takes it up and attaches a sugar to it: it becomes conjugated or direct bilirubin, which dissolves in water and leaves with the bile into the gut. Normally, only very small amounts of conjugated bilirubin are found in blood [1].
Most reports give total bilirubin (TBIL), the sum of both forms. Some laboratories also give the “split” into direct and indirect bilirubin. It can help, but the results do not always fit neatly, because several processes often happen at the same time in a sick dog [1].
How to read the total bilirubin line on the report
Each result line has five parts. Read them together before looking at the flag.
- Abbreviation TBIL, T-BIL or TBILI all mean total bilirubin. A separate DBIL line, when present, is the direct (conjugated) part.
- Result The amount measured in this sample. It says how much pigment is in the blood, not where the problem started.
- Unit mg/dL here. Many laboratories outside the US use µmol/L: multiply mg/dL by 17.1 to convert [1].
- Laboratory interval The range of healthy dogs for this laboratory. For comparison, the Merck Veterinary Manual lists 0–0.3 mg/dL (0–5.1 µmol/L) [9]. Always use the interval printed on your report.
- Flag H means above the interval. It shows where the value sits, not why.
Yellow gums or eyes (jaundice, also called icterus) usually become visible once total bilirubin is above about 3 mg/dL [1]. Below that, the value can be high on the report while the dog does not look yellow.
A few things can skew the number. With some analyzers, a hemolyzed or fatty (lipemic) sample can read falsely high. Bilirubin is broken down by light, so a sample left in the light for several days can read falsely low [1]. In dogs, a meal did not change total bilirubin for up to 8 hours in one study cited by eClinPath [1].
Why bilirubin can be high: before, in or after the liver
Vets often sort a high bilirubin into three groups, based on where the problem sits along the path of the pigment [1]. In a study of 115 dogs with high bilirubin seen at two referral hospitals in Australia, 15.7% had a cause before the liver, 44.3% a cause in the liver and 36.5% a cause after the liver [5].
| Group | What happens | Examples in dogs |
|---|---|---|
| Before the liver (pre-hepatic) | Red blood cells break down faster than the liver can clear the pigment. A healthy liver copes with a lot, so bilirubin rises mostly when destruction is severe and rapid. The value is then often below 3–5 mg/dL and mostly unconjugated [1]. | Immune-mediated hemolytic anemia (IMHA), blood parasites such as Babesia, reactions to a transfusion [5]. In dogs with IMHA, bile flow can also slow down, so the conjugated form can rise too [1]. |
| In the liver (hepatic) | Liver cells take up, process or release bilirubin less well. Both forms can rise [1]. | Infectious hepatitis, toxic injury, liver tumors, chronic hepatitis [5]. Severe body-wide inflammation (sepsis) can also block the release of bile from liver cells [1]. |
| After the liver (post-hepatic) | Bile cannot flow out through the gallbladder and bile duct. Conjugated bilirubin backs up into the blood and spills into the urine [1]. | Gallbladder mucocele, gallstones, tumors, and a bile duct squeezed by pancreatitis [3, 5]. A full blockage or a burst bile system can push bilirubin to 20–30 mg/dL [1]. |
A gallbladder mucocele is a gallbladder filled with abnormal, thick mucus. It is seen mainly in older, small purebred dogs, often alongside hormonal diseases such as an underactive thyroid or Cushing’s disease, and it is diagnosed by ultrasound [7]. Thick bile like this can slow bile flow [3].
Pancreatitis is a common cause of a blocked bile duct in dogs. In 46 dogs with this problem, bilirubin first rose a median of 7 days after the signs began, and 31 of the 33 dogs that survived were managed without surgery [6].
Bilirubin in the urine: a little can be normal in dogs
Only conjugated bilirubin passes into urine, and the urine dipstick detects only this form. When bile flow slows, bilirubin often shows up in the urine before it rises in the blood [1, 4].
Dogs are an exception among pets. Their kidneys let small amounts of bilirubin through, so a trace to 1+ reaction can be normal in concentrated dog urine, particularly in males. The same reaction is potentially too much in more dilute urine, with a specific gravity below 1.030, and a 3+ reaction is not expected in a dog whatever the concentration [1]. In cats and most other species, bilirubin in the urine points to a problem with bile flow [1, 4].
That is why your vet reads the bilirubin pad together with the urine specific gravity, as explained in our guide to the urinalysis. Old samples or samples left in the light can give a falsely negative result [4].
GGT in dogs: an enzyme of the bile ducts
GGT (gamma-glutamyl transferase) sits on the surface of cells that line hollow organs. The GGT found in blood comes mainly from the cells lining the bile ducts in the liver. It rises when bile flow is physically slowed, when these cells multiply in response, or when they are damaged [2]. The GGT of the kidney, pancreas and gut is shed into urine or into the gut, so diseases of these organs do not raise blood GGT [2].
GGT is usually read with ALP, the other enzyme that rises when bile flow is slowed. In a study of 270 dogs with liver biopsies, ALP was normal in 15% of dogs with liver disease, but GGT was normal in 54%. GGT was, however, more specific: it stayed normal in 87% of dogs without liver disease, against 51% for ALP [10]. In other words, GGT misses more cases than ALP, but a high GGT is less often a false alarm. More about ALP in our article on high ALP in dogs.
| Situation | What GGT does | Source |
|---|---|---|
| Bile flow slowed or blocked | Rises, sometimes to high levels when the blockage is outside the liver [3]. | Biliary disease, pancreatitis, mucocele [3]. |
| Steroid medicines, Cushing’s disease | Corticosteroids can raise GGT in dogs [2]. In 15 dogs with Cushing’s disease, 67% had a high GGT and 87% a high ALP [2]. | See Cushing’s disease in dogs. |
| Phenobarbital | Can increase GGT, usually mildly [2]. | Anti-seizure medicine. |
| Nursing puppies | Very high in the first days of life: about 100 times the adult value in 1- to 3-day-old pups [11], falling over about 10 days [2]. It comes from colostrum and rose within 24 hours of suckling, not in pups fed milk replacer [11]. This is expected, not a sign of liver disease [2]. | Normal finding. |
| Chronic hepatitis | Increased in about 61% of dogs, less often than ALT or ALP (about 85%) [8]. | A common long-term liver disease. |
| Sample problems | An underfilled heparin tube can raise GGT by 10–50%. Marked hemolysis or very high bilirubin can lower it [2]. | Ask whether a repeat is useful. |
What the pattern tells your vet, and what may come next
Your vet reads bilirubin and GGT with the other liver values and the blood count. A few patterns are useful:
- High bilirubin with anemia. A falling red cell count with signs of red cell destruction suggests a cause before the liver. Your vet looks for this on the complete blood count and blood smear [1, 5].
- High bilirubin with high ALP and GGT, higher than ALT. This pattern points toward slowed bile flow [3]. An abdominal ultrasound is then often used to look at the gallbladder and bile duct [6, 7].
- High bilirubin with normal ALP and GGT. These enzymes need time to rise, so they can still be normal when jaundice appears quickly [1].
- High GGT and ALP with a normal bilirubin. Mild or localized slowing of bile flow can raise the enzymes without changing bilirubin [3].
A bile acids test is generally not useful once bilirubin is high from a liver or bile problem: bile acids are then expected to be high too [3, 8]. Clotting tests may be added, because poor bile flow reduces the absorption of vitamin K [3].
The level of bilirubin also carries information. In the Australian study, dogs with a bilirubin above 60 µmol/L (about 3.5 mg/dL) at diagnosis had a higher risk of death, with a median survival of 9 days versus 65 days below that cut-off [5]. In dogs with chronic hepatitis, a high bilirubin is one of the findings most linked to a poorer outlook [8]. These are averages from hospital studies: the cause matters most, and many causes can be treated.
Related articles
Bilirubin and GGT are two lines among the liver values. These articles explain the others.
For an overview of all liver values, see high liver enzymes in dogs.
En français : bilirubine et GGT du chien.
Questions to ask your veterinarian
- Is my dog’s high bilirubin more likely to start in the blood, the liver or the bile ducts?
- Does the blood count show signs of red blood cells being destroyed?
- How do the ALP, GGT and ALT results fit with the bilirubin value?
- Was there bilirubin in the urine, and what was the urine specific gravity?
- Is an abdominal ultrasound useful now, and when should we repeat the blood work?
Get your dog’s whole report explained, value by value.
Bilirubin and GGT are two lines among many. AI DiagAnimals reads the full report, with its own intervals and units, and prepares the questions to bring to your vet. The service opens soon: leave your email to be told first.
Frequently asked questions
When should I worry about high bilirubin in my dog?
Call your vet promptly if your dog looks yellow, is weak, vomits or will not eat, whatever the number. In a study of 115 dogs seen at referral hospitals, a bilirubin above 60 µmol/L (about 3.5 mg/dL) at diagnosis was linked to a higher risk of death, and causes before the liver, mostly IMHA, carried the highest risk [5].
What are the normal liver function test values for dogs?
They depend on the laboratory and the analyzer, so always use the interval printed on the report. For comparison, the Merck Veterinary Manual lists total bilirubin at 0–0.3 mg/dL in dogs [9]. See also high liver enzymes in dogs.
What does a high GGT mean in a dog?
Most often that bile flow is slowed, or that the dog is receiving steroids or has Cushing’s disease. In nursing puppies a very high GGT is normal and comes from colostrum [2, 11].
Is bilirubin in my dog’s urine always a problem?
No. A trace to 1+ reaction can be normal in concentrated dog urine, especially in males. More than that, or any bilirubin in dilute urine, needs to be looked at [1].
Sources
- eClinPath, Cornell University College of Veterinary Medicine. Bilirubin. eclinpath.com/chemistry/liver/cholestasis/bilirubin
- eClinPath, Cornell University College of Veterinary Medicine. GGT (gamma-glutamyl transferase). eclinpath.com/chemistry/liver/cholestasis/gamma-glutamyl-transferase
- eClinPath, Cornell University College of Veterinary Medicine. Cholestasis. eclinpath.com/chemistry/liver/cholestasis
- eClinPath, Cornell University College of Veterinary Medicine. Urinalysis: chemical constituents. eclinpath.com/urinalysis/chemical-constituents
- Brough A et al. Clinical findings and assessment of factors associated with survival in dogs presenting with hyperbilirubinaemia: 115 cases in Victoria, Australia (2015–2020). Vet Rec Open. 2022;9(1):e42. doi.org/10.1002/vro2.42
- Wilkinson AR et al. Bile duct obstruction associated with pancreatitis in 46 dogs. J Vet Intern Med. 2020;34(5):1794-1800. doi.org/10.1111/jvim.15879
- Gookin JL et al. Diagnosis and management of gallbladder mucocele formation in dogs. J Am Vet Med Assoc. 2025;263(6):777-785. doi.org/10.2460/javma.24.12.0789
- Webster CRL et al. ACVIM consensus statement on the diagnosis and treatment of chronic hepatitis in dogs. J Vet Intern Med. 2019;33(3):1173-1200. doi.org/10.1111/jvim.15467
- Merck Veterinary Manual. Serum biochemical analysis reference ranges. merckvetmanual.com/reference-values-and-conversion-tables/reference-guides/serum-biochemical-analysis-reference-ranges
- Center SA et al. Diagnostic efficacy of serum alkaline phosphatase and gamma-glutamyltransferase in dogs with histologically confirmed hepatobiliary disease: 270 cases (1980–1990). J Am Vet Med Assoc. 1992;201(8):1258-1264. pubmed.ncbi.nlm.nih.gov/1358870
- Center SA et al. Effect of colostrum ingestion on gamma-glutamyltransferase and alkaline phosphatase activities in neonatal pups. Am J Vet Res. 1991;52(3):499-504. pubmed.ncbi.nlm.nih.gov/1674651
Laboratory methods and reference intervals vary. This article explains; it does not diagnose. For a decision about your pet, use the original report and talk to your veterinarian. Our editorial policy.