What Is The Normal Liver Enzyme Level In A Dog?

A dog's liver has many responsibilities: breaking down toxins before they enter the body, removing waste products from the blood, storing energy, and giving blood the ability to clot. While the liver is enormously resilient — it can continue to function even after large portions have been removed — the levels of enzymes present in this critical organ can serve as a gauge of your dog's overall health. Blood tests can quantify enzyme levels to help a veterinarian evaluate liver function.

A typical blood test run by a veterinarian to evaluate liver function returns values on liver enzymes, proteins, and other compounds. Of these values, those of five particular enzymes are most significant in reaching a diagnosis. If the tests indicate abnormalities, including unusual elevations, it can signal liver disease or failure.

The five enzymes are:

• ‌Alanine aminotransferase (ALT)‌: Predominantly found in hepatocytes

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epithelial liver cells that form the organ's structure

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elevated ALT levels are usually a clear sign of liver damage, though this can also signal pancreatitis.

• ‌Aspartate aminotransferase (AST)‌: Another enzyme found in epithelial liver cells, elevated AST can signal damage to the liver or other parts of the body, such as the pancreas or muscles.
• ‌Alkaline phosphatase (ALP)‌: Found in the liver and bones, a high level of ALP may indicate liver damage or a bone disorder, while low levels could mean malnutrition or lymphoma.
• ‌Serum bilirubin‌: A yellowish pigment made when the liver breaks down red blood cells, excess serum bilirubin can cause jaundice and may signal autoimmunity, toxicity, infection, a blocked bile duct, or hepatic disease.
• ‌Gamma glutamyltransferase (GGT)‌: Found in the cells lining the liver bile ducts, GGT levels may be high as a result of cholestasis, or diminished bile flow.

There are multiple different enzymes and lab values that veterinarians use to assess the function and damage to a liver. The most common liver enzymes are the following:
ALT: Normal range is 12–118 IU/L
AST: Normal range is 15–66 IU/L
ALP: Normal lab ranges are 5–131 IU/L
GGT: Normal range is 1–12 IU/L

Other lab work values veterinarians use that are not enzymes to assess liver function/damage are the following:

ALB: 2.7–4.4 g/dL
Total Bilirubin: 0.1–0.3 mg/dL
Cholesterol: 92–324 mg/dL

The normal enzyme levels are listed below. Each value range is given in international units per liter (IU/L) or milligrams per deciliter (mg/dL).

A variety of symptoms are associated with liver disease. They can include:

• Vomiting
• Diarrhea
• Fever
• Weight loss
• Anorexia
• Gastric ulceration
• Impaired brain function
• Abnormal clotting
• Jaundice
• Buildup of fluid in the abdomen
• Producing abnormally large amounts of urine
• Excessive thirst
• Abnormally enlarged or abnormally small liver

Signs of impaired brain function because of liver disease can include:

• Weakness
• Blindness
• Excessive salivating
• Aggression
• Dementia
• Coma
• Seizures
• Pressing their head against surfaces
• Wandering aimlessly
• Staggering when walking

This and other severe symptoms usually occur in the later stages of liver disease, making early diagnosis even more critical, especially since enzyme levels may normalize at the end of the disease.

Especially as your dog ages, it's important to know their normal liver enzyme levels. Many veterinarians have comprehensive "senior panels" that they can run on your pet, which will include liver enzymes. The value in this bloodwork is in being able to compare the liver enzyme levels in a healthy pet to those of one developing liver disease. If your dog is consistently on the lower end of the scale, it might be significant to find elevated liver enzymes. Early diagnosis and treatment, regardless of your dog's age, is critical.

If your dog develops liver disease, your veterinarian will likely want to work with you on finding an underlying cause. While liver disease can develop on its own, it's worth discovering the root of the dysfunction rather than simply treating the symptoms. In addition to blood tests and a physical exam, your DVM may administer further diagnostics, such as a liver biopsy. Balancing electrolytes and acids and bases is a common treatment, as is nutrition appropriate for your dog's symptoms. When no other cause can be found, treatment focuses on slowing the disease and keeping complications under control.

Liver disease is common, especially in older dogs. Periodic laboratory tests, including liver function tests, are important to keep tabs on your dog's liver health. Knowing your healthy dog's enzyme levels can help you and your DVM identify changes quickly. Early diagnosis and treatment of liver disease is essential.