Alanine aminotransferase (ALT) is a liver enzyme; an abundant quantity of ALT is present in the liver and kidney cells. A small amount of ALT is also present in the muscles and heart. In normal physiology, a low level of ALT in the blood is present. An elevated level of ALT in the blood is an indication of the problem. But why does the ALT level increase in dogs? What is the main reason behind the elevation?

Liver damage or injury is one of the biggest reasons that cause an increase in ALT level. However, an elevated amount of ALT is not always related to liver damage. Many non-liver diseases cause an increase in ALT levels. For example, heart failure and intestinal inflammation cause an increase in ALT levels up to 4-5 times. Severe dental anomalies can also cause an elevation in ALT level. Frequently ingestion of toxins and inflammation of the liver causes an increase in ALT levels in dogs.

ALT has a crucial role in maintaining the normal functioning of the body. Its increase can cause several problems in dogs. Read which problems are associated with ALT increase in dogs? And how can you diagnose and treat those problems?

What is the function of the ALT in a dogs?

Liver enzymes have various functions in the body, and ALT is one of the most crucial liver enzymes in dogs. ALT catalyzes the conversion of the amino acids, alanine and aspartate in pyruvate.

Pyruvate is a source of energy for the cells. Pyruvate fulfills the daily energy requirements of the cells and keeps them working. So, alternatively, you can say that ALT helps to provide energy to the cell. ALT also aids the liver to perform its task like detoxification, regulates the level of chemicals in the body, and removes the waste products from the body.

Why does ALT level increase in a dogs?

Before discussing the elevated level of ALT in dogs, it is necessary to know what is the normal amount of ALT in dogs: The normal level of ALT in dogs ranges from 6 to 70 IU/L or International Units per Liter. Now let’s discuss the various reasons that cause an increase in ALT level in dogs.


X-linked muscular dystrophy (CXMD) causes a constant increase in serum ALT level. CXMP is a spontaneously occurring, degenerative, and progressive condition in dogs. In CXMD, dogs feel difficulty in breathing and eating. In some cases, dogs develop severe and fatal respiratory ailments and mortality is very high in this situation.

In CXMD, almost 50% of dogs die before reaching 15 months of age. And 50% who survive develop a risk of congestive heart failure.

Hepatocellular Necrosis

Hepatocellular necrosis is also one of the prominent reasons for the increase in ALT level. Any liver injury causes a peak increase in ALT level in dogs. The peak value of the ALT could be seen after 1-2 days of the hepatic insult or injury. The half-life of the ALT enzyme is short. So, after 2-3 days, the level of ALT that has increased due to hepatic injury starts to decrease.

Muscle Damage

ALT also increases in response to muscle damage. So, an elevated level of ALT could be indicative of muscle injury. When there is a sudden increase in the ALT level of dogs, it is crucial to know either it is liver damage or muscle? The elevated level of creatine kinase helps in the differential diagnosis to evaluate if the ALT level is increased due to muscle or liver damage. When the ALT level has increased due to muscle damage, then the amount of creatine kinase increases severalfold more than normal.

Endogenous Causes

ALT level in dogs also increases due to extrahepatic diseases that secondarily affect the liver eg: canine hyperthyroidism. In dogs, the level of ALT moderately increases due to anticonvulsant therapy and biliary stasis.

Other than these, several other conditions cause an increase in the level of ALT in dogs. We will try to mention all the conditions that can increase the level of ALT.

Metabolic causes

The most common metabolic causes that cause an elevation in the ALT level in dogs are Diabetes mellitus, Hyperadrenocorticism, and hyperthyroidism.

Hypoxic causes

Hepatic congestion, Thrombosis, Anema, Seizures, and sepsis

Neoplastic causes

Lymphoma, Metastasis Neoplasia, Hepatocellular carcinoma

Inflammatory causes

Chronic, acute hepatitis, Cholangitis, Cholanglohepatitis, Cholecystitis,


Infection of several types causes an increase in the ALT level. Most common of them include Leptospirosis, Histoplasmosis, Feline infectious Peritonitis, Schistosomiasis, ascending bacterial infection.

Other causes of the increase include Stereos Hepatopathy, Benign nodular, and hemolysis.

Exogenous Causes

Along with the endogenous, several exogenous causes cause an increase in the level of ALT. The most famous of them include:


Medication is a crucial exogenous cause that can increase the level of ALT in dogs.

The medication that causes an increase in ALT level in dogs includes:

  • tetracycline
  • Carprofen
  • Phenobarbitone
  • Azathioprine
  • Antifungal medication
  • Trimethoprim-sulfadiazine
  • Lomustine.

These medications can cause a moderate to a marked increase in ALT level. So if you are using any of the above-mentioned medications, for your four-footed friend for a long time, then keep in mind that your dog can face an increase in ALT level.


The most common toxins that cause an increase in the ALT level are cycads, xylitol, zinc, aflatoxins, amanita, mushrooms, blue-green algae, carbon tetrachloride, and heavy metals.

External Trauma

Any external trauma to the liver or muscles is also an exogenous source that causes an increase in ALT level.

How to Interpret the Elevated ALT level of a dog?

It is essential to interpret the elevated level of ALT correctly. We have explained previously that the liver has excellent regenerative ability. So an early increase in the level of the ALT should not be used as a prognosis.

For example, a dog who has just suffered a traumatic injury might have a sky-high level of ALT. But this level of ALT will get lower after 2-3 days. A dog has an inborn capacity to tolerate the transient increase in ALT level. So, it is crucial to interpret the elevated ALT pattern with caution. Otherwise, it can cause complications.

Common Signs of Elevated ALT level in a dog

It is tough to observe the signs and symptoms of the elevated ALT level in the early stages. Dogs don’t show any sign of illness at the initial stages. The signs and symptoms became prevalent, usually in the acute stage, or when 75% or more liver damage has occurred.

Common early signs of the elevated ALT level could be:

  • Loss of appetite (the reason is still unknown)
  • Weakness and weight loss (because dogs stop taking proper diet)
  • Unstable gait (due to weakness)
  • Become dull
  • Often remain confuse and become less active towards environmental stimuli
  • Increase in the level of thirst and urination
  • Dark urine or tea-colored urine
  • Light-colored stool or clay-colored stool
  • Skin itchiness

Early signs of elevated ALT levels are so common that pet parents often associate them with several different factors.

The late signs of the condition are the sign of the diseases that are due to the elevated level of ALT. For example, you might observe the yellowing of the eye in the late stage, it is due to jaundice. Moreover, blood in poop, seizures, and ascites are occasional late signs.

How to check Elevated ALT level in dog?

Several tests could help you to check the level of ALT in your dog. These tests will help you to know the severity of the disease. And also to know the root cause of the problem.

Serum Biochemistry Test

The test gives an insight into all the chemicals present in the body. As the name suggests, in this test, the serum of the dogs is evaluated. It checks for the presence of several enzymes and chemicals. By comparing test result values with the normal, the veterinarian can tell the severity of the disease.

Liver Function Test

A liver function test could be used as a landmark to check the elevated level of liver enzymes. A liver function test checks the level of ALT in the body. In this test, the level of ALT Is measured simultaneously with AST (another liver enzyme).

The liver function test comprehensively shows the level of all liver enzymes. With the help of a liver function test, a veterinarian can evaluate the elevated level of ALT in dogs.

Tests for Protein and Electrolyte

Tests for protein and electrolytes could also help in ALT level diagnosis. A marked increase in the level of protein could be indicative of a high ALT value.

If the test result has shown a marked increase in the ALT value, then your veterinarian might suggest several tests for your four-footed friend to know the cause of the disease. In the case of a 5-7 fold increase in ALT value, a veterinarian might suggest the following test:

  • Test for hepatitis A, hepatitis B, and hepatitis C.
  • Test for the exposure of drug toxins and other poisonous material that might have caused a marked increase in the ALT value.
  • Examination and test for muscular dystrophy, and an overall examination to examine the muscle injury.

In case your veterinarian is suspecting a severe liver injury as the root cause. Then he may perform a liver biopsy. A liver biopsy helps to know the real cause of liver injury, and it also helps to know the extent of liver damage.

How to Treat Elevated ALT level in a dog?

The liver has an immense ability to fix a moderate increase in the ALT level. So, If there is only a 2-3 fold increase in the ALT level, then you don’t need to provide any specific treatment to your dog. In moderate cases, a dog’s liver can fix everything. But, in case there is a marked increase, you should go for the proper treatment of your dog.

The best treatment for elevated ALT levels is prevention. By prevention, we mean that we avoid the long-term use of the medicine that can cause an increase in ALT level.

Avoid the exposure of the toxins and other factors that could be the potential reason for ALT increase.

If the level of ALT has increased due to any disease, then try to treat that disease. For example, vaccination in case of hepatitis.

Supportive treatment is the best treatment for dogs, who are suffering an increase in ALT value due to any trauma. You should provide your dog with an ample amount of vitamins, and minerals, to speed up the healing process.

In the end, a diet change can help you to treat an elevated level of ALT. A certain diet might cause toxicity in a dog’s body and cause an increase in ALT level. Hence, consider a change in diet if your dog has a moderate increase in the ALT level.


ALT is one of the most important liver enzymes and helps the liver to carry out its function proficiently. Moreover, ALT also helps the body to carry out some important reactions of the body.

An increase in the level of the ALT is not uncommon in dogs. However, a marked increase (or 5-7 fold increase) could be dangerous for dogs. The signs and symptoms appear at a late stage. So if you are expecting any liver disease in your dog, you should go for a diagnostic test that can help you know the ALT level of your dog. As a result, you can choose the prevention and treatment for your dog accordingly.