What is an ALT Blood Test?

The alanine aminotransferase (ALT) test is a blood test that checks for liver damage.

Your liver does lots of important things for you:

• Makes a fluid called bile that helps your body digest food.
• Removes waste products and other toxins from your blood.
• Produces proteins and cholesterol.

Diseases like hepatitis and cirrhosis can damage your liver and stop it from doing its many roles.

Why Is ALT Important?

This enzyme is found mainly in your liver. Smaller amounts of ALT are in your kidneys and other organs, too.

Your body uses ALT to break down food into energy. Normally, ALT levels within the blood are low. If your liver is damaged, it will release more ALT into your blood and levels will rise. (ALT used to be called serum glutamic-pyruvic transaminase, or SGPT).

Doctors often give the ALT test together with other liver tests.

Symptoms of liver disease or damage, such as:

• Stomach pain or swelling
• Nausea
• Vomiting
• Yellow skin or eyes (a condition called jaundice)
• Weakness
• Extreme tiredness (fatigue)
• Dark-colored urine
• Light-colored poop
• Itchy skin

Why you should have this test?

• You've been exposed to the hepatitis virus.
• You drink a lot of alcohol.
• You have a family history of liver disease.
• You take medicine that's known to cause liver damage.

What Do the Results Mean?

You should get your results in about a day. A normal ALT Blood Test result can range from 7 to 55 units per liter (U/L). Levels are normally higher in men.

Slightly high ALT levels may be caused by:

• Alcohol abuse
• Cirrhosis (long-term damage and scarring of the liver)
• Mononucleosis
• Drugs such as statins, aspirin, and some sleep aids

Moderately high ALT levels may be because of:

• Chronic (ongoing) liver disease
• Alcohol abuse
• Cirrhosis
• Blockage of the bile ducts
• Heart attack or heart failure (when your heart can’t pump enough blood to your body)
• Kidney damage
• Muscle injury
• Damage to red blood cells
• Heat stroke
• Too much vitamin A

Very high ALT levels can be caused by:

• Acute viral hepatitis
• An overdose of drugs such as acetaminophen (Tylenol)
• Liver cancer
• Sepsis

5. ALT usually is done as part of a group of liver function tests called a liver panel.
5. This panel also includes an aspartate aminotransferase (AST) test. AST is another liver enzyme. As with ALT, the levels of AST in your blood rise if your liver is damaged.

Comparing ALT with AST levels gives your doctor more information about the health of your liver. The ALT-to-AST ratio can help your doctor figure out how severe the liver damage is and what might have caused it.