What is an AST test?

An AST blood test measures the amount of AST in your blood. This test is commonly used to help diagnose liver damage or disease.

AST (aspartate aminotransferase) is an enzyme, a protein that speeds up certain chemical reactions in your body. It is found mainly in your liver but also in your heart, muscles, and other tissues. Usually, you will have low levels of AST in your blood. When your liver or other cells that contain AST are damaged, they release AST into your blood. This can lead to high AST levels in your blood.

An AST test may be ordered by itself but is often ordered as part of a group of liver function tests.

Other names: SGOT test, serum glutamic oxaloacetic transaminase test; aspartate transaminase test

What is it used for?

An AST blood test is often part of a routine blood screening to check the health of your liver. The test may help diagnose or monitor liver problems. It may also help diagnose other health conditions.

Why do I need an AST blood test?

You may get an AST blood test as part of your routine checkup or to monitor the treatment of a liver problem. You may also need a test if you have symptoms of liver damage, which may include:

• Nausea and vomiting
• Lack of appetite
• Fatigue
• Weakness
• Jaundice, a condition that causes your skin and eyes to turn yellow
• Swelling and/or pain in your abdomen (belly)
• Swelling in your ankles and legs
• Dark-colored urine (pee) and/or light-colored stool (poop)
• Frequent itching

Even if you don't have symptoms, your health care provider may order an AST blood test if you're more likely to develop liver disease because of:

• A family history of liver disease
• Alcohol use disorder (AUD)
• Obesity
• Diabetes
• Taking certain medicines that can cause liver damage
• Hepatitis or exposure to hepatitis

What happens during an AST blood test?

A health care professional will take a blood sample from a vein in your arm, using a small needle. After the needle is inserted, a small amount of blood will be collected into a test tube or vial. You may feel a little sting when the needle goes in or out. This usually takes less than five minutes.

Will I need to do anything to prepare for the test?

You may need to stop taking certain medicines before the test, so tell your provider about everything you take. But don't stop taking any medicines unless your provider tells you to.

An AST test is usually ordered with other blood tests. You usually need to fast (not eat or drink) for up to 12 hours before these tests. Your provider will let you know if there are any special instructions.

Are there any risks to the test?

There is very little risk to having a blood test. You may have slight pain or bruising at the spot where the needle was put in, but most symptoms go away quickly.

What do the results mean?

Low levels of AST in the blood are usually considered normal.

High levels of AST in the blood may be due to liver disease or other liver problems. Other reasons you may have high levels of AST can include:

• Hepatitis
• Cirrhosis
• Mononucleosis
• Heart procedures or problems
• Pancreatitis
• Hemochromatosis (too much iron in the body)
• Deep burns
• Seizures
• Use of drugs that are toxic to the liver, especially alcohol use
• Surgery

If your results are not in the normal range, it doesn't always mean that you have a medical condition that needs treatment. Many things can affect your results, such as pregnancy, exercise, certain medicines, and your age or sex. Talk with your provider to learn what your results mean.

Learn more about laboratory tests, reference ranges, and understanding results.

Is there anything else I need to know about an AST blood test?

Your health care provider may order an ALT blood test along with your AST blood test. ALT stands for alanine transaminase, which is another type of liver enzyme. If you have high levels of AST and/or ALT, it may mean that you have some type of liver damage.