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AST Test

What is an AST Test?

AST (aspartate aminotransferase) is an enzyme that is found mostly in the liver, but also in muscles. When your liver is damaged, it releases AST into your bloodstream. An AST blood test measures the amount of AST in your blood. The test can help your health care provider diagnose liver damage or disease.

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

What is it used for?

An AST blood test is often included in a routine blood screening. The test may also be used to help diagnose or monitor liver problems.

Why do I need an AST blood test?

You may get an AST blood test as part of your routine checkup or if you have symptoms of liver damage. These may include:

  • Nausea and vomiting
  • Weight loss
  • Tiredness
  • Weakness
  • Jaundice, a condition that causes your skin and eyes to turn yellow
  • Swelling and/or pain in your abdomen
  • Swelling in your ankles and legs
  • Dark-colored urine and/or light-colored stool
  • Frequent itching

Even if you don't have symptoms, your health care provider may order an AST blood test if you are at a higher risk of liver disease. Risk factors for liver disease include:

  • A family history of liver disease
  • Heavy drinking
  • Obesity
  • Diabetes
  • Taking certain medicines that can cause liver damage

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 don't need any special preparations for an AST blood test. If your health care provider has ordered other blood tests, you may need to fast (not eat or drink) for several hours before the test. Your health care provider will let you know if there are any special instructions to follow.

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?

High levels of AST in the blood may indicate hepatitis, cirrhosis, mononucleosis, or other liver diseases. High AST levels can also indicate heart problems or pancreatitis. If your results are not in the normal range, it doesn't necessarily mean that you have a medical condition needing treatment. A variety of factors that can affect your results. These include your age, gender, diet, and types of medicines you take. To learn what your results mean, talk to your health care provider.

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 aminotransferase, 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. You may also have an AST test part of a series of liver function tests. In addition to AST and ALT, liver function tests measure other enzymes, proteins, and substances in the liver.

References

  1. American Liver Foundation. [Internet]. New York: American Liver Foundation; c2017. Liver Function Tests; [updated 2016 Jan 25; cited 2017 Mar 13]; [about 4 screens]. Available from: http://www.liverfoundation.org/abouttheliver/info/liverfunctiontests/
  2. Hinkle J, Cheever K. Brunner & Suddarth's Handbook of Laboratory and Diagnostic Tests. 2nd Ed, Kindle. Philadelphia: Wolters Kluwer Health, Lippincott Williams & Wilkins; c2014. Aspartate Aminotransferase; p. 68–69.
  3. Lab Tests Online [Internet]. Washington D.C.: American Association for Clinical Chemistry; c2001–2017. Aspartate Aminotransferase: The Test; [updated 2016 Oct 26; cited 2017 Mar 13]; [about 4 screens]. Available from: https://labtestsonline.org/understanding/analytes/ast/tab/test/
  4. Lab Tests Online [Internet]. Washington D.C.: American Association for Clinical Chemistry; c2001–2017. Aspartate Aminotransferase: The Test Sample; [updated 2016 Oct 26; cited 2017 Mar 13]; [about 3 screens]. Available from: https://labtestsonline.org/understanding/analytes/ast/tab/sample/
  5. National Heart, Lung, and Blood Institute [Internet]. Bethesda (MD): U.S. Department of Health and Human Services; What Are the Risks of Blood Tests?; [updated 2012 Jan 6; cited 2017 Mar 13]; [about 6 screens]. Available from: https://www.nhlbi.nih.gov/health/health-topics/topics/bdt/risks
  6. National Heart, Lung, and Blood Institute [Internet]. Bethesda (MD): U.S. Department of Health and Human Services; What Do Blood Tests Show?; [updated 2012 Jan 6; cited 2017 Mar 13]; [about 6 screens]. Available from: http://www.nhlbi.nih.gov/health/health-topics/topics/bdt/show
  7. National Heart, Lung, and Blood Institute [Internet]. Bethesda (MD): U.S. Department of Health and Human Services; What To Expect with Blood Tests; [updated 2012 Jan 6; cited 2017 Mar 13]; [about 5 screens]. Available from: https://www.nhlbi.nih.gov/health/health-topics/topics/bdt/with
  8. University of Rochester Medical Center [Internet]. Rochester (NY): University of Rochester Medical Center; c2017. Health Encyclopedia: Aspartate Transaminase; [cited 2017 Mar 13]; [about 2 screens]. Available from: https://www.urmc.rochester.edu/encyclopedia/content.aspx?contenttypeid=167&contentid=aspartate_transaminase

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