ALT, which stands for alanine transaminase, is an enzyme found mostly in the liver. When liver cells are damaged, they release ALT into the bloodstream. An ALT test measures the amount of ALT in the blood. High levels of ALT in the blood can indicate a liver problem, even before you have signs of liver disease, such as jaundice, a condition that causes your skin and eyes to turn yellow. An ALT blood test may be helpful in early detection of liver disease.

Other names: Alanine Transaminase (ALT), SGPT, Serum Glutamic-Pyruvic Transaminase, GPT

Your health care provider may have ordered liver function tests, including an ALT blood test, as part of a routine exam or if you have symptoms of liver damage. These may include:

• Nausea and vomiting
• Jaundice
• Abdominal pain
• Loss of appetite
• Unusual itching
• Tiredness

An ALT blood test is often part of liver function testing. Liver function tests measure several different proteins, substances, and enzymes and can determine how well your liver is working. Your health care provider may compare your ALT results with the results of other liver tests to help learn more about your liver function. High levels of ALT may indicate liver damage from hepatitis, infection, cirrhosis, liver cancer, or other liver diseases.

Other factors, including medicines, can affect your results. Be sure to tell your health care provider about all the prescription and over-the counter medicines you are taking.

1. American Liver Foundation. [Internet]. New York: American Liver Foundation; c2017. Liver Function Tests; [updated 2016 Jan 25; cited 2017 Mar 18]; [about 3 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. Alanine Aminotransferase (ALT); p. 31.
3. Lab Tests Online [Internet]. Washington D.C.: American Association for Clinical Chemistry; c2001–2017. ALT: The Test; [updated 2016 Apr 28; cited 2017 Mar 18]; [about 4 screens]. Available from: https://labtestsonline.org/understanding/analytes/alt/tab/test/
4. Lab Tests Online [Internet]. Washington D.C.: American Association for Clinical Chemistry; c2001–2017. Liver Panel: The Test; [updated 2016 Mar 10; cited 2017 Mar 18]; [about 4 screens]. Available from: https://labtestsonline.org/understanding/analytes/liver-panel/tab/test/
5. Mayo Clinic [Internet]. Mayo Foundation for Medical Education and Research; c1998–2017. Diseases and Conditions: Liver disease; 2014 Jul 15 [cited 2017 Mar 18]; [about 3 screens]. Available from: http://www.mayoclinic.org/diseases-conditions/liver-problems/basics/risk-factors/con-20025300
6. 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 18]; [about 6 screens]. Available from: Available from: https://www.nhlbi.nih.gov/health/health-topics/topics/bdt/risks
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 18]; [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: ALT; [cited 2017 Mar 18]; [about 2 screens]. Available from: https://www.urmc.rochester.edu/encyclopedia/content.aspx?contenttypeid=167&contentid=alt_sgpt