What is an ALT Blood Test?
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
What is it used for?
An ALT blood test is a type of liver function test. Liver function tests may be part of a regular checkup. The test can also help diagnose liver problems.
Why do I need an ALT blood test?
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:
Because ALT in the bloodstream can indicate liver damage before symptoms appear, your health care provider may order an ALT blood test if you are at a higher risk for liver damage. Risk factors for liver disease include:
- Family history of liver disease
- Heavy drinking
- Exposure or possible exposure to hepatitis virus
- Taking certain medicines that can cause liver damage
What happens during an ALT 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 ALT blood test. If your health care provider has ordered more tests on your blood sample, 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?
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.
Is there anything else I need to know about an ALT blood test?
ALT used to be called SGPT, which stands for serum glutamic-pyruvic transaminase. The ALT blood test was formerly known as the SGPT test.
- 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:
- 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.
- 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:
- 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:
- 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:
- 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
- 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:
- 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:
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The medical information provided is for informational purposes only, and is not to be used as a substitute for professional medical advice, diagnosis or treatment. Please contact your health care provider with questions you may have regarding medical conditions or the interpretation of test results.In the event of a medical emergency, call 911 immediately.