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Alanine Aminotransferase (ALT): About This Test

Location of the liver

What is it?

An alanine aminotransferase (ALT) test measures the amount of the enzyme ALT in the blood. ALT is found mainly in the liver. When ALT levels are higher than normal, it can mean that the liver is damaged or diseased.

Why is this test done?

The ALT test is done to:

  • Identify acute and chronic liver disease, such as cirrhosis and hepatitis, caused by alcohol, drugs, or viruses.
  • Help check for liver damage.
  • Find out whether jaundice was caused by a blood disorder or liver disease.
  • Keep track of the effects of cholesterol-lowering medicines and other medicines that can damage the liver.

How do you prepare for the test?

Avoid strenuous exercise just before having an ALT test.

How is the test done?

A health professional uses a needle to take a blood sample, usually from the arm.

How long does the test take?

The test will take a few minutes.

What happens after the test?

  • You will probably be able to go home right away.
  • You can go back to your usual activities right away.

Follow-up care is a key part of your treatment and safety. Be sure to make and go to all appointments, and call your doctor or nurse call line if you are having problems. It's also a good idea to keep a list of the medicines you take. Ask your doctor when you can expect to have your test results.

Where can you learn more?

Go to https://www.healthwise.net/patientEd

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