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Alanine Aminotransferase (ALT) Test
An alanine aminotransferase (ALT) test measures the amount of this enzyme in the blood. ALT is found mainly in the liver, but also in smaller amounts in the kidneys, heart, muscles, and pancreas. ALT was formerly called serum glutamic pyruvic transaminase (SGPT).
ALT is measured to see if the liver is damaged or diseased. Low levels of ALT are normally found in the blood. But when the liver is damaged or diseased, it releases ALT into the bloodstream, which makes ALT levels go up. Most increases in ALT levels are caused by liver damage.
The ALT test is often done along with other tests that check for liver damage, including aspartate aminotransferase (AST), alkaline phosphatase, lactate dehydrogenase (LDH), and bilirubin. Both ALT and AST levels are reliable tests for liver damage.
Why It Is Done
The ALT test is done to:
- Identify 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 medicines that can damage the liver.
How To Prepare
Avoid strenuous exercise just before having an ALT test.
How It Is Done
A health professional uses a needle to take a blood sample, usually from the arm.
How long the test takes
The test will take a few minutes.
How It Feels
When a blood sample is taken, you may feel nothing at all from the needle. Or you might feel a quick sting or pinch.
There is very little chance of having a problem from this test. When a blood sample is taken, a small bruise may form at the site.
Each lab has a different range for what's normal. Your lab report should show the range that your lab uses for each test. The normal range is just a guide. Your doctor will also look at your results based on your age, health, and other factors. A value that isn't in the normal range may still be normal for you.
Results are usually available within 12 hours.
High levels of ALT may be caused by:
- Liver damage from conditions such as hepatitis or cirrhosis.
- Lead poisoning.
- Very strenuous exercise or severe injury to a muscle.
- Exposure to carbon tetrachloride.
- Decay of a large tumor (necrosis).
- Many medicines, such as statins, antibiotics, chemotherapy, aspirin, opioids, and barbiturates.
- Growth spurts, especially in young children. Rapid growth can cause mildly elevated levels of ALT.
Current as of: June 17, 2021
Author: Healthwise Staff
E. Gregory Thompson MD - Internal Medicine
Adam Husney MD - Family Medicine
Martin J. Gabica MD - Family Medicine
Kathleen Romito MD - Family Medicine
Jerome B. Simon MD, FRCPC, FACP - Gastroenterology
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