ALT Blood Test
Reviewed
This test measures the amount of ALT (alanine transaminase) in your blood. ALT is an enzyme found mainly in the liver. When liver cells are damaged, they release ALT into the bloodstream. The test is commonly used to help diagnose liver damage or disease and is often part of a group of liver function tests.
Preparation and collection
You may need to stop taking certain medicines before the test; tell your provider about everything you take but do not stop any medicine unless your provider tells you to. An ALT test is usually ordered with other blood tests, and you may need to fast (not eat or drink) for several hours before those tests. Your provider will give you specific instructions.
Understanding this test
Use the reference interval and units printed by the laboratory that performed the test. A result outside that interval is not a diagnosis by itself, and a result inside it does not rule out every condition. Your symptoms, history, medicines, timing, and related tests can change what the result means.
- An ALT blood test alone is not diagnostic; your provider will compare your ALT results with other liver function tests and may need to perform additional tests to make a diagnosis.
- Many factors can affect your results, including age, sex, weight, certain medicines, dietary supplements, intense exercise, and menstrual cycle.
- The amount of ALT in your blood is not related to how much your liver may be damaged.
What to do next
Talk with your provider to understand what your results mean and whether any follow-up tests or actions are needed.