ALT Blood Test
Reviewed
Also called: Alanine aminotransferase, Serum Glutamic-Pyruvic Transaminase (SGPT), GPT, Alanine Transaminase
An ALT test measures the amount of ALT in your blood. This test is commonly used to help diagnose liver damage or disease.
Specimen: blood
Why this test may be ordered
- As part of a routine checkup to screen liver health.
- If you have symptoms of liver damage such as nausea, vomiting, lack of appetite, fatigue, weakness, jaundice, abdominal swelling or pain, ankle/leg swelling, dark urine, light-colored stool, or frequent itching.
- If you have a high risk of liver damage due to family history of liver disease, alcohol use disorder, obesity, diabetes, certain medicines that can cause liver damage, or hepatitis or exposure to hepatitis.
Preparation and collection
You may need to stop taking certain medicines before the test, so tell your provider about everything you take. But don't stop taking any medicines unless your provider tells you to.
A health care professional will take a blood sample from a vein in your arm, using a small needle. This usually takes less than five minutes.
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.
Understanding results
An ALT blood test is often done as part of a group of liver function tests. Liver function tests measure several different proteins, substances, and enzymes that show how well your liver is working.
What does high ALT mean?
Higher-than-usual levels of ALT in your blood: Higher-than-usual levels of ALT in your blood may be a sign of liver damage from: hepatitis, infection, cirrhosis, liver cancer, other liver diseases, a lack of blood flow to the liver, certain medicines, such as cholesterol or pain medicines, poisons. Limitation: If your results show you have a high level of ALT, it doesn't always mean that you have a medical condition that needs treatment. Many things can affect your results, such as your age, sex, weight, and certain medicines and dietary supplements. Next step: To learn what your results mean, talk with your provider.- Lower-than-usual levels of ALT in your blood: Lower-than-usual levels of ALT in your blood are not common. Your provider may do more tests since this may be a sign of: B6 deficiency, chronic kidney disease. Limitation: Your ALT levels can also be affected by intense exercise and where you are in your menstrual cycle. Next step: To learn what your results mean, talk with your provider.
- 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
Your provider usually compares your ALT results with the results of the other liver tests to evaluate your liver health and decide if you need other tests to make a diagnosis.
- What do my ALT results mean in combination with my other liver function tests?
- Do I need any additional tests based on my ALT level?
- Should I make any changes to my medicines or lifestyle based on my results?
Evidence source
Source: U.S. National Library of Medicine (MedlinePlus). Practices and reference ranges may differ in your country.