Overview

An alanine aminotransferase test, also called an ALT test, is a blood test to check the health of your liver. ALT is a substance found mostly in the liver. If your liver is OK, the ALT level usually stays low. But when liver cells are irritated or damaged, ALT can leak into the bloodstream. So the ALT level can go up.

An ALT test usually isn't done by itself. It's often included in a group of tests called a liver panel or liver function tests. These blood tests also check for other substances related to liver health. Examples of these substances are albumin, bilirubin and aspartate transferase, also called AST.

Other names for an ALT test are:

  • Alanine transaminase test.
  • Serum glutamic-pyruvic transaminase test, also known as a SGPT test.

Why it's done

An ALT test helps look for liver disease or damage. The test may be done as part of routine blood work to check your general health.

Checking your ALT level can help find liver disease or damage early, even before you feel sick.

You may need an ALT test if you:

  • Have symptoms of liver disease such as belly pain, yellowing of the skin or eyes, or unexplained tiredness.
  • Take medicines or supplements that could affect the liver.
  • Have health conditions such as obesity, type 2 diabetes or high cholesterol, which increase the risk of some types of liver disease.
  • May have been exposed to a hepatitis virus.

An ALT test can help diagnose:

  • Alcoholic liver disease.
  • Inflammation of the liver.
  • Scarring of the liver, called cirrhosis.
  • Hepatitis A, B or C.
  • Infectious mononucleosis, also called mono.
  • Metabolic dysfunction-associated steatotic liver disease (MASLD), formerly called nonalcoholic fatty liver disease (NAFLD).
  • Metabolic dysfunction-associated steatohepatitis (MASH), formerly called nonalcoholic steatohepatitis (NASH).

An ALT test is not used to diagnose liver cancer. But it may be included with other tests as part of a complete workup if your healthcare professional thinks cancer is a possibility.

Risks

There's little risk in getting an ALT test. As with any blood test, possible risks may include:

  • Soreness or tenderness in the area where the blood is taken.
  • Bruising near the area where the blood is taken.
  • Bleeding.
  • Fainting or feeling lightheaded.
  • Infection of the area where the blood is taken. This is rare.

How you prepare

Most people don't need to do anything special to get ready for an ALT blood test. But here are a few helpful things to keep in mind.

  • Medicines. Some medicines and supplements may affect your ALT liver level. Tell your healthcare team about all the medicines and supplements you take. Include those bought without a prescription.
  • Food and drinks. A fatty meal may cause ALT to go up. Also, beverages high in sugar may cause a higher ALT level. So you may be told not to eat or drink for a while before the test, especially if you're also having other blood work done. Ask your healthcare team if you need to stop eating or drinking for a short while before the test.
  • Caffeine. There's no strong evidence that caffeine affects ALT test results. But tell your healthcare professional if you regularly have caffeine in large amounts.
  • Alcohol. Do not drink alcohol for at least 24 hours before your test. Even drinking a little bit of alcohol may raise your ALT level.
  • Exercise. Your healthcare professional may tell you not to exercise before your test. Recent exercise may cause a slight rise in the ALT level.

What you can expect

Before

You take an ALT test at a medical office, clinic, hospital or lab. If you're anxious about needles or have fainted during a blood test, tell your healthcare team. Also tell the team if you have a bleeding disorder.

During

A small sample of blood is needed to do an ALT blood test. The healthcare professional uses a small needle to take blood from a vein, usually in your arm. It takes just a few minutes.

After

You might have a small bruise or feel sore where the needle went in. That usually goes away in a day or two. You likely can return to your daily activities right away.

Results

Your healthcare team gives you the test results. Most people get ALT results in about 1 to 2 days. Test results help your healthcare team plan treatment, if needed.

When looking at your ALT results, keep these things in mind:

  • Slight changes in ALT are common and not always a concern.
  • One single ALT number doesn't tell the whole story. Your healthcare team looks at the ALT level over time.
  • ALT liver levels can go up and down based on exercise, diet or stress.

Results of an ALT blood test are given in units per liter (U/L). A healthy ALT range hasn't been established for infants. For people age 1 and older, a healthy range is as follows:

  • For males: 7 to 55 U/L.
  • For females: 7 to 45 U/L.

Note: Lab ranges may differ depending on the lab doing the test. Ask your healthcare professional what the target ALT goal is for you.

Low ALT result

A low ALT level usually isn't a concern. But sometimes it's caused by:

  • Too little vitamin B-6 in the body.
  • Lack of proper nutrition, called malnutrition.
  • Long-term kidney disease, also called chronic kidney disease.

High ALT result

A slight increase in the ALT level may be due to recent vigorous exercise, a fatty meal or some medicines.

A high ALT level may be caused by liver cell damage due to:

  • Alcohol-related liver disease.
  • Metabolic dysfunction-associated steatotic liver disease, also called MASLD. But some people with this condition do not have high ALT.
  • Metabolic dysfunction-associated steatohepatitis, also called MASH.
  • Hepatitis.
  • Inflammation or damage from medicines, toxins or supplements.
  • Liver cancer.
  • Scarring of the level, called cirrhosis.

Sometimes, an increase in ALT is not related to the liver. That's because some ALT is found in heart and muscle tissue. Other causes of high ALT are:

  • A type of extreme muscle tissue damage called rhabdomyolysis.
  • Congestive heart failure.
  • Heart attack.

If your ALT level is high, your healthcare team may:

  • Repeat the test in a few weeks or months.
  • Order other blood tests or imaging tests.
  • Talk with you about the medicines you take and how much alcohol you drink.
  • Send you to a liver specialist, if needed.

If you have questions about your test results or next steps, talk with your healthcare professional.

By Mayo Clinic Staff