Test Quick Guide

Alanine aminotransferase, usually referred to as ALT, is an enzyme concentrated primarily in the liver. Enzymes are proteins that facilitate important functions in the body.

An ALT test measures the amount of this enzyme in the blood. ALT levels can increase when liver cells are damaged, so the test can be used to evaluate the condition of the liver.

In general, ALT is not tested alone. Instead, it is usually measured along with other liver enzymes as part of a panel test like the liver panel or comprehensive metabolic panel (CMP).

About the Test

Purpose of the test

The purpose of an ALT test is to help assess the health of the liver. Damage to cells in the liver can cause ALT to leak into the blood, so a test can help detect liver problems.

ALT is commonly tested with other liver enzymes and compounds in the blood. Together, these measurements can be used for diagnosis, screening, and monitoring.

  • Diagnosis is testing that happens after symptoms have started. Its goal is to find the problem or cause for symptoms. ALT testing may be useful in the diagnosis of symptoms that can be tied to liver problems like nausea and vomiting, abdominal pain, itching, jaundice, fatigue, and appetite loss.
  • Screening tries to find health problems before any symptoms have occurred. With some liver conditions, ALT levels may rise in the blood before symptoms begin, so testing for ALT and other liver enzymes may be ordered for early detection. This is usually recommended if you have risk factors for liver disease, such as heavy alcohol use, diabetes, obesity, or a family history of liver problems. Even if you don’t have risk factors, order tests that measure ALT during routine health checkups.
  • Monitoring includes all the methods used to keep track of how your condition progresses. If you have had liver disease or an abnormal ALT test, ongoing testing may be used to see how your levels change over time. ALT and liver enzyme tests can also monitor for side effects of medications affecting liver health and function.

What does the test measure?

An ALT test measures the level of this enzyme, ALT, in your blood.

ALT is one of several enzymes that help the liver function properly. Although small amounts of ALT can be found in other parts of the body, it is predominantly found in the liver.

In most cases, ALT is not measured by itself. Instead, ALT is normally one of several measurements in a liver panel or CMP. Taking multiple measurements along with ALT provides more context for evaluating liver health.

When should I get an ALT test?

ALT testing is appropriate in a range of medical circumstances. It is often prescribed as an initial diagnostic test if you have symptoms that could be explained by an underlying problem affecting your liver.

Even if you have general symptoms, a panel test that includes ALT may be used in the diagnostic process. The liver panel or CMP, including ALT, may be part of a basic evaluation in urgent care or the emergency room.

As a tool for early detection of liver disease, ALT can be periodically measured with other liver enzymes even if you don’t have any symptoms. Your doctor may recommend screening involving ALT if you are at higher risk of liver disease.

ALT testing may also be included in your typical medical checkups. But data is limited to show that widespread screening offers more benefits than downsides, including added medical costs and unnecessary medical procedures.

Follow-up ALT testing can be used if you’ve had a previous test with an abnormal result. If you’ve been diagnosed with liver disease in the past, repeated ALT testing can help monitor the progression of the disease. When your doctor prescribes a medication that can affect your liver, ALT testing can be a tool to watch for unwanted side effects.

Finding an Alanine Aminotransferase Test

How can I get an alanine aminotransferase test?

Testing for ALT is normally done as part of a panel of measurements prescribed by a physician. The ALT test is performed on a blood sample typically taken from a vein in your arm in a hospital, laboratory, clinic, or doctor’s office.

Can I take the test at home?

There are options for at-home ALT tests, but it is much more common to have this test done in a medical setting.

Certain at-home test kits include several measurements related to liver health, including ALT. With these tests, you can collect a blood sample at home, but you must mail it to a laboratory where it can be analyzed. At-home tests do not usually require a prescription.

How much does the test cost?

How much an ALT test costs varies. Factors influencing the cost include whether other measurements are tested along with ALT, where the test is conducted, and whether you have health insurance.

In addition, it is important to know that the total cost associated with the test may be the sum of several different components, including:

  • Charges for the technician who draws your blood
  • Charges for the laboratory that measures ALT and any other compounds in your blood
  • Charges for the office visit when the test is prescribed
  • Charges for an office visit to review your test results

These different charges are often paid for by your health insurance company if the test is prescribed by your doctor. However, you may still have out-of-pocket costs like a deductible or copay. Contact the customer care department of your health insurance provider for details about specific expected costs for an ALT test.

Taking an Alanine Aminotransferase Test

An ALT test is conducted with a blood sample obtained using a needle inserted into a vein in your arm. This type of blood draw is a routine procedure normally done at a doctor’s office or a similar medical setting.

In an at-home version of the test, you collect a small blood sample using the provided test materials and then package your sample to be mailed to a laboratory.

Before the test

Because ALT is most commonly tested along with other measurements in a panel, you usually will be told to fast for up to 12 hours before your blood test. During this time, you cannot eat any food or drink anything besides water.

When ALT is tested alone, fasting is not necessary. For this reason, check with your doctor about the details of your scheduled test. Follow any instructions from your doctor about fasting beforehand.

Many different types of medications and supplements have the potential to affect your ALT levels. Before the test, tell your doctor about any drugs or dietary supplements that you are taking. In some cases, you may be told to stop taking certain medications before the test.

Because ALT is also present in muscle, intense exercise also can influence your ALT levels, so tell your doctor ahead of time if you frequently engage in demanding physical workouts.

If you are taking an at-home test, make sure to read the included instructions completely so that you know how to properly carry out each step of the test process.

During the test

A technician or nurse will take a blood sample for your ALT test. They will tie an elastic band around the top part of your arm, which increases blood flow in your veins. Then they will apply an antiseptic to a small section of your arm and insert a needle into a vein to withdraw a vial of blood.

The entire process takes only a few minutes. It is normal to feel a brief sting or throbbing pain when the needle is inserted or removed from your arm.

For at-home tests, blood is taken from your fingertip. The test kit usually includes an antiseptic, a small needle, and special test paper. After cleaning and pricking your fingertip, you can place a drop of blood on the test paper that is then mailed to a lab.

After the test

A blood draw is a common and routine procedure that usually has few side effects. Normally a bandage is applied to the puncture site to stop it from bleeding. Some people have bruises or pain in their arm after the test, but these effects are rarely long-lasting.

If you are told to fast before the blood draw, it’s often helpful to bring a snack so that you can eat something soon after the test is done. You can usually drive and resume most normal activities once your blood has been drawn.

After an at-home ALT test, you may need to put a bandage on your finger if it doesn’t stop bleeding on its own. Other side effects are rare. Once you have obtained your blood sample, you must properly package it and place it in the mail.

Alanine Aminotransferase Test Results

Receiving test results

Results for your ALT test are usually available within a few business days. You may be told of your test results by your doctor’s office. Usually, you can also obtain a copy of the test report by mail or electronically.

Results from at-home tests of ALT are typically accessed electronically through a smartphone app or a specific website. Getting the results may take a few extra days because of the time it takes for your sample to arrive by mail to the laboratory.

Interpreting test results

The test report should have a line that shows both your ALT level as well as the reference range that the laboratory uses to categorize ALT levels as normal or abnormal. In most cases, ALT will be measured in units per liter (U/L) or international units per liter (IU/L).

When reviewing your results, remember there is no universal reference range for ALT. There can be variation in laboratory methods that affect what is considered normal. For this reason, it’s important to look at the range provided by the specific lab that analyzed your blood.

Most often, ALT is tested along with other liver enzymes and proteins in a panel test. Your test report will show your levels and the lab’s reference range for each measurement. This is important because your test results are interpreted by looking at these test components together.

High levels of ALT can be a result of damage or injury to cells. Because ALT is most concentrated in the liver, abnormal ALT test results are generally associated with conditions affecting the liver, such as inflammation (hepatitis) and scarring (cirrhosis).

At the same time, ALT can be elevated without any underlying health problem. Multiple factors can affect ALT; in most cases, high ALT is not a sign of severe liver disease.

To interpret your test result, your doctor takes multiple factors into account. These include your current health and health history as well as the levels of other measurements on your test. In addition, your doctor may consider individual factors that can influence your normal level of ALT, including:

  • Exercise: Intense or extreme exercise can cause a temporary boost in ALT levels.
  • Medications: A number of medications and supplements can alter ALT measurements.
  • Sex: Males typically have higher levels of ALT, which is believed to be related to hormonal differences.
  • Menstruation: ALT levels can go up or down during the course of the menstrual cycle.
  • Age: There is a tendency for ALT levels to decrease with older age, although the exact reason for this is not known.
  • Body mass index: Several research studies have found an association between ALT levels and body mass index, which may change the interpretation of test results in people with obesity.

When ALT levels are very high, it may indicate an acute liver problem. Mild or moderate elevation, especially if it persists on several tests over time, can be an indicator of a chronic disease. However, the degree of elevation alone is not a reliable predictor of the extent of injury to the liver.

Because many types of liver problems can cause ALT levels to increase, the test alone cannot identify an underlying cause. Although uncommon, ALT can be elevated as a result of disease outside the liver. Looking at how ALT levels relate to other liver enzymes can provide clues that may help the doctor assess your situation and recommend any appropriate follow-up testing.

Your physician can best help you understand the diverse factors affecting your interpretation of your ALT test and what your results mean for your overall health.

A conversation with your doctor about your ALT test can help ensure that you are informed about your results. Some of the following questions may make it easier to cover key information when you talk with your physician:

  • What was my ALT level? Was it in the normal reference range?
  • Were any other measurements taken? If so, were they normal or abnormal?
  • What do the test results mean for my overall health?
  • Do you recommend any follow-up tests? If so, which ones, and what are their benefits and risks?


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