What To Know About the ALT Blood Test Before Getting One

Mark Gurarie
·8 min read
1

Medically reviewed by Steffini Stalos, DO

The alanine transaminase (ALT) blood test measures the levels of ALT, an enzyme that your liver produces. Your primary care provider may recommend an ALT blood test to screen for and detect signs of liver conditions, such as hepatitis or fatty liver disease. Your provider may also work with a gastroenterologist (a doctor who specializes in the digestive system) or a hepatologist (a doctor who specializes in the liver) to assess the overall health of your liver.

During the test, a healthcare provider such as a phlebotomy technician (or, a specialist in blood tests) collects a sample of your blood and sends the sample into a lab for testing and evaluation. High levels of ALT in your blood can indicate a problem with your liver.

Purpose

ALT blood tests are a type of test that measures your liver function. If you have liver damage or live with liver disease, your liver releases ALT into your blood. Too much ALT in your blood supply can mean that you have an underlying liver condition.

Your healthcare provider can order an ALT blood test as part of a routine check-up or to screen for liver disease if you have diabetes, drink alcohol, or have a family history of liver problems. They may also recommend this test if you're displaying any signs of liver damage, such as:

An abnormal ALT blood test result doesn't automatically mean that you have a liver problem. This is because certain medications, such as Tylenol (acetaminophen), statin drugs, and birth control pills can also cause ALT levels to spike. However, your test results can help your provider order additional testing to check for the following liver conditions:

  • Viral hepatitis (e.g., hepatitis A, B, C, D, and E)

  • Alcoholic hepatitis

  • Autoimmune hepatitis

  • Liver cancer

  • Cirrhosis of the liver

  • Non-alcoholic fatty liver disease

  • Mononucleosis

How Does It Work?

If your healthcare provider determines that you need an ALT blood test, they will often order additional blood tests to test your overall liver function. They may also ask you to visit the testing services department at a hospital or make an additional appointment to come back for a blood test. They will also explain how the testing procedure works and when you can expect results.

Before the Test

Prior to ordering the ALT blood test, your healthcare provider will perform a physical exam. They will also ask you about your personal and family medical history, the symptoms you're experiencing, the medications you're taking, and your lifestyle habits.

If your provider suspects that you may have a liver condition or may be at risk for liver disease, they'll order an ALT blood test. Generally, you don't have to do much to prepare for your blood test. However, your provider may ask you to fast (or, refrain from eating or drinking) for at least eight hours before the test.

During the Test

The ALT blood test procedure involves collecting a sample of your blood from a vein in your arm, using a small and sanitized needle. Here’s what you can expect during the procedure:

  • Step 1: The phlebotomy technician locates a vein in your arm

  • Step 2: The technician cleans the skin around the vein

  • Step 3: The technician puts the needle in your vein and collects blood in a vial or test tube

  • Step 4: Once the test tube is done filling up, the technician removes the needle and cleans your skin with an alcohol

  • Step 5: The technician places a bandage on your arm to prevent or stop bleeding from the needle poke

After the Test

The ALT blood test is an outpatient procedure, meaning you won’t need to stay overnight. Generally, there isn't too much of a waiting period before and after taking the test. Once the test is over, you are free to go home.

Sometimes, it can take several days to get your test results. Once your healthcare provider receives your test results, they may upload your test results on a medical app that your clinic uses, call you about your test results, or ask you to set up a secondary appointment to discuss your results. Depending on your test results, you may have to undergo additional testing (such as more blood tests or an imaging test) or not need anything further.

Risks and Precautions

Like most blood tests, there are a few risks associated with the ALT blood test. The side effects of an ALT blood test are few and often manageable. After your blood test, there is some chance of experiencing bruising, tenderness, or pain in your arm where the blood was taken from. Generally, this pain passes within a few hours to a couple of days.

Additionally, this blood test is safe for all people. Specifically, there is no risk of taking the test for young children, pregnant people, those with underlying health conditions, or people older than 65.

However, it is important to let your healthcare provider know if you experience any unusual or worsening symptoms before or after taking the test. For example, jaundice or intense pain in your abdomen may warrant medical attention.

How to Prepare for the ALT Blood Test

ALT blood tests are standard procedures that technicians perform at medical clinics, hospitals, and doctor's offices. That said, you don't need to do much to prepare. However, your healthcare provider may ask you to be mindful of the following as you prepare for your appointment:

  • Wear a short-sleeved shirt or layers that you can take off so a technician can easily access your arm

  • Refrain from eating or drinking for at least eight hours prior to the appointment

  • Temporarily stop taking any medications (if necessary)

  • Reduce strenuous activity or exercise, as this can temporarily cause ALT levels to spike

  • Bring a health insurance card, an identification card, and a list of any medications you may be taking with you

  • Talk to your insurance company or hospital's billing department about whether the test is covered under insurance or what out-of-pocket costs may be

Results

Once you complete the blood test, your technician will prepare to send your blood sample to a lab for testing and evaluation. Oftentimes, it can take at least a few days for you to receive your results. You’ll likely get your results via an online patient portal, phone call, or during a second appointment. Your healthcare provider will explain your test results and talk to you about any necessary next steps.

Interpreting Your Results

It's important to note that the ALT blood test alone doesn't usually establish a diagnosis for liver conditions. Oftentimes, your healthcare provider will order several blood tests and compare your ALT levels with other test results.

What’s considered a healthy range for ALT varies from person to person. However, the normal range is generally between 7 to 56 international units of ALT per liter of blood (IU/L). Mildly elevated ALT levels are usually two to three times higher than the normal range. Severely elevated ALT levels can be up to 50 times greater than the normal range.

Elevated levels of ALT may imply liver damage or diseases of the liver, such as liver cancer, cirrhosis, and hepatitis. The test can also help healthcare providers understand whether your acute (or, temporary) issue or a chronic (or, long-term) problem is causing your ALT levels to spike. Depending on your results, your healthcare provider may also refer you to a gastroenterologist or hepatologist for further examination, such as imaging tests or biopsies.

If you have elevated ALT levels, your healthcare provider will compare your results to other blood and liver function tests. In some cases, your provider may recommend additional testing to confirm the results of your first test. Your healthcare provider may also order more tests if your ALT enzyme levels are within the normal range, but you have symptoms of liver damage.

In some cases, people have abnormally low ALT levels in the blood. This has been associated with malnutrition, frailty, aging, and loss of muscle mass (known as sarcopenia). That said, ALT blood tests showing low levels don’t confirm or rule out any health conditions—but are a good starting point to understanding more about your liver health and overall functioning.

A Quick Review

The ALT blood test is part of a panel of blood tests that measure your liver health and functioning. The purpose of the ALT blood test is to detect levels of the enzyme, alanine transaminase (ALT), in the blood. Elevated levels of this enzyme may indicate liver problems, such as cancer, infection, hepatitis, or cirrhosis (liver scarring). This test is often part of a routine check-up and can help your healthcare provider screen for liver damage.

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