An alanine aminotransferase (ALT) test measures the level of ALT in your blood. ALT is an enzyme that is found mostly in the liver.
The liver is the body’s largest gland. It has several important functions, including:
. Making proteins
. Storing vitamins and iron
. Removing toxins from your blood
. Producing bile, which aids in digestion
Proteins called enzymes help the liver break down other proteins so your body can absorb them more easily. ALT is one of these enzymes. It plays a crucial role in metabolism, the process that turns food into energy.
ALT is normally found inside liver cells. However, when your liver is damaged or inflamed, ALT can be released into your bloodstream. This causes serum ALT levels to rise. Many times an increase in ALT is the first sign of a problem and is elevated before other symptoms start to appear.
Measuring the level of ALT in a person’s blood can help doctors evaluate liver function or determine the underlying cause of a liver problem. The ALT test is often part of an initial screening for liver disease.
An ALT test is also known as a serum glutamic-pyruvic transaminase (SGPT) test or an alanine transaminase test.
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Before ALT Test
Why it’s used
The ALT test is usually used to determine whether someone has liver injury or failure. Your doctor may order an ALT test if you’re having symptoms of liver disease, including:
. Jaundice, which is yellowing of your eyes or skin
. Dark urine
. Pain in the right upper quadrant of your abdomen
Liver damage generally causes an increase in ALT levels. The ALT test can evaluate the levels of ALT in your bloodstream, but it can’t show how much liver damage there is or how much fibrosis, or scarring, is present.
The test also can’t predict how severe the liver damage will become.
An ALT test is often done with other liver enzyme tests. Checking ALT levels along with levels of other liver enzymes can provide your doctor with more specific information about a liver problem.
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An ALT test may be part of a routine checkup or requested if someone has risk factors for liver disease, including:
. Family history
. Heavy alcohol use
. Exposure to hepatitis
. Taking certain medications
Other reasons to perform an ALT test include:
. Monitoring the progression of liver diseases, such as hepatitis or liver failure
. Assessing whether treatment for liver disease should be started
. Evaluating how well treatment is working
Before the test
How do I prepare for an ALT 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 and cannot drink anything besides water.
When ALT is tested alone, fasting is not necessary. For this reason, you should 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, you should tell your doctor about any drugs or dietary supplements that you are taking. In some cases, you may be told to stop taking a medication before the test.
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.
Risks and Complications
What are the risks associated with an ALT test?
An ALT is a simple blood test with few risks. Bruising can sometimes occur in the area where the needle was inserted. The risk of bruising can be minimized by applying pressure to the injection site for several minutes after the needle is removed.
In very rare cases, the following complications can occur during or after an ALT test:
. Excessive bleeding where the needle was inserted
. An accumulation of blood beneath your skin, which is called a hematoma
. Lightheadedness or fainting at the sight of blood
. An infection at the puncture site
During ALT Test
How is an ALT test performed?
An ALT test involves taking a small sample of blood, as outlined here:
After ALT Test
After the test
A blood draw is a common and routine procedure that usually has few side effects. A bandage is normally 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 with you 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. After obtaining your blood sample, you will need to 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. You can also normally 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, keep in mind that 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, and in most cases, high ALT is not a sign of severe liver disease.
In order 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 be a sign of 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 that affect the interpretation of your ALT test and what your results mean for your overall health.
What do my ALT test results mean?
. Normal results
According to the American College of Gastroenterology, the normal value for ALT in blood for people without risk factors for liver disease ranges from 29 to 33 international units per liter (IU/L) for males and 19 to 25 IU/L for females. This value can vary depending on the lab.
This range can be affected by certain factors, including sex and age. It’s important to discuss your specific results with your doctor.
. Abnormal results
Higher-than-normal levels of ALT can indicate liver damage. Increased levels of ALT may be a result of:
. Hepatitis, which is an inflammatory condition of the liver
. Cirrhosis, which is severe scarring of the liver
. Death of liver tissue
. A tumor or cancer in the liver
. A lack of blood flow to the liver
. Hemochromatosis, which is a disorder that causes iron to build up in the body
. Mononucleosis, which is an infection usually caused by the Epstein-Barr virus
Most lower ALT results indicate a healthy liver. However, studies have shown that lower-than-normal results have been related to increased long-term mortality. Discuss your numbers specifically with your doctor if you’re concerned about a low reading.
If your test results indicate liver damage or disease, you may need more testing to determine the underlying cause of the problem and the best way to treat it.
Do I need follow-up tests?
Follow-up tests are common if an abnormal level of ALT was found on your liver panel or comprehensive metabolic panel test. Further testing may be immediate if you have significantly elevated ALT and/or symptoms of a problem affecting your liver. This follow-up testing may be more thorough and include blood tests, imaging, and in some cases a biopsy.
After an initial abnormal ALT test, repeat testing may be recommended shortly after your first test or at a later date. A series of tests over time may provide a more robust assessment of your liver health and can sometimes avoid the need for more costly or invasive testing.
The most appropriate follow-up depends on your health situation and the interpretation of your test result, and your physician can review the pros and cons of different options for further testing.