Alanine Aminotransferase (ALT)- Pathology

Alanine transaminase test evaluates liver damage. This test can help your doctor determine whether a condition, medication, or injury has harmed your liver.

ALT is typically not examined in isolation. Instead, it is generally tested together with other liver enzymes in a panel test like the liver panel or complete metabolic panel (CMP).

Understanding Alanine Transaminase (ALT)

Alanine aminotransferase, also known as alanine transaminase (ALT),  is an enzyme primarily located in your liver. However, it can also be found in other parts of the body. ,  The liver uses this enzyme to transform food into energy.

An enzyme is a specific kind of protein found in cells that functions as a catalyst and enables specific physiological processes. Your body has a large number of enzymes that serve essential purposes.

What Does The ALT Test Measure?

The ALT in your blood is determined via a blood test, which is called an ALT test. Healthcare professionals frequently utilize an ALT blood test to help determine your liver's health since elevated ALT levels in the blood can occur when the liver is damaged.

Healthcare professionals do not use the test alone to make diagnoses because a variety of liver issues can raise ALT levels. A blood tests panel, such as a liver enzyme panel (HFP or LFT) or a complete metabolic panel (CMP), will frequently include an ALT blood test. A blood panel can provide more precise information about your general health by measuring multiple components of your blood with a single sample.

Other common names for an ALT blood test include:

  • GPT.
  • Alanine aminotransferase.
  • Serum glutamic-pyruvic transaminase.
  • SGPT.

Why Would My Doctor Order This Test?

Your doctor might advise testing your ALT level if you show any of the following symptoms of liver disease or damage:

  • Nausea
  • Vomiting
  • Abdominal (belly) pain or swelling
  • Yellow eyes or skin (a condition called jaundice)
  • Extreme tiredness (fatigue)
  • Weakness
  • Light-colored poop
  • Dark-colored urine
  • Itchy skin

You might undergo this test for the following reasons:

  • You have come into contact with the hepatitis virus
  • You consume a lot of alcohol
  • You have a history of liver illness in your family
  • You take a drug that's known to cause liver damage

Purpose Of The ALT Test

An ALT blood test is used to assess the condition of your liver. An ALT blood test can help identify liver problems since ALT can seep into your blood if your liver's cells are damaged.


Screening involves looking for any medical problems before you notice any symptoms. For example, if you have any of the following risk factors for liver disease, your doctor may advise screening with a liver panel blood test that includes an ALT test:

  • Family history of liver disease
  • Heavy alcohol use
  • Obesity
  • Diabetes
  • Injecting drugs using shared needles

You could undergo an ALT test even if you are not at risk of developing liver disease because ALT tests are frequently included in routine blood panel exams that evaluate your general overall health, like a CMP.


If you have a liver disorder, your doctor might request an ALT test, as part of a panel, to track your status and determine if it is getting better, getting worse, or remaining the same with or without medication. If you take a medicine that may harm your liver, your doctor may additionally order an ALT test and a panel of liver enzymes.


When you show symptoms that could indicate liver disease, your doctor may order an ALT test to make a diagnosis. While ALT levels alone cannot be used to identify an illness, they can play a significant role.

The symptoms and signs of liver disease include the following:

  • Nausea
  • Vomiting
  • Itchy skin
  • Abdominal pain
  • Jaundice
  • Fatigue
  • Appetite loss

When Should I Get An ALT Test?

ALT testing is appropriate in a variety of medical situations. For example, if you experience symptoms related to a liver condition, it is frequently recommended as a preliminary diagnostic test.

A panel test that includes ALT may be employed in the diagnosis process, even if you only have nonspecific symptoms. For example, an essential evaluation in urgent care or the emergency room may include the liver panel or CMP, which includes ALT.

Even if you do not have any symptoms, you should routinely have your ALT and other liver enzymes evaluated as a tool for the early detection of liver disease. Your doctor may suggest ALT screening if you are more likely to develop liver disease.

Your routine medical exams may also include an ALT test. Nevertheless,enough evidence to prove that broad screening has more advantages than disadvantages, such as higher medical expenditures and pointless treatments, is currently lacking.

If a previous test had an aberrant result, follow-up ALT testing might be done. Repeated ALT tests help track the development of liver disease if you were  previously diagnosed with the same. In addition, ALT testing might be a technique to keep an eye out for undesirable side effects when your doctor prescribes a drug that may damage your liver.

What Happens During An ALT Blood Test?

Blood draws, including those for an ALT blood test, are often carried out by a healthcare professional known as a phlebotomist. Still, any healthcare professional with training in blood drawing can carry out this task.

The following can be anticipated during a blood test or blood draw:

First, a medical professional will examine your arms as you sit in a chair to see whether a vein can be accessed easily. This is typically on the other side of your elbow, in the inner portion of your arm.

After finding a vein, the area will be cleaned and sanitized. They will then take blood from a vein in your arm using a small needle. It might feel like a tiny pinch.

A tiny amount of blood will accumulate in a test tube after the needle has been inserted. After drawing enough blood to do the test, they will remove the needle and apply gauze or cotton to the wound to stop bleeding.

They cover the site with a bandage, and you will be done. Often, the entire process takes around five minutes.

Once your blood is drawn, the samples are delivered to a facility where a medical laboratory scientist performs the test on analyzers after preparing the samples.

Do I have to fast for an ALT blood test?

You will probably need to fast for 10 to 12 hours before your blood test for the comprehensive metabolic panel and if your ALT test is a component of the CMP. If you are fasting, you will not eat or drink anything besides water.

Although this is uncommon, you do not have to fast if you only have an ALT blood test.

In any case, when they order the bloodwork, your healthcare professional will give you instructions. So be careful to adhere to their instructions.

Is there anything I should do to prepare for an ALT blood test?

Telling your doctor about any medications or dietary supplements you are taking before the test is done is very important because different kinds of drugs and supplements have the potential to alter your ALT levels. Your doctor might ask you to stop using a drug before the test in specific circumstances. Your doctor might also instruct you to discontinue taking certain medications.

When getting the ALT test, let your doctor know whether you often engage in physically demanding workouts because this might also alter your ALT levels.

Can I Take The ALT Test At Home?

There are options for performing ALT testing at home, but doing so in a hospital setting is considerably more common.

Some at-home test kits include a few measurements, including ALT, to assess the liver's health. You can draw blood at home for these tests, but you will need to submit it to a lab to examine it. Most at-home tests do not need a prescription.

What Are The Risks Of The ALT Test?

The ALT blood test is safe. The risks associated are usually minor and can include the following:

  • Bruising
  • Bleeding
  • Infection
  • Fainting or feeling dizzy
  • Slight pain when the needle is inserted

What Do the Results Mean?

You should receive your results In approximately a day. The following details are typically included in blood test reports, including ALT test reports:

  • What was examined in the blood or the name of the blood test
  • Your blood test result is expressed as a number or measurement
  • The normal measurement range for the specific test
  • Information indicating if your result is high, low, normal, or abnormal

The alanine transaminase (ALT) normal range varies from laboratory to laboratory. 7 to 56 U/L (units per liter) is one common reference range for the ALT blood test. Those assigned males at birth often have greater ALT levels than those assigned females.

Mildly high ALT levels may be caused by the following:

  • Alcohol abuse
  • Mononucleosis
  • Cirrhosis
  • Drugs such as aspirin, statins, and some sleep aids

Moderately high ALT levels may be due to the following:

  • Chronic liver disease
  • Cirrhosis
  • Alcohol abuse
  • Kidney damage
  • Blockage of the bile ducts (a tube that travels through the pancreas and into the small intestine to transport bile from the liver and gallbladder) )
  • Heart failure (when it cannot pump enough blood to your body) or heart attack
  • Damage to red blood cells
  • Muscle injury
  • Heat stroke
  • Excess vitamin A

Very high ALT levels can be due to the following:

  • An overdose of drugs such as acetaminophen (Tylenol)
  • Acute viral hepatitis
  • Sepsis
  • Liver cancer

It is crucial to understand that a high ALT test result does not always indicate that you have a medical condition. For example, just 5% of individuals with increased ALT values have serious liver diseases. Your ALT levels may also be influenced by other factors like:

  1. Exercise: Excessive or intense exercise may momentarily raise ALT levels
  2. Medication: Many drugs, including over-the-counter pain relievers like acetaminophen, can impact ALT levels
  3. Gender: Researchers think that hormonal variances influence sex differences in ALT levels
  4. Menstrual cycle: A woman's menstrual cycle might cause an increase or decrease in ALT levels
  5. Age: As people get older, their ALT levels tend to drop
  6. Heritage: According to research, those with Mexican-American ancestry are more likely to have high ALT levels
  7. Body mass index: Many studies have shown a relationship between ALT levels and body mass index (BMI), which may alter how test findings are interpreted in obese individuals

Your healthcare professional will examine several aspects of your health and circumstances while interpreting your ALT findings in addition to the factors mentioned above, such as:

  • Your medical background
  • How low or high are your ALT results
  • The results of other tests are frequently combined with ALT
  • Previous ALT outcomes
  • If you are experiencing symptoms

What does a low alanine transaminase (ALT) level indicate?

A lower-than-average ALT result is uncommon and typically not cause for alarm. A lower-than-normal ALT level, however, may be a sign of chronic renal illness or a vitamin B6 deficiency.

Your doctor will probably have you retake the test or undergo additional testing if your ALT test results are lower than what is regarded as normal to rule out any underlying medical conditions.

What More Tests Will I Take?

ALT is typically administered as a component of a liver panel, a collection of liver function tests.

A test for aspartate aminotransferase (AST) is also included in this panel. AST is frequently tested in addition to AST in a comprehensive metabolic panel or liver function panel. When specific cells are damaged, these enzymes may leak into your bloodstream.

While AST and ALT are frequently referred to as liver enzymes, AST is more abundant in other organs such as the heart, skeletal muscles, and pancreas. Because of this, ALT is thought to be more closely associated with your liver function, but medical professionals utilize both values to evaluate your liver health.

Your doctor can understand more about the condition of your liver by comparing the levels of ALT and AST in your blood. Your doctor can determine the extent of the liver damage and potential causes using the ALT-to-AST ratio.

Your doctor may also check the levels of additional enzymes and proteins that are present in your liver to determine the sort of liver disease you have, such as:

  • Alkaline phosphatase
  • Albumin
  • Lactate dehydrogenase (LDH)
  • Bilirubin
  • Total protein

Should I Get Additional Testing If My ALT Values Are Abnormal?

If you have an abnormal ALT level, healthcare professionals frequently advise that you undergo additional testing.

Further testing could consist of the following:

  • Repeat the blood tests for ALT
  • Additional blood testing
  • Image-based tests
  • Biopsy

If your ALT levels are noticeably elevated, or you are exhibiting liver problem symptoms, further testing might be necessary immediately.

There is no one follow-up testing strategy that works for everyone because every person and circumstance is different. You and your provider will decide on the ideal strategy together.

When Should I Call My Doctor?

Call your doctor if you have any signs of liver damage, such as jaundice or abdominal pain. Likewise, contact your provider if you have a liver problem or are exhibiting new or worrisome symptoms.

Ask your provider questions if you have any concerns regarding your ALT results. Be sure you comprehend your liver test results by speaking with your doctor. Additionally, learn how these findings might impact your treatment.


  • Moriles KE, Azer SA. Alanine Amino Transferase. [Updated 2022 Dec 10]. In: StatPearls [Internet]. Treasure Island (FL): StatPearls Publishing; 2023 Jan-. Available from:

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