Also Known As
Serum glutamic-pyruvic transaminase (SGPT)
Formal Name
Alanine aminotransferase
This article was last reviewed on
This article waslast modified on
22 April 2018.
At a Glance
Why Get Tested?

To screen for liver disease

When To Get Tested?

If your doctor thinks that you have symptoms of a liver disorder

Sample Required?

A blood sample taken from a vein in your arm

Test Preparation Needed?

No test preparation is needed, although you should inform your doctor about any drugs you are taking

On average it takes 7 working days for the blood test results to come back from the hospital, depending on the exact tests requested. Some specialist test results may take longer, if samples have to be sent to a reference (specialist) laboratory. The X-ray & scan results may take longer. If you are registered to use the online services of your local practice, you will be able to access your results online.

If the doctor wants to see you about the result(s), you will be offered an appointment. If you are concerned about your test results, you will need to arrange an appointment with your doctor so that all relevant information including age, ethnicity, health history, signs and symptoms, laboratory and other procedures (radiology, endoscopy, etc.), can be considered.

Lab Tests Online-UK is an educational website designed to provide patients and carers with information on laboratory tests used in medical care. We are not a laboratory and are unable to comment on an individual's health and treatment.

Reference ranges are dependent on many factors, including patient age, gender, sample population, and test method, and numeric test results can have different meanings in different laboratories.

For these reasons, you will not find reference ranges for the majority of tests described on this web site. The lab report containing your test results should include the relevant reference range for your test(s). Please consult your doctor or the laboratory that performed the test(s) to obtain the reference range if you do not have the lab report.

For more information on reference ranges, please read Reference Ranges and What They Mean.

What is being tested?

ALT is an enzyme found mostly in the liver; smaller amounts are also found in the kidneys, heart, and muscles. When the liver is damaged, ALT is released into the bloodstream, hence increasing the concentration that can be detected in a blood test. This often happens before more obvious symptoms of liver damage occur, such as jaundice (yellowing of the eyes and skin).

How is the sample collected for testing?

A blood sample will be taken from a vein in the arm.

Is any test preparation needed to ensure the quality of the sample?

No test preparation is needed, although you should inform your doctor about any drugs you are taking.

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Common Questions
  • How is it used?

    The ALT blood test detects liver injury. ALT results are usually assessed alongside the results of other blood tests such as alkaline phosphatase (ALP), gamma-glutamyl transferase (GGT) and aspartate aminotransferase (AST), to help determine which form of liver disease is present.

  • When is it requested?

    A doctor usually requests an ALT test with other laboratory investigations to evaluate a patient who has symptoms of a liver disorder. ALT is used to identify liver damage. Some of these symptoms include jaundice, dark urine, nausea, vomiting, abdominal swelling, unusual weight gain, and abdominal pain. ALT can also be used, either by itself or with other tests, for patients at risk of developing liver disease such as:

    • persons who have a history of known or possible exposure to hepatitis viruses,
    • those who drink too much alcohol,
    • those whose family have a history of liver disease,
    • people who take drugs that might damage the liver
    • those who are overweight or who have diabetes

    In people with mild symptoms, such as tiredness or loss of energy, ALT may be tested to make sure they do not have chronic (long-term) liver disease. ALT is often used to monitor the treatment of persons who have liver disease, to see if the treatment is working, and may be requested either by itself or along with other blood tests.

  • What does the test result mean?

    Very high concentrations of ALT (more than 10 times the highest normal level) are usually due to acute (short-term) hepatitis, often due to a viral infection. In acute hepatitis, the concentration of ALT usually stays high for about 1–2 months, but can take as long as 3–6 months to return to normal. 

    ALT concentrations are usually not as high in chronic hepatitis, often less than 4 times the highest normal level: in this case, ALT levels often vary between normal and slightly increased, so doctors may request the test frequently to see if there is a pattern. A moderately high ALT can also occur occasionally when there is a high alcohol intake, diabetes or raised serum triglycerides, all of which can cause fatty liver.

    In some liver diseases, especially when the bile ducts are blocked (cholestasis), when a person has cirrhosis, or when liver cancer is present, the concentration of ALT may be close to normal.

  • Is there anything else I should know?

    An injection of medicine into the muscle tissue, or strenuous exercise, may increase ALT concentration.

    Certain drugs may raise the concentration of ALT in the bloodstream by causing liver damage. This occurs in a very small percentage of patients, and is true of both prescription drugs and some 'natural' health products. If your doctor finds that you have a high ALT, tell him or her about all the drugs and health products you are taking.

  • What is hepatitis?

    Hepatitis is an inflammation of the liver.  There are two major forms: acute and chronic.  Acute hepatitis is a fast developing disease and typically makes affected persons feel sick, as if they have the flu, often with loss of appetite and sometimes diarrhoea and vomiting.  In many cases, acute hepatitis turns urine brown, makes stools pale, and colours the skin and eyes yellow.  Most affected individuals eventually recover completely. Chronic (long-term) hepatitis usually causes no symptoms, or causes only loss of energy and tiredness; most people don’t know that they have it. In some people, chronic hepatitis can gradually damage the liver and, after many years, cause it to fail.

  • What are the other liver tests?

    Other commonly used liver tests include other enzymes found in liver cells, such as aspartate aminotransferase (AST) and alkaline phosphatase, as well as bilirubin which is a breakdown product from red blood cells removed from the body by the liver and spleen. Albumin is also frequently included in the liver test profile because as albumin is produced by the liver it can be used as a measure of liver protein synthesis. However, other factors can affect the concentration of albumin in the blood such as poor nutrition or excessive loss from the gut or kidney. The doctor will often order these tests together as a group and refer to them as 'liver function tests'.