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:
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.
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.
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.
This article was last reviewed on 21 March 2017. | This article was last modified on 21 March 2017.
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