Alanine aminotransferase (ALT) is an enzyme found mostly in the liver. Smaller amounts are also found in the kidneys, heart and muscles. The ALT test measures the amount of the enzyme in your blood. Normally, ALT levels are low but when the liver cells are damaged they release ALT into the bloodstream. This usually occurs before more obvious symptoms of liver damage can be seen. ALT is typically measured as part of a group of tests that reflect the condition of the liver known as Liver Function Tests (LFTs). These are all performed on the same blood sample and they give information about how your liver is working.
Why get tested?
A Liver Function Tests (LFTs) panel is ordered to assess the condition of the liver in someone who has symptoms of a liver disorder. LFTs measure the levels of several different substances in the blood that are either produced by the liver cells as part of its normal function or released into the blood when liver cells are damaged.
Measuring ALT levels is the best way to test for liver damage. Some conditions that can cause elevations in ALT are hepatitis (liver inflammation), nonalcoholic fatty liver disease, heart failure, cancer and the effects of some drugs such as large doses of paracetamol.
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 someone who has liver disease to see if the treatment is working and it may sometimes be ordered by itself.
Having the test
Reading your test report
Your results will be presented along with those of your other tests on the same form. You will see separate columns or lines for each of these tests.
Very high levels of ALT (more than 10 times the highest normal level) are usually due to acute (short-term) hepatitis (inflammation of the liver). It is often due to a virus infection. In acute hepatitis ALT levels usually stay high for about 1–2 months but they can take as long as 3–6 months to return to normal.
ALT levels are usually not as high in chronic hepatitis, often less than four times the highest normal level. In this case, ALT levels often vary between normal and slightly increased so doctors will order the test frequently to see if there is a pattern.
In some liver diseases, especially when the bile ducts are blocked or when a person has cirrhosis ALT may be close to normal levels.
Certain medications and health products may raise ALT levels by causing liver damage in a very small percentage of people taking them. This is true of both prescription drugs and some ‘natural’ health products. If your doctor finds that you have a high ALT, tell them about all the drugs and health products you are taking.
Your results will be compared to reference intervals (sometimes called a normal range).
If your results are flagged as high or low this does not necessarily mean that anything is wrong. It depends on your personal situation. Your results need to be interpreted by your doctor.
ALT Reference Intervals
The reference intervals for this test are common reference intervals which means that all laboratories in Australia should be using this same target range.
Male 5 - 40 U/L
Female 5 - 35 U/L
Questions to ask your doctor
The choice of tests your doctor makes will be based on your medical history and symptoms. It is important that you tell them everything you think might help.
You play a central role in making sure your test results are accurate. Do everything you can to make sure the information you provide is correct and follow instructions closely.
Talk to your doctor about any medications you are taking. Find out if you need to fast or stop any particular foods or supplements. These may affect your results. Ask:
Anymore to know?
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 someone 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 and colours the skin and eyes yellow. Most people who are affected eventually recover completely.
Chronic (long-term) hepatitis usually causes no symptoms or causes only loss of energy and tiredness - most people don’t know they have it. In some people chronic hepatitis can gradually damage the liver and, after many years, cause it to fail.
Other commonly used liver tests include other enzymes found in liver cells such as aspartate aminotransferase (AST), gamma-glutamyl transferase (GGT) and alkaline phosphatase (ALP), as well as bilirubin (a breakdown product from red blood cells removed from the body by the liver and spleen) and albumin (a protein produced by the liver). These will be ordered together as a group liver function tests and performed on the same blood sample.
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