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Summary
What is AST?
Aspartate aminotransferase (AST) is an enzyme found mostly in the liver but also in red blood cells, heart and other muscles. If your liver, red blood cells, heart or muscle cells are injured they release AST into the blood. Normally, you have low levels of AST in your blood. When your liver or other cells that contain AST are damaged, they release AST. This can lead to high AST levels in your blood.
Why get tested?
AST is typically measured as part of Liver Function Tests (LFTs). This is a standard group of tests that is routinely used to check the health of the liver.
LFTs measure enzymes and proteins that are either produced by the liver cells as part of its normal function or released into the blood when liver cells are damaged. Looked at together, along with your symptoms and medical history, they help build a picture of your liver’s health. Either higher or lower than normal levels of these substances can indicate a problem with your liver.
As well as AST, they measure the enzymes gamma-glutamyl transferase (GGT), alanine transaminase (ALT), bilirubin (a breakdown product from red blood cells that is removed from the body by the liver) and albumin (the most common protein in your blood which is made by your liver).
Liver damage
Testing for AST is usually done to detect liver damage. While many things can harm the liver, the major causes of liver disease are infections that target the liver, drinking too much alcohol and obesity. Some inherited diseases can damage the liver. Also, some medicines can harm the liver. Your doctor may suggest testing your liver from time to time if you are taking a medication that is known to do this.
Acute and chronic hepatitis
Hepatitis is an inflammation of the liver. There are two major forms: acute and chronic.
| Acute Hepatitis | This is fast-developing and typically makes you feel very ill. In many cases, acute hepatitis causes jaundice - when skin and eyes become yellow and your urine turns brown. It is usually a short term illness. Hepatitis A virus is the most common cause of acute hepatitis. It can also be caused by drugs, alcohol, immune system conditions, and any condition that stops bile being released from your liver. Liver diseases that occur during pregnancy can cause acute hepatitis. |
| Chronic Hepatitis | This is when liver inflammation lasts longer than six months. It usually causes few or no symptoms - typically a loss of energy and tiredness. Most people don’t know that they have it. Chronic hepatitis gradually damages the liver, and this can slowly progress to fibrosis (scarring) and eventually to cirrhosis or liver failure. Chronic hepatitis is usually caused by hepatitis B or C infection but alcoholic liver disease (ALD) and metabolic-dysfunction fatty liver disease (MAFLD), are also major causes. |
Having the test
Sample
Blood.
Any preparation?
None.
Your results
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.
| Condition | Possible AST results |
| Acute hepatitis | Very high levels of AST (more than 10 times the highest normal level) are usually due to a rapidly developing liver disease (acute hepatitis) which is often due to a viral infection. In acute hepatitis, AST levels usually stay high for about one to two months, but they can take as long as three to six months to return to normal. |
| Chronic hepatitis | In slowly developing liver disease (chronic hepatitis), AST levels are usually not as high - often less than four times the highest normal level. In chronic hepatitis, AST often varies between normal and slightly increased. If this is the case, your doctors may request the test regularly to determine the pattern of change. |
| Bile duct blockages | AST may be close to normal in some diseases of the liver especially when the bile ducts are totally or partially blocked, or in cirrhosis. |
| Alcohol | When liver damage is due to alcohol, AST often increases much more than ALT (this is a pattern that is not seen with most other liver diseases). |
| Medications | Some medicines can damage the liver thereby increasing AST levels. This is true of both prescription medicines and some 'natural' or ‘alternative’ health products. It is important to let your doctors know about any medicines and health products you are taking. |
| Muscle and red blood cell breakdown | AST levels can also be increased because of the break-down of red blood cells (haemolysis). This can happen after heart attacks and when you have muscle injury. An injection into muscle tissue, or even strenuous exercise, may increase AST levels due to release of AST from the muscle. |
Reference intervals
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.
| AST reference intervals | |
| Adult male | 5 - 35 U/L |
| Adult female | 5 - 30 U/L |
| The reference intervals for this test are common reference intervals which means that all laboratories in Australia should be using this same target range. | |
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:
More information
Pathology and diagnostic imaging reports can be added to your My Health Record. You and your healthcare provider can now access your results whenever and wherever needed.
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