Summary

Aspartate aminotransferase (AST) is an enzyme found mostly in the liver but also in red blood cells, heart and other muscles. When liver, red blood cells, heart or muscle cells are injured they release AST into the blood.

AST can be measured by itself but more often it is measured as part of a group of tests 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?

The AST test can be ordered by itself but more often as one in the panel of tests known as Liver Function Tests (LFTs) if you have symptoms that suggest 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 their normal function or released into the blood when liver cells are damaged.

They include gamma-glutamyl transferase (GGT) alanine transaminase (ALT), alkaline phosphatase (ALP), 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). By considering the levels of each substance in the context of the others it’s possible to decide which form of liver disorder someone has.  

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.

• 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 elevated for about one to two months but can take as long as three to six months to return to normal. 
• In the slowly developing form of liver disease called 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.
• AST may be close to normal in some diseases of the liver especially when the bile ducts are totally or partially blocked or with cirrhosis. 
• 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). 
• Some medicines can damage the liver thereby increasing AST levels. This is true of both prescription medicines and some 'natural' health products. If your doctor finds that you have high levels of AST, tell them about all the medicines and health products you are taking. 
• As well as rising in liver disease, AST levels can be increased from the break-down of red blood cells (haemolysis). They rise 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). 

• Reference intervals are the range of results expected in healthy people. 
• When compared against them your results may be flagged high or low if they sit outside this range.
• Many reference intervals vary between labs so only those that are standardised or harmonised across most laboratories are given on this website.

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

The reference intervals for this test are common reference intervals which means that most laboratories in Australia should be using this same target range.

Adult

Male   5 - 35 U/L

Female 5 - 30 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:

• Why does this test need to be done?
• Do I need to prepare (such as fast or avoid medications) for the sample collection?
• Will an abnormal result mean I need further tests?
• How could it change the course of my care?
• What will happen next, after the test?

Any more 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 you feel sick, as if you 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 or very few symptoms such as 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.

While many things can harm the liver, the major causes of liver disease are infection by viruses that target the liver, drinking too much alcohol, and obesity with diabetes . Medicines can also damage the liver. Your doctor may suggest testing your liver from time to time if you are taking a medication that puts you at higher risk of liver damage. Some inherited diseases can occasionally damage the liver.

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. Get further trustworthy health information and advice from healthdirect.