AST Blood Test: Purpose, Preparation, Procedure, and Results

Aspartate aminotransferase (AST) is one of the key liver enzymes that help assess liver health. Liver blood tests measure it to detect symptoms of liver damage or injury.

When liver cells are damaged, AST leaks into the bloodstream, increasing its levels.

Your healthcare provider may order liver function tests for the evaluation of liver function and to determine the type of liver damage, aiding in diagnosis and treatment.

What is an AST test?

An AST test measures the level of aspartate aminotransferase (AST) in your blood.

AST is an enzyme (a type of protein) found mostly in the liver but also in the heart, muscles, kidneys, and brain. It helps convert amino acids into energy.

The AST test helps doctors understand how well these organs are functioning by checking the level of AST in your blood.

Other names for the AST test include:

• SGOT test

• Serum glutamic oxaloacetic transaminase test

• Aspartate transaminase test.

What is it used for?

The AST blood test is a key part of liver tests, helping doctors assess your liver condition.

This test is mainly used to check on the health of your liver and find possible liver issues or disease.

However, since AST is also found in other organs like the heart and muscles, the test can also help diagnose muscle injuries or heart conditions.

Why do I need an AST blood test?

You may need an AST blood test if your doctor suspects you have liver damage, muscle injury, or another condition affecting organs that produce AST.

Common reasons for an AST test

i) Symptoms of liver disease

If your doctor believes you might have problems related to your liver, he may recommend you get an AST test done. Some of these signs could be:

• Jaundice (yellow skin or eyes)

• Dark urine or pale stool

• Unexplained fatigue or weakness

• Nausea, vomiting, or loss of appetite

• Abdominal pain or swelling (especially in the upper right side)

• Itchy skin

ii) Monitoring liver health

• If you have a medical history of alcohol use disorder, hepatitis, or liver disease

• If you're taking medications that can affect your liver (e.g., statins, antibiotics, or pain relievers like acetaminophen)

• If you have a family history of liver disease

iii) Checking for muscle or heart damage

• If you have symptoms of muscle injury, such as pain, weakness, or dark-coloured urine (a sign of muscle breakdown),

• If your doctor thinks you might have a heart problem (though other tests are usually used for this now).

iv) Part of routine health screening

Some doctors include AST testing as part of a general liver function panel. This testing is common for those at higher risk for liver disease, like people with diabetes, obesity, or high cholesterol.

To take charge of your health, book an appointment with Thomson Medical to meet our medical specialists and discuss a personalised treatment plan.

Will I need to do anything to prepare for the test?

You usually don't need to do anything special to prepare for an AST blood test. However, your doctor may have some guidelines that you will need to follow based on the reason for the test.

General Preparation Guidelines

• Fasting: 

  • In most cases, fasting is not required. However, if the AST test is part of a liver panel or comprehensive metabolic panel (CMP), you may need to fast for 8–12 hours before the test.

• Medications: 

  • Some medications can affect your AST levels. Your healthcare provider might ask you to avoid certain drugs before the test, such as:

• Pain relievers (acetaminophen, ibuprofen, aspirin)

• Statins (cholesterol-lowering drugs)

• Certain antibiotics or anti-seizure medications

• Alcohol: 

  • Avoid alcohol for at least 24 hours before the test, as it can temporarily raise AST levels.

• Exercise: 

  • Intense physical activity can increase AST levels due to muscle breakdown, so it may be best to avoid heavy exercise before the test.

What happens during an AST blood test?

An AST blood test is a simple and quick procedure. Here’s what happens during the test:

i) Preparation:

• You’ll be seated comfortably, and a healthcare provider will clean the area (usually your arm) with an antiseptic.

• An elastic band (tourniquet) is placed around your upper arm to make your veins more visible.

ii) Blood collection:

• A small needle is inserted into a vein, usually in your arm.

• A tube is attached to collect the blood sample. You may feel a slight pinch but usually no significant pain.

iii) Completion:

• Once enough blood is collected, the needle will be removed, and a small bandage will be placed over the site.

• You may be asked to apply gentle pressure at the site of the blood draw to help prevent bruising.

What do the results mean?

• Normal AST levels typically range from 10 to 40 units per litre (U/L), though the number can vary depending on the lab.

• High AST levels may suggest liver disease (e.g., shock liver, liver cancer), a heart attack, muscle damage, or other health conditions.

• Low AST levels are generally not a cause for concern and usually don’t indicate any health problems.

Are there any risks to the test?

An AST blood test is a very safe procedure with minimal risks. However, like any blood test, there are some minor side effects to be aware of:

• Slight pain or discomfort: 

  • You might feel a small pinch when the needle is inserted into your vein.

• Bruising or swelling: 

  • A small bruise may form at the needle site, but it usually fades within a few days.

• Bleeding: 

  • Some individuals may bleed a little longer than usual, especially if they have a blood clotting disorder or are taking blood thinners.

• Dizziness or lightheadedness: 

  • Rarely, people may feel faint after having blood drawn. If this happens, resting for a few minutes usually helps.

• Infection (very rare): 

  • There is a slight risk of infection if the skin isn’t thoroughly cleaned, but the scenario is extremely uncommon.

FAQ

Is it better to have high or low AST?

In general, neither high nor low AST levels are ideal—you want them to be within the normal range. High AST is usually more concerning because it can indicate liver or muscle damage. Low AST is rarely a problem unless accompanied by other abnormal test results. The most important thing is to look at AST in combination with ALT (alanine aminotransferase) and other tests to determine the underlying cause.

What does a high AST level mean?

A high AST level is typically a sign of liver damage, muscle injury, or heart problems.

What level of AST is alarming?

The information provided is intended for general guidance only and should not be considered medical advice. For personalised recommendations based on your medical conditions, request an appointment with Thomson Medical.