Aspartate-aminotransferase (AST, SGOT)

What is the AST blood test?

An AST blood test measures the amount of aspartate transferase in your blood. In most cases, your healthcare provider uses an AST blood test to help assess the health of your liver, but it can provide insight into other health conditions as well.

Common names for an AST blood test include:

→ Aspartate transferase (AST).

→ Aspartate aminotransferase (AST).

→ Serum glutamic-oxaloacetic transaminase.

→ SGOT.

→ Aspartate transaminase.

What is Aspartate transferase (AST)?

Aspartate transferase (AST), also known as aspartate aminotransferase, is an enzyme that exists in your liver, heart, brain, pancreas, kidneys, muscles and many tissues in your body. Although it can be found throughout your body, AST is most commonly associated with liver health. When cells that contain AST are damaged, they release the AST into your blood. 

What are enzymes?

An enzyme is a type of protein in a cell that acts as a catalyst and allows certain bodily processes to happen. There are thousands of different enzymes throughout your body that have important functions.

Why test AST?

When your cells get damaged, AST can leak into your bloodstream. Because of this, high levels of AST in a blood sample can be a sign of an underlying medical condition — most often (but not always), a liver condition. An AST blood test measures the amount of AST in your blood. The test is commonly used to help diagnose liver damage or disease.

As many types of liver conditions can cause AST levels in your blood to rise, healthcare providers don’t use the test alone to diagnose conditions. An AST blood test is most often included in a blood test panel, such as a liver enzyme panel (HFP) or a Comprehensive Metabolic Panel (CMP). A blood panel measures several aspects of your blood with one sample and can provide more detailed information about your overall health.

Why do I need an AST blood test?

You may get an AST blood test as part of your routine checkup (see CMP) or if you have symptoms of liver damage. 

These liver damage symptoms may include:

→ Nausea and vomiting

→ Lack of appetite

→ Fatigue

→ Weakness

→ Jaundice, a condition that causes your skin and eyes to turn yellow

→ Swelling and/or pain in your abdomen (belly)

→ Swelling in your ankles and legs

→ Dark-colored urine (pee) and/or light-colored stool (poop)

→ Frequent itching

Even if you don't have symptoms, your health care provider may order an AST blood test if you're more likely to develop liver disease because of:

→ A family history of liver disease

→ Alcohol use disorder

→ Obesity

→ Diabetes

→ Taking certain medicines that can cause liver damage

→ Hepatitis or exposure to hepatitis

AST and your liver:

Your liver is an organ that has many important jobs: 

→ It makes a fluid called bile that helps your body digest food. 

→ It also removes waste products and other toxins from your blood.

→ It produces proteins, as well as substances that help your blood clot. 

Alcohol or drug use and diseases such as hepatitis can damage your liver and keep it from doing these jobs.

AST is an enzyme your liver makes. Other organs, like your heart, kidneys, brain, and muscles, also make smaller amounts. AST is also called SGOT (serum glutamic-oxaloacetic transaminase).

Normally, AST levels in your blood are low. When your liver is damaged, it puts more AST into your blood, and your levels rise.

A high AST level is a sign of liver damage, but it can also mean you have damage to another organ that makes it, like your heart or kidneys. That's why doctors often do the AST test together with tests of other liver enzymes.

When cells become damaged, AST can be released into the bloodstream. For this reason, abnormal levels of AST in a blood sample can indicate an underlying problem.

Although AST can be measured alone, it is usually included with other enzymes as part of broader tests, such as a liver panel or comprehensive metabolic panel (CMP). When interpreted alongside other enzymes, an AST measurement can help identify liver disease and other health issues.

To understand the significance of your results, your doctor often looks at AST and the levels of other enzymes included in a liver panel test. Patterns in which enzymes are normal or abnormal can offer meaningful clues about an underlying problem.

Because AST levels in the blood can rise when cells are damaged, elevated AST can reflect health conditions, including liver diseases like cirrhosis or hepatitis. To determine the cause of an abnormal result, the doctor may consider how high the AST level is and how it compares to the levels of other liver enzymes.

Very high levels of AST often reflect short-term liver damage, while smaller but persistent elevations in AST over time can be tied to chronic conditions. However, because AST is found in other body parts, it can be elevated in the blood due to cell damage outside the liver.

For this reason, the doctor may look at the levels of both AST and the enzyme alanine aminotransferase (ALT) side by side. ALT is more concentrated in the liver, so if AST is high while ALT is normal, it can indicate a problem outside the liver. In other cases, though, having a much higher level of AST than ALT can be a sign of alcohol-induced damage to the liver.

It is also important to note that having elevated AST is not proof of a medical problem. If you are healthy with proper liver function, you may still have an AST level outside the normal range, which can occur based on individual factors like age, sex, race, diet, exercise, or having taken medications that can affect AST.

What is the normal range for an AST blood test?

The normal range for aspartate transferase (AST) varies from laboratory to laboratory. One common reference range for an AST blood test is 8 to 33 U/L (units per liter). As ranges can vary depending on the laboratory, it’s important to check your test result report to see what your specific lab’s reference range is.

It’s also important to know that there’s no AST range that’s normal for all people. A healthy AST level can change depending on several factors, including:

→ Your age.

→ Your sex.

→ Your race.

→ Your weight.

AST levels are usually listed on your test report in units per liter (U/L) or international units per liter (IU/L). Next to the level found in your blood, the test report should list the laboratory’s reference range.

It is important to look closely at the range for the specific lab that analyzed your sample because there is no universal reference range for AST. Ranges can vary because not all labs use the same methods, and studies have not demonstrated a precise healthy range.

In addition, no AST level is normal for all people. Instead, a healthy AST level can change depending on your age, sex, race, weight, and other factors that your doctor can consider when interpreting your test result.

If your results are not in the normal range, it doesn't always mean that you have a medical condition that needs treatment. Many things can affect your results, such as certain medicines and your age, sex, and diet.

References:

Huang XJ, Choi YK, Im HS, Yarimaga O, Yoon E, Kim HS. Aspartate Aminotransferase (AST/GOT) and Alanine Aminotransferase (ALT/GPT) Detection Techniques. Sensors (Basel). 2006 Jul 31;6(7):756–82. PMCID: PMC3894536.

Purcell GV, Behenna DB, Walsh PR. Alanine aminotransferase and aspartate aminotransferase measurements with two automated analyzers, SMAC and the ABA-100, compared. Clin Chem. 1979 May;25(5):780-2. PMID: 436250.

Sookoian S, Pirola CJ. Liver enzymes, metabolomics and genome-wide association studies: from systems biology to the personalized medicine. World J Gastroenterol. 2015 Jan 21;21(3):711-25. doi: 10.3748/wjg.v21.i3.711. PMID: 25624707; PMCID: PMC4299326.

Lala V, Zubair M, Minter DA. Liver Function Tests. [Updated 2023 Apr 7]. In: StatPearls [Internet]. Treasure Island (FL): StatPearls Publishing; 2023 Jan-. Available from: https://www.ncbi.nlm.nih.gov/books/NBK482489/

Dufour DR, Lott JA, Nolte FS, Gretch DR, Koff RS, Seeff LB. Diagnosis and monitoring of hepatic injury. I. Performance characteristics of laboratory tests. Clin Chem 2000;46(12):2027-49.

Dufour DR, Lott JA, Nolte FS, Gretch DR, Koff RS, Seeff LB. Diagnosis and monitoring of hepatic injury. II. Recommendations for use of laboratory tests in screening, diagnosis, and monitoring. Clin Chem 2000;46(12):2050-68.

Dufour DR. Effects of habitual exercise on routine laboratory tests [abstract]. Clin Chem 1998;44 (Suppl 6):A136.

Narjes H, Nehmiz G. Effect of hospitalisation on liver enzymes in healthy subjects. Eur J Clin Pharmacol 2000;56(4):329-33.