AST

What Is AST?

AST, or aspartate aminotransferase, is one of the so-called liver enzymes, i.e., intracellular enzymes found mainly in the liver, heart muscle, and skeletal muscles. Under normal conditions, they should remain inside the cells; therefore, an increase in their concentration in the blood indicates cell damage, e.g., liver cells.

The liver is responsible for neutralizing toxins and plays a key role in the metabolism of nutrients (e.g., fats). It has a high regenerative capacity, largely dependent on diet. In the diagnostic process of liver diseases, AST levels are measured. The test involves drawing blood from a vein, which is then sent to the laboratory for analysis.

AST Test

The AST test is used in:

• diagnosing liver diseases, such as viral hepatitis A, B, C, alcoholic hepatitis, or fatty liver disease;
• diagnosing heart diseases, e.g., heart attack or myocarditis;
• monitoring the health of patients already diagnosed with liver diseases and during treatment;
• diagnosing skeletal muscle diseases;
• preventive testing, as part of routine blood work, especially in individuals at risk of liver or heart disease.

When Should You Perform an AST Test?

An AST laboratory test is performed when liver damage or disease is suspected, which may present with:

• jaundice;
• itchy skin;
• fatigue, sleepiness;
• loss of appetite;
• weight loss;
• nausea and vomiting;
• pain in the right upper abdomen;
• menstrual disorders in women, including absence of menstruation and even infertility;
• skin changes;
• blood clotting disorders resulting in hemorrhages;
• dark urine and/or pale stools.

The AST test is also recommended for:

• individuals with a family history of liver disease;
• people with alcohol dependence;
• individuals with diabetes;
• people with obesity;
• people taking medications that may cause liver damage.

Elevated AST

Elevated AST may indicate:

Liver damage

• viral hepatitis (acute and chronic);
• alcoholic liver disease;
• toxins and medications causing liver damage;
• fatty liver disease;
• liver cirrhosis.

Heart diseases

• myocardial infarction;
• myocarditis.

Muscle damage

• muscle injuries;
• myositis (muscle inflammation);
• muscular dystrophy.

Autoimmune diseases

• systemic lupus erythematosus;
• autoimmune hepatitis.

Other conditions:

• kidney diseases;
• thyroid disorders;
• cancers;
• hemolysis (breakdown of red blood cells).

Low AST

A low level of aspartate aminotransferase (AST) is rare and generally not concerning.

• during pregnancy, AST levels may be lower due to metabolic changes;
• malnutrition, particularly vitamin B6 deficiency, may lower AST levels;
• people with chronic kidney failure may have reduced AST concentrations;
• thyroid disorders may affect AST levels.

Elevated AST may also be caused by:

• liver damage,
• liver cancer,
• skeletal muscle damage,
• heart muscle damage,
• hepatitis virus infection,
• medications that negatively affect liver function.

Learn more:

• Fatty liver — symptoms, causes, diet
• HCV virus – infection, hepatitis symptoms, and diagnosis of hepatitis C
• Chronic fatigue and lack of energy — causes, symptoms, and treatment

How to Prepare for an AST Test?

The AST test is recommended to be performed in the morning, on an empty stomach — meaning you should refrain from eating for about 12 hours before the test. Drinking a small amount of water in the morning is allowed.

The blood sample should be taken before the morning dose of medication, unless otherwise advised by a doctor. On the day of the test, avoid stress and physical exertion — it is recommended to rest in a seated position for 10–15 minutes before the blood draw.

AST – Reference Range

The reference levels of aspartate aminotransferase (AST) vary depending on age, sex, and the laboratory performing the test. Therefore, results should always be interpreted by a physician.

AST Test Results

The interpretation of AST test results should always take place in the context of other parameters and the patient’s medical history. A key indicator is the ratio of AST to ALT (the de Ritis ratio). In the case of abnormal results, a medical consultation is recommended for proper evaluation.

More information on how to access your test results can be found HERE >>

Factors That May Affect Test Results

• taking certain medications,
• alcohol,
• pregnancy,
• physical activity,
• muscle and liver damage.

Who Should You Consult About Abnormal Results?

• Gastroenterologist
• Internist
• Cardiologist