Davis's Lab & Diagnostic Tests

Aspartate Aminotransferase


AST, SGOT (serum glutamic-oxaloacetic transaminase).

Common Use:
Considered an indicator of cellular damage in liver disease, such as hepatitis or cirrhosis.

Serum collected in a gold-, red-, or red/gray-top tube.

Normal Findings:
(Method: Spectrophotometry, enzymatic at 37°C)

AgeConventional & SI UnitsSI Units Expressed as microkat/L = (Units/L × 0.017)
Newborn25–75 units/L0.43–1.28 microkat/L
10 days–23 mo15–60 units/L0.26–1.02 microkat/L
2–3 yr10–56 units/L0.17–0.95 microkat/L
4–6 yr20–39 units/L0.34–0.66 microkat/L
7–19 yr12–32 units/L0.2–0.54 microkat/L
20–49 yr
 Male20–40 units/L0.34–0.68 microkat/L
 Female15–30 units/L0.26–0.51 microkat/L
Greater than 50 yr (older adult)
 Male10–35 units/L0.17–0.6 microkat/L
Greater than 45 yr (older adult)
 Female10–35 units/L0.17–0.6 microkat/L
Values may be slightly elevated in older adults due to the effects of medications and the presence of multiple chronic or acute diseases with or without muted symptoms.


Aspartate aminotransferase (AST) is an enzyme that catalyzes the reversible transfer of an amino group between aspartate and α-ketoglutaric acid in the citric acid or Krebs cycle, a powerful and essential biochemical pathway for releasing stored energy. AST exists in large amounts in liver and myocardial cells and in smaller but significant amounts in skeletal muscle, kidneys, pancreas, red blood cells, and the brain. Serum AST rises when there is damage to the tissues and cells where the enzyme is found and levels directly reflect the extent of damage. AST values greater than 500 units/L (SI = 8.5 microkat/L) are usually associated with hepatitis and other hepatocellular diseases in an acute phase. AST levels are very elevated at birth, decrease with age to adulthood, and increase slightly in older adults.

This procedure is contraindicated for



  • Compare serially with alanine aminotransferase levels to track the course of hepatitis.
  • Monitor response to therapy with potentially hepatotoxic or nephrotoxic drugs.
  • Monitor response to treatment for various disorders of hepatic function in which AST may be elevated, with tissue repair indicated by declining levels.

Potential Diagnosis

Increased In:

AST is released from any damaged cell in which it is stored, so conditions that affect the liver, kidneys, heart, pancreas, red blood cells, or skeletal muscle, and cause cellular destruction demonstrate elevated AST levels.

Significantly Increased in: (greater than five times normal levels)

  • Acute hepatitis (AST is very elevated in acute viral hepatitis)
  • Acute hepatocellular disease (especially related to chemical toxicity or drug overdose; moderate doses of acetaminophen have initiated severe hepatocellular disease in patients who are alcoholics)
  • Acute pancreatitis
  • Shock

Moderately Increased in: (three to five times normal levels)

  • Alcohol misuse (chronic)
  • Biliary tract obstruction
  • Cardiac dysrhythmias
  • Cardiac catheterization, angioplasty, or surgery
  • Cirrhosis
  • Chronic hepatitis
  • Heart failure
  • HELLP (hemolysis, elevated liver enzymes, low platelet count) syndrome of pregnancy
  • Infectious mononucleosis
  • Liver tumors
  • Muscle diseases (e.g., dermatomyositis, dystrophy, gangrene, polymyositis, trichinosis)
  • Myocardial infarction
  • Reye’s syndrome
  • Trauma (related to injury or surgery of liver, head, and other sites where AST is found)

Slightly Increased in: (two to three times normal)

  • Cerebrovascular accident
  • Cirrhosis, fatty liver (related to obesity, diabetes, jejunoileal bypass, administration of total parenteral nutrition)
  • Delirium tremens
  • Hemolytic anemia
  • Pericarditis
  • Pulmonary infarction

Decreased In:

  • Hemodialysis (presumed to be related to a corresponding deficiency of vitamin B6 observed in hemodialysis patients)
  • Uremia (related to a buildup of toxins which modify the activity of coenzymes required for transaminase activity)
  • Vitamin B6 deficiency (related to the lack of vitamin B6, a required cofactor for the transaminases)

Critical Findings


Interfering Factors

  • Drugs and other substances that may increase AST levels by causing cholestasis include amitriptyline, anabolic steroids, androgens, benzodiazepines, chlorothiazide, chlorpropamide, dapsone, erythromycin, estrogens, ethionamide, gold salts, imipramine, mercaptopurine, nitrofurans, oral contraceptives, penicillins, phenothiazines, progesterone, sulfonamides, tamoxifen, and tolbutamide
  • Drugs and other substances that may increase AST levels by causing hepatocellular damage include acetaminophen, acetylsalicylic acid, allopurinol, amiodarone, anabolic steroids, anticonvulsants, asparaginase, azithromycin, bromocriptine, captopril, cephalosporins, chloramphenicol, clindamycin, clofibrate, danazol, enflurane, ethambutol, ethionamide, fenofibrate, fluconazole, fluoroquinolones, foscarnet, gentamicin, indomethacin, interferon, interleukin-2, levamisole, levodopa, lincomycin, low-molecular-weight heparin, methyldopa, monoamine oxidase inhibitors, naproxen, nifedipine, nitrofurans, oral contraceptives, probenecid, procainamide, quinine, ranitidine, retinol, ritodrine, sulfonylureas, tetracyclines, tobramycin, and verapamil
  • Drugs and other substances that may decrease AST levels include allopurinol, cyclosporine, interferon alpha, naltrexone, progesterone, trifluoperazine, and ursodiol
  • Hemolysis falsely increases AST values.
  • Hemodialysis falsely decreases AST values.

Nursing Implications Procedure

Related Studies

  • Related tests include acetaminophen, ALT, albumin, ALP, ammonia, AMA/ASMA, α1-antitrypsin/phenotyping, bilirubin and fractions, biopsy liver, cholangiography percutaneous transhepatic, cholangiography post-op, CT biliary tract and liver, ERCP, ethanol, ferritin, GGT, hepatitis antigens and antibodies, hepatobiliary scan, iron/total iron-binding capacity, liver and spleen scan, protein and fractions, PT/INR, US abdomen, and US liver.
  • See the Hepatobiliary System table online at DavisPlus for related tests by body system.


  • Positively identify the patient using at least two person-specific identifiers before services, treatments, or procedures are performed.
  • Patient Teaching: Inform the patient this test can assist in assessing liver function.
  • Obtain a history of the patient’s health concerns, symptoms, surgical procedures, and results of previously performed laboratory and diagnostic studies. Include a list of known allergens, especially allergies or sensitivities to latex.
  • Obtain a list of the patient’s current medications, including over-the-counter medications and dietary supplements (see Effects of Dietary Supplements online at DavisPlus).
  • Review the procedure with the patient. Inform the patient that specimen collection takes approximately 5 to 10 min. Address concerns about pain, and explain to the patient that there may be some discomfort during the venipuncture.
  • Sensitivity to social and cultural issues, as well as concern for modesty, is important in providing psychological support before, during, and after the procedure.
  • Note that there are no food, fluid, or medication restrictions unless by medical direction.


Potential Complications:

  • Avoid the use of equipment containing latex if the patient has a history of allergic reaction to latex.
  • Instruct the patient to cooperate fully and to follow directions. Direct the patient to breathe normally and to avoid unnecessary movement.
  • Observe standard precautions, and follow the general guidelines in Patient Preparation and Specimen Collection online at DavisPlus. Positively identify the patient, and label the appropriate specimen container with the corresponding patient demographics, initials of the person collecting the specimen, date, and time of collection. Perform a venipuncture.
  • Remove the needle and apply direct pressure with dry gauze to stop bleeding. Observe/assess venipuncture site for bleeding or hematoma formation and secure gauze with adhesive bandage.
  • Promptly transport the specimen to the laboratory for processing and analysis.

Post Test

  • Inform the patient that a report of the results will be made available to the requesting health-care provider (HCP), who will discuss the results with the patient.
  • Nutritional Considerations: Increased AST levels may be associated with liver disease. Dietary recommendations may be indicated and will vary depending on the condition and its severity. Currently, there are no specific medications that can be given to cure hepatitis, but elimination of alcohol ingestion and a diet optimized for convalescence are commonly included in the treatment plan. A high-calorie, high-protein, moderate-fat diet with a high fluid intake is often recommended for patients with hepatitis. Treatment of cirrhosis is different; a low-protein diet may be in order if the patient’s liver can no longer process the end products of protein metabolism. A diet of soft foods may be required if esophageal varices have developed. Ammonia levels may be used to determine whether protein should be added to or reduced from the diet. Patients should be encouraged to eat simple carbohydrates and emulsified fats (as in homogenized milk or eggs) rather than complex carbohydrates (e.g., starch, fiber, and glycogen [animal carbohydrates]) and complex fats, which require additional bile to emulsify them so that they can be used. The patient with cirrhosis should be observed carefully for the development of ascites, in which case fluid and electrolyte balance requires strict attention.
  • Recognize anxiety related to test results, and be supportive of fear of shortened life expectancy. Discuss the implications of abnormal test results on the patient’s lifestyle. Provide teaching and information regarding the clinical implications of the test results, as appropriate. Educate the patient regarding access to counseling services.
  • Instruct the patient to immediately report chest pain and changes in breathing pattern to the HCP.
  • Reinforce information given by the patient’s HCP regarding further testing, treatment, or referral to another HCP. Answer any questions or address any concerns voiced by the patient or family.
  • Depending on the results of this procedure, additional testing may be performed to evaluate or monitor progression of the disease process and determine the need for a change in therapy. Evaluate test results in relation to the patient’s symptoms and other tests performed.
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