AST (aspartate aminotransferase) is an enzyme found in high amounts in heart muscle and liver and skeletal muscle cells. It is also found in lesser amounts in other tissues.

This article discusses the test to measure the amount of AST in the blood.

Blood is typically drawn from a vein, usually from the inside of the elbow or the back of the hand. The site is cleaned with germ-killing medicine (antiseptic). The health care provider wraps an elastic band around the upper arm to apply pressure to the area and make the vein swell with blood.

Next, the health care provider gently inserts a needle into the vein. The blood collects into an airtight vial or tube attached to the needle. The elastic band is removed from your arm.

Once the blood has been collected, the needle is removed, and the puncture site is covered to stop any bleeding.

In infants or young children, a sharp tool called a lancet may be used to puncture the skin and make it bleed. The blood collects into a small glass tube called a pipette, or onto a slide or test strip. A bandage may be placed over the area if there is any bleeding.

When the needle is inserted to draw blood, some people feel moderate pain, while others feel only a prick or stinging sensation. Afterward, there may be some throbbing.

This test is mainly done along with other tests (such as ALT, ALP, and bilirubin) to diagnose and monitor liver disease.

The normal range is 10 to 34 IU/L.

Note: IU/L = international units per liter

Diseases that affect liver cells increase the levels of AST. However, increased levels of AST alone do not specifically indicate liver disease.

An increase in AST levels may indicate:

• Acute hemolytic anemia
• Acute pancreatitis
• Acute renal failure
• Cirrhosis
• Heart attack
• Hepatitis
• Hereditary hemochromatosis
• Infectious mononucleosis
• Lack of blood flow to the liver (liver ischemia)
• Liver necrosis
• Liver tumor
• Multiple trauma
• Primary muscle disease
• Progressive muscular dystrophy
• Recent cardiac catheterization or angioplasty
• Recent convulsion
• Recent surgery
• Severe deep burn
• Skeletal muscle trauma
• Use of drugs that are poisonous to the liver

Other risks associated with having blood drawn are slight but may include:

• Excessive bleeding
• Fainting or feeling light-headed
• Hematoma (blood accumulating under the skin)
• Infection (a slight risk any time the skin is broken)

AST levels may rise during pregnancy and after exercise.

Berk PD, Korenblat KM. Approach to the patient with jaundice or abnormal liver test results. In: Goldman L, Ausiello D, eds. Cecil Medicine. 23rd ed. Philadelphia, Pa: Saunders Elsevier; 2007:chap 150.