ALT and AST are two enzymes found in the liver that can indicate normal or abnormal liver function.

The normal range for ALT in the blood is 10 to 40 international units per liter (IU/L).

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

The normal range of AST in the blood is 10 to 34 IU/L.

The normal range depends on many things, including your age and gender. Normal value ranges may also vary slightly among different laboratories. Talk to your doctor about the meaning of your specific test results.

What Abnormal Results Mean

Increased levels of ALT or AST often means that liver disease is present. Liver disease is even more likely when levels of other liver blood tests are also increased.

An increase in ALT or AST levels may be due to:

• Cirrhosis (scarring of the liver)
• Death of liver tissue (liver necrosis)
• Hepatitis
• Hemochromatosis
• Lack of blood flow to the liver (liver ischemia)
• Liver tumor or cancer
• Medications that are toxic to the liver
• Mononucleosis (“mono”)
• Pancreatitis (swollen and inflamed pancreas)