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Liver Blood Tests (cont.)

Normal Levels of AST and ALT

Normal levels of AST and ALT may slightly vary depending on the individual laboratory's reference values. Typically the range for normal AST is reported between 10 to 40 units per liter and ALT between 7 to 56 units per liter.

Mild elevations are generally considered to be 2-3 times higher than the normal range. In some conditions, these enzymes can be severely elevated, in the 1000s range.

Elevated Levels of AST and ALT

Elevated levels of liver enzymes in general signify some form of liver (or hepatic) damage or injury. These levels may be elevated acutely (short term) indicating sudden injury to the liver, or they may be elevated chronically (long term) suggesting ongoing liver injury.

In addition to the duration, the level of abnormal elevation of the aminotransferases is also significant. In some conditions the elevation could be mild, consistent with a mild injury or inflammation of the liver. They can also be severely elevated, possibly up to 10 to 20 times the normal values, suggesting more significant damage to the liver.

Diseases That Cause Abnormal Aminotransferase Levels

The most common diseases causing abnormally elevated ALT and AST are:

  • Acute viral hepatitis, such as hepatitis A or B
  • Chronic viral hepatitis, such hepatitis B or C
  • Cirrhosis of the liver (scarring of the liver due to long standing inflammation of the liver)
  • Liver damage from alcohol abuse or alcoholic fatty liver
  • Hemochromatosis (a genetic condition causing long standing liver damage due to iron build up in the liver)
  • Diminished blood flow to the liver (from shock or heart failure)
Medically Reviewed by a Doctor on 8/19/2015

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Liver Blood Tests - Causes

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