ALT, AST, and Bilirubin

ALT (alanine aminotransferase) is an enzyme primarily found in liver cells. It participates in amino acid metabolism and is released into the blood when liver cells are damaged. Elevated ALT levels most often indicate liver inflammation or injury caused by hepatitis, toxins, alcohol, medications, or other diseases.

AST (aspartate aminotransferase) is an enzyme present in the liver, heart, muscles, and other organs. Elevated AST can be related not only to liver damage but also to heart diseases (e.g., myocardial infarction), muscle injuries, and other conditions. The AST to ALT ratio helps determine the nature of liver damage.

Bilirubin is a breakdown product of hemoglobin from red blood cells. It exists in two forms: direct (conjugated) and indirect (unconjugated). Elevated bilirubin leads to jaundice of the skin and mucous membranes and often indicates liver dysfunction, bile duct obstruction, or increased red blood cell destruction (hemolysis).

Reasons for ALT, AST, and bilirubin testing:

• Assessment of liver function and detection of liver damage.
• Diagnosis of hepatitis, cirrhosis, fatty liver disease, and other liver conditions.
• Determining causes of jaundice.
• Monitoring the effectiveness of liver disease treatment.

Test procedure:

• Blood is drawn from a vein fasting.
• Avoid alcohol, fatty foods, and intense physical activity before the test.

Important notes:

• ALT and AST levels together with bilirubin provide a comprehensive view of liver status.
• The AST to ALT ratio aids in differentiating types of liver injury.
• Additional tests (liver ultrasound, biopsy) may be needed for accurate diagnosis.