The liver is the organ that removes all toxic substances from your blood. When you take medicines, it is the liver that helps you detoxify the substances. The liver is unique because it can regenerate itself. Even when a part of liver is damaged, it can regenerate itself from healthy cells. Alcohol and abuse of drugs puts a strain on the liver cells and can cause irreversible damage. Hepatitis primarily affects the liver cells. The liver also produces proteins, enzymes, store vitamins, produces blood clotting factors and helps maintain hormones. The liver also produces bile which helps in digesting fats. Liver function tests are used to understand the health of the liver and its optimal functioning.

Reference Values
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 litre and ALT between 7 to 56 units per litre. Mild elevations are generally considered to be 2-3 times higher than the normal range.

Interpretations
There may be damage to the liver when the values of AST and ALT are higher. It is observed that in hepatitis, ALT results are higher than AST. Your doctor may also order a Creatinine Kinase or a CK test or a troponin test. A creatine kinase test confirms damage to the muscles and elevated troponin levels means that there is damage to the heart.

Gamma-glutamyl transferase or the GGT test is more sensitive in detecting liver damage from drugs and alcohol. The GGT test is also used for detecting early rejection after liver transplantation.

Gall stones or problem with the gallbladder is usually signalled by elevated bilirubin levels. In newborn babies, raised bilirubin levels could means that there is a problem with the liver.