There are a number of blood tests that may be used to diagnose hepatitis. A liver panel contains tests for a number of enzymes produced by the liver. Persistent elevation of the liver enzymes ALT and GGT can indicate damage to liver cells, decreasing the ability of the liver to perform its many functions. There are tests for antibodies against each type of virus that causes hepatitis. Elevated bilirubin levels appear most obviously as yellowing of the skin and whites of the eyes, indicating breakdown of liver cells and an inability to process bile.
A liver biopsy, in which a needle is inserted into the liver to withdraw a small amount of cells that are examined under a microscope by a pathologist, is the most definitive way to diagnose the disease. Since this is an invasive procedure requiring skill on the part of the physician performing the biopsy, it is used primarily when other tests are inconclusive, or to determine how much damage to the liver has occurred.
Screening donated blood for the presence of hepatitis virus infection and other communicable diseases has greatly reduced the transmission of infections through this route.