What are some common liver tests?

A series of blood tests can often find out if the liver is inflamed, injured, or working normally. These tests can also tell the difference between acute and chronic liver disorders. And they can tell the difference between hepatitis (infection or inflammation of the liver) and cholestasis (problems with the flow of bile). 

The most common blood tests are below.

Liver function tests

• Serum bilirubin test. This test measures the levels of bilirubin in the blood. Bilirubin is made by the liver and is excreted in the bile. High levels of bilirubin may mean there is a blockage of bile flow. Or it could mean a problem with how the liver processes bile.

• Serum albumin test. This test is used to measure the level of albumin. Albumin is a protein in the blood. The test may help in the diagnosis of liver disease. Low levels of albumin may mean the liver is not working normally. 

• International normalized ratio (INR). This used to be known as the prothrombin time (PT) test. This test measures how long it takes for blood to clot. Blood clotting needs vitamin K and a protein that is made by the liver. Blood that takes a long time to clot may mean liver disease. Or it may mean low levels of certain clotting factors.

Liver enzyme tests

• Serum alkaline phosphatase test. This test is used to measure the blood level of an enzyme called alkaline phosphatase. This enzyme is found in many tissues. The highest amounts are in the liver, biliary tract, and bones. This test may be done to check liver function. And it may be done to find liver lesions that may cause bile blockage, such as tumors or abscesses.

• Alanine transaminase (ALT) test. This test measures the level of alanine aminotransferase. This is an enzyme found mostly in the liver. It is released into the bloodstream after acute liver cell damage. This test may be done to check liver function. Or it may be done to check on the treatment of acute liver disease, such as hepatitis.

• Aspartate transaminase (AST) test. This test measures the level of aspartate transaminase. This is an enzyme that is found in the liver, kidneys, pancreas, heart, skeletal muscle, and red blood cells. This enzyme is released into the bloodstream after acute liver cell damage.

• Gamma-glutamyl transpeptidase (GGT) test. This test measures the level of gamma-glutamyl transpeptidase. This is an enzyme that is made in the liver, pancreas, and biliary tract. This test is often done to check liver function, to give information about liver diseases, and to see if a person has had alcohol.

• Lactic dehydrogenase test. This test can find tissue damage and may help in the diagnosis of liver disease. Lactic dehydrogenase is a type of protein. It is also called an isoenzyme. It is involved in the body's metabolic process. But this is a very nonspecific liver test. It is rarely used for liver disease assessment.

• 5'-nucleotidase test. This test measures the levels of 5'-nucleotidase. This is an enzyme made only in the liver. The 5'-nucleotidase level is high in people with liver diseases, especially diseases that cause problems with the flow of bile (cholestasis).

Other diagnostic tests

Other diagnostic liver tests may be done if a specific disease is suspected. These tests include:

• Alpha-fetoprotein (AFP) test. Alpha-fetoprotein is a blood protein made by fetal tissue and by tumors. This test may be done to predict the risk for primary liver cancer (hepatocellular carcinoma). It is also done to see how well therapy is working to treat certain cancers, such as hepatoma (a type of liver cancer).

• Antimitochondrial antibodies (AMAs). These antibodies in the blood can mean primary biliary cirrhosis, chronic active hepatitis, or other autoimmune disorders. Many other antibodies are also suggestive of liver disease and can be found in blood.

• Serum alpha-1 antitrypsin test (A1AT). This test measures the levels of alpha-1 antitrypsin in the blood. This test is done to help find a rare form of emphysema in adults. And it is done to find a rare form of liver disease (cirrhosis) in children and adults.

• Viral hepatitis tests. These check if you have or had hepatitis A, B, C, D, or E. In the U.S., hepatitis D and E are uncommon.

• Certain blood tests can suggest metabolic liver disease in people with obesity, diabetes, high blood pressure, heart disease, and high cholesterol.