Liver function tests are blood tests used to help diagnose and monitor liver disease or damage. These tests measure the levels of certain enzymes and proteins in the blood.

Some of these tests measure how well the liver performs its normal functions of producing protein and removing bilirubin, a blood waste product. Other liver function tests measure enzymes that liver cells release in response to injury or disease.


Abnormal liver function test results do not always indicate liver disease. Your doctor will explain your results and what they mean.


Why it's done

Liver function tests can be used to:

  • screening for liver infections, such as hepatitis
  • Monitor the progression of diseases such as viral or alcoholic hepatitis and determine the effectiveness of treatment
  • To measure the severity of the disease, especially scarring of the liver (cirrhosis)
  • Monitor possible side effects of medications

Liver function tests check the levels of certain enzymes and proteins in the blood. Higher or lower than normal levels may indicate a problem with the liver. Some common liver function tests include:

  • Alanine aminotransferase (ALT). ALT is an enzyme found in the liver that helps convert protein into energy for liver cells. When the liver is damaged, ALT is released into the blood and levels rise.
  • Aspartate aminotransferase (AST). AST is an enzyme that helps metabolize amino acids. Like ALT, AST is usually found in low levels in the blood. Elevated AST levels may indicate liver-damaging disease or muscle damage.
  • Alkaline phosphatase (ALP). ALP is an enzyme found in the liver and bones that is important for breaking down proteins. Higher-than-normal levels of ALP may indicate liver damage or disease, such as blockage in the bile ducts or certain bone disorders.
  • albumin and total protein. Albumin is one of several proteins produced in the liver. Your body needs these proteins to fight infection and perform other functions. Lower-than-normal levels of albumin and total protein may indicate liver damage or disease.
  • bilirubin. Bilirubin is a substance produced during the normal breakdown of red blood cells. Bilirubin passes through the liver and is excreted in the feces. Elevated bilirubin levels (jaundice) may indicate liver damage or disease or certain types of anemia.
  • Gamma-glutamyltransferase (GGT). GGT is an enzyme in the blood. Higher than normal levels may indicate damage to the liver or bile ducts.
  • L-lactate dehydrogenase (LD). LD is an enzyme found in the liver. Elevated levels may indicate liver damage, but they can also be elevated in many other conditions.
  • Prothrombin time (PT). PT is the time it takes for blood to clot. An elevated PT can indicate liver damage, but it can also be elevated if you are taking certain blood-thinning medications, such as warfarin.