Liver function tests check the levels of certain enzymes and proteins in your blood. Levels that are higher or lower than normal can indicate liver problems. Some common liver function tests include:
Alanine transaminase (ALT). ALT is an enzyme found in the liver that helps your body metabolize protein. When the liver is damaged, ALT is released into the bloodstream and levels increase.
Normal value of ALT is 7 to 55 units per liter (U/L).
Aspartate transaminase (AST). AST is an enzyme that helps metabolize alanine, an amino acid. Like ALT, AST is normally present in blood at low levels. An increase in AST levels may indicate liver damage or disease or muscle damage.
Normal value of AST is 8 to 48 U/L.
Alkaline phosphatase (ALP). ALP is an enzyme in the liver, bile ducts and bone. Higher-than-normal levels of ALP may indicate liver damage or disease, such as a blocked bile duct, or certain bone diseases.
Normal value of ALP is 45 to 115 U/L.
Albumin and total protein. Albumin is one of several proteins made in the liver. Your body needs these proteins to fight infections and to perform other functions. Lower-than-normal levels of albumin and total protein might indicate liver damage or disease.
Normal value of Albumin is 3.5 to 5.0 grams per deciliter (g/dL).
Normal value of total protein is 6.3 to 7.9 g/dL.
Bilirubin. Bilirubin is a substance produced during the normal breakdown of red blood cells. Bilirubin passes through the liver and is excreted in stool. Elevated levels of bilirubin (jaundice) might indicate liver damage or disease or certain types of anemia.
Normal value of Bilirubin is 0.1 to 1.2 milligrams per deciliter (mg/dL).
Gamma-glutamyltransferase (GGT). GGT is an enzyme in the blood. Higher-than-normal levels may indicate liver or bile duct damage.
Normal value of GGT is 9 to 48 U/L.
L-lactate dehydrogenase (LD). LD is an enzyme found in the liver. Elevated levels may indicate liver damage but can be elevated in many other disorders.
Normal value of LD is 122 to 222 U/L.
Prothrombin time (PT). PT is the time it takes your blood to clot. Increased PT may indicate liver damage but can also be elevated if you’re taking certain blood-thinning drugs, such as warfarin.
Normal value of PT is 9.5 to 13.8 seconds.
This table shows examples of some combinations of results that may be seen in certain types of liver conditions or diseases.
|Type of liver condition or disease||Bilirubin||ALT and AST||ALP||Albumin||PT|
|Acute liver damage (due, for example, to infection, toxins or drugs, etc.)||Normal or increased usually after ALT and AST are already increased||Usually greatly increased (> 10 times); ALT is usually higher than AST||Normal or only moderately increased||Normal||Usually normal|
|Chronic forms of various liver disorders||Normal or increased||Mildly or moderately increased; ALT is persistently increased||Normal to slightly increased||Normal||Normal|
|Alcoholic Hepatitis||Normal or increased||AST is moderately increased, usually at least twice the level of ALT||Normal or moderately increased||Normal||Normal|
|Cirrhosis||May be increased but this usually occurs later in the disease||AST is usually higher than ALT but levels are usually lower than in alcoholic disease||Normal or increased||Normal or decreased||Usually prolonged|
|Bile duct obstruction, cholestasis||Normal or increased; increased in complete obstruction||Normal to moderately increased||Increased; often greater than 4 times what is normal||Usually normal but if the disease is chronic, levels may decrease||Usually normal|
|Cancer that has spread to the liver (metastasized)||Usually normal||Normal or slightly increased||Usually greatly increased||Normal||Normal|
|Cancer originating in the liver (hepatocellular carcinoma, HCC)||May be increased, especially if the disease has progressed||AST higher than ALT but levels lower than that seen in alcoholic disease||Normal or increased||Normal or decreased||Usually prolonged|
|Autoimmune||Normal or increased||Moderately increased; ALT usually higher than AST||Normal or slightly increased||Usually decreased||Normal|