Testing levels of various substances in the blood can provide information about how the liver is functioning and whether it is currently sustaining damage. These blood tests are collectively referred to as liver function tests, or LFTs. LFTs can help detect liver disease progression and may provide information leading to a diagnosis of cirrhosis or liver failure. The National Institute of Diabetes and Digestive and Kidney Diseases reports cirrhosis of the liver–the end stage of any progressive liver disease–causes approximately 27,000 deaths annually in the U.S.
Albumin
Albumin is a protein made by the liver. It is the most plentiful protein in the blood. Testing the blood albumin is one way of measuring the liver’s capacity to produce proteins normally.
Alanine Transaminase
Alanine transaminase, or ALT, is an enzyme–a special type of protein that helps conduct chemical reactions. ALT is highly concentrated in liver cells. A high blood level of ALT may indicate active liver damage. However, ALT is not an absolute indicator of the presence or absence of liver disease. For example, the CDC reports people with chronic hepatitis C commonly have fluctuations in liver enzyme levels, which may occasionally be in the normal range despite ongoing liver disease. Other names for this enzyme include alanine aminotransferase and glutamate pyruvate transaminase or GPT.
Aspartate Transaminase
Aspartate transaminase, or AST, is another enzyme present in high concentrations in the liver. It is also present in muscle cells and the heart. A high blood AST may indicate active liver damage. Other names of this enzyme include aspartate aminotransferase and glutamate oxaloacetate transaminase, or GOT.
Bilirubin
Bilirubin is a breakdown product of red blood cells. The liver processes bilirubin for excretion in the bile. Hence, the bilirubin level in the blood is an indicator of the liver’s metabolic capacity. An abnormally elevated bilirubin is often an indicator of a problem in the liver or gallbladder. Bilirubin is an intensely yellow chemical. When this substance builds up in the blood, it causes jaundice–yellowing of the skin and eyes.
Fibrinogen
Fibrinogen is a clotting protein made by the liver. The fibrinogen level drops if the liver is failing and cannot keep up with the body’s protein production demands. A significantly decreased fibrinogen level may cause easy bleeding or bruising.
Gamma-Glutamyltransferase
Gamma-glutamyltransferase, or GGT, is found in most cells of the body, including liver cells. Liver cell damage causes GGT to leak into the bloodstream, causing an abnormal elevation. GGT is markedly elevated if bile flow from the liver to the gallbladder is blocked. An alternative name for this enzyme is gamma-glutamyl transpeptidase.
Lactate Dehydrogenase
Lactate dehydrogenase, or LDH, is an enzyme found in high concentrations in liver, heart and muscle cells. An elevated LDH may indicate ongoing liver damage. Other names of this enzyme include lactic dehydrogenase and lactic acid dehydrogenase.
Prothrombin Time
Prothrombin time, or PT, tests the blood’s clotting ability. This is relevant to the liver because the various proteins required for blood clotting are made by the liver. An abnormally prolonged PT test may indicate the liver is damaged to the point of being unable to produce sufficient clotting proteins.
Total Protein
The total protein blood test measures all types of proteins circulating in the blood–albumin, clotting factors and others. The liver makes most of the circulating blood proteins. Thus, the total protein test is a gross measure of the liver’s protein-making capacity. With serious liver disease, the liver is unable to produce sufficient blood proteins.
Learn more blood test results:
- MPV Blood Test: What Does High or Low Mean
- MCH Blood Test: Low, High, What does it Mean
- MCHC Blood Test: Low, High, What does it Mean
- RDW Blood Test High: What does it Mean
About this Author
Tina Andrews has been a medical writer and editor since 2000. She has published in “Cancer,” “Ethnicity & Disease,” and “Liver Health Today,” and was formerly a medical officer with the Centers for Disease Control and Prevention. Andrews holds a Doctor of Medicine degree and a Bachelor of Arts in chemistry.
