At a Glance
Why Get Tested?
To screen for, detect, evaluate and monitor for liver inflammation and damage.
When to Get Tested?
A blood sample drawn from a vein in your arm.
Test Preparation Needed?
The Test Sample
What is being tested?
Liver Function Tests (LFTs) is a group of tests that are performed together to detect, evaluate, and monitor liver disease or damage. The liver is one of the largest organs in the body and is located in the upper right-hand part of the abdomen and behind the lower ribs. The liver metabolises and detoxifies drugs and substances that are harmful to the body. It produces blood clotting factors, proteins, and enzymes, helps maintain hormone balances, and stores vitamins and minerals. Bile, a fluid produced by the liver, is transported through ducts directly to the small intestine to help digest fats or to the gallbladder to be stored and concentrated for later use.
A variety of diseases and infections can cause acute or chronic damage to the liver, causing inflammation, scarring, bile duct obstructions, clotting abnormalities, and liver dysfunction. Alcohol, drugs, some herbal supplements, and toxins can also pose a threat. A significant amount of liver damage may be present before symptoms such as jaundice, dark urine, light-colored stools, pruritus, nausea, fatigue, diarrhoea, and unexplained weight loss or gain emerge. Early detection is essential in order to minimize damage and preserve liver function.
LFTs measure enzymes, proteins, and substances that are produced or excreted by the liver and are affected by liver injury. Some are released by damaged liver cells and some reflect a decrease in the liver's ability to perform one or more of its functions. When performed together, these tests give the doctor a snapshot of the health of the liver, an indication of the potential severity of any liver injury, change in liver status over time, and a starting place for further diagnostic testing.
The panel usually consists of several tests that are run at the same time on a blood sample. These may include:
- Alanine aminotransferase (ALT) – an enzyme mainly found in the liver; the best test for detecting hepatitis
- Alkaline phosphatase (ALP) – an enzyme related to the bile ducts; often increased when they are blocked
- Aspartate aminotransferase (AST) – an enzyme found in the liver and a few other places, particularly the heart and other muscles in the body
- Total bilirubin – measures all the yellow bilirubin pigment in the blood. Another test, direct bilirubin, measures a form combined with another compound in the liver and is often requested with total bilirubin in infants with jaundice.
- Albumin – measures the main protein made by the liver and tells whether or not the liver is making an adequate amount of this protein
- Gamma-glutamyl transferase (GGT) - an enzyme found mainly in the liver and is a useful marker for detecting bile duct problems
- Total protein - measures albumin and all other proteins in blood, including antibodies made to help fight off infections
Other tests that can be used to assess liver function include a coagulation screen, together with bilirubin and urobilinogen in urine.
How is the sample collected for testing?
A blood sample is obtained by inserting a needle into a vein in the arm.
Is any test preparation needed to ensure the quality of the sample?
No test preparation is needed.
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NOTE: This article is based on research that utilizes the sources cited here as well as the collective experience of the Lab Tests Online Editorial Review Board. This article is periodically reviewed by the Editorial Board and may be updated as a result of the review. Any new sources cited will be added to the list and distinguished from the original sources used.