Liver Function Tests

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Also known as: LFTs, Liver panel, Hepatic function tests

At a Glance

Why Get Tested?

To screen for and monitor liver disease

When to Get Tested?

When you have symptoms of a liver disorder such as jaundice or have been exposed to substances that can cause liver damage such as a paracetamol overdose

Sample Required?

A blood sample taken from a vein in your arm

Test Preparation Needed?

None

The Test Sample

What is being tested?

The liver is a large organ located in the upper right-hand part of the abdomen behind the lower ribs. It takes up drugs and toxic substances from the blood and renders them harmless. It produces proteins, including enzymes and blood clotting factors, helps maintain hormone balance and stores vitamins. The liver produces bile, a fluid that is transported through ducts to the gallbladder to be stored and then to the small intestine to help digest fats.

Liver disease is detected, evaluated and monitored by combinations of up to five tests measured 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
  • 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, conjugated bilirubin, measures the form made only in the liver and is often requested with total bilirubin in infants with jaundice
  • Alkaline phosphatase (ALP) – an enzyme related to the bile ducts; often increased when they are blocked, either inside or outside the liver
  • Albumin – measures the main protein made by the liver and tells how well the liver is making this protein
  • Total protein - measures albumin and all other proteins in blood, including antibodies made to help fight off infections

Other tests that can help to assess liver function include gamma-glutamyl transferase (GGT), 5’-nucleotidase (5’-NT) and prothrombin time (PT), 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.

NOTE: If undergoing medical tests makes you or someone you care for anxious, embarrassed, or even difficult to manage, you might consider reading one or more of the following articles: Coping with Test Pain, Discomfort, and Anxiety, Tips on Blood Testing, Tips to Help Children through Their Medical Tests, and Tips to Help the Elderly through Their Medical Tests.

Another article, Follow That Sample, provides a glimpse at the collection and processing of a blood sample and throat culture.

Is any test preparation needed to ensure the quality of the sample?

No test preparation is needed.

The Test

Common Questions

Ask a Laboratory Scientist

Article Sources

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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.