Liver function tests

This page tells you about liver function tests. There is information about

• What liver function tests are
• What the liver does
• Why you may have liver function tests
• Having the test

• What LFTs can show
• Questions for your doctor
• Where to find information about liver cancer

A liver function test is a common blood test. Doctors ask you to have this test to find out how well your liver is working. Sometimes it is purely a routine test. At other times the doctor uses it to find out why you have particular symptoms. A liver function test is actually a series of tests to look for different things within a sample of your blood. This is why they are usually called liver function tests, or LFTs for short.

The liver is the chemical factory of the body. It performs many important jobs including

• Storing some digested foods (nutrients)
• Converting fat to energy when the body needs it
• Producing bile
• Making blood proteins
• Helping the blood to clot
• Making other chemicals the body needs
• Breaking down harmful substances

A blood test can show problems with these processes, and help the doctor to find out what could be causing the problems.

You may have liver function tests for the following reasons.

• As part of a general health check when you are first diagnosed with cancer or other illnesses
• To help diagnose the cause of symptoms, such yellowing of the skin and whites of the eyes (jaundice)
• Before and after treatment, to check how well your liver is working
• To check for secondary cancer in the liver, along with other tests such as an ultrasound scan, CT scan or liver biopsy

You can have LFTs done at the GP surgery or hospital. Occasionally you may be asked not to eat anything for a few hours before the test. If you are taking any medicines, you should take them as normal unless you are told otherwise. You may have blood taken for other tests at the same time. For example, you might have a full blood count to check for anaemia.

The results should be ready either on the same day or within a few days.  How soon you get them depends on how urgent the test is.

Liver function tests can show many things. They can give the doctor an idea of which disease may be causing changes in the liver.  But they aren’t enough in themselves to make a diagnosis. They are one of a series of tests done to diagnose disease. If you are already diagnosed with a condition, LFTs can be helpful in monitoring your disease or treatment. The doctor can look for a rise or fall in the levels of substances tested, which may indicate damage or improvement to your liver.

Below are some of the substances that the doctor may want to look at in your blood. These include enzymes and proteins made by the liver.

• Alanine aminotransferase (ALT) 
• Aspartate aminotransferase (AST) 

These are both enzymes that help to process proteins. ALT and AST levels may be raised if your liver is inflamed or injured.

• Alkaline Phosphatase (ALP) 
• Gamma-Glutamyl transferase (Gamma GT) 

These are also both enzymes. ALP and GT may be raised when there is a blockage in your liver or bile duct, or if you drink a lot of alcohol.

• Bilirubin 

Bilirubin is a chemical in bile. High levels in the blood cause jaundice. Bilirubin may be raised when there is a problem with your liver or gallbladder.

• Albumin

This is a protein that may be at a low level with some types of cancer. Albumen can also be low if you have not  been eating properly and are malnourished.

You may also have blood tests called clotting studies. These show if your blood is clotting normally to stop bleeding. Because the liver makes the proteins that are needed for clotting, these tests can help to show up liver problems.

• Why do I need this test?
• What are you looking for?
• When will I get the results?
• If the result is abnormal, which part of the test is abnormal, and what does it mean?
• Will I need any more tests?
• Will my treatment change?

There is information about liver cancer in the primary liver cancer section of CancerHelp UK. If you have, or are worried about, cancer that may have spread to your liver, you should look at the section about the cancer that you were originally diagnosed with. There is a list of these sections on different types of cancer in CancerHelp UK.