Liver function tests
What is a liver function test? What does it involve and are there any specific questions that I can ask the doctor?
Liver function tests are a group of commonly used blood tests. Doctors do them to find out how well your liver is working. Sometimes this is purely routine. At other times the doctor use them to find out why you have particular symptoms. These tests can be called 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 up problems and help the doctor to find out what could be causing them.
You may have liver function tests
- As part of a general health check when you are first diagnosed with cancer or other illnesses
- To help find out why you have particular symptoms, such yellowing of the skin and whites of the eyes (jaundice)
- To check how well your liver is working before and after treatment
- 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. Your doctor may ask you not to eat anything for a few hours before the test. If you are taking any medicines, take them as normal unless you are told otherwise. You may have blood taken for other tests at the same time.
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. You need a series of tests to diagnose a disease. If you are already diagnosed, LFTs can help to monitor your disease or treatment. The doctor can look for a rise or fall in the tests, which may mean either damage or improvement to your liver.
LFTs look for levels of enzymes and proteins made by the liver. We've listed some of these below.
- Alanine aminotransferase (ALT)
- Aspartate aminotransferase (AST)
are both enzymes that help to process proteins. They may be raised if your liver is inflamed or injured.
- Alkaline Phosphatase (ALP)
- Gamma-Glutamyl transferase (Gamma GT)
are also both enzymes. They may be raised if you have a blockage in your liver or bile duct, or if you drink a lot of alcohol.
is a chemical in bile. High levels in the blood cause jaundice. Bilirubin may be raised if you have a problem with your liver or gallbladder.
is a protein that may be low in some types of cancer. It can also be low if you haven't 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 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 our primary liver cancer section.
If you have another type of cancer that may have spread to your liver (secondary liver cancer), you should look at the section for the cancer that you were originally diagnosed with (the primary cancer). This is because cancer cells in your liver will be of the primary cancer type and will respond to treatments for that cancer. This link will take you to a list of sections on different types of cancer.
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