What are liver function tests?

Liver function tests (LFTs) are common blood tests that check how well your liver is working. They measure different proteins, enzymes and other substances in your blood.

These tests help:

• find liver disease and liver problems
• check how severe any problems are
• track how well treatment is working

Your liver is a large organ in your abdomen. It helps your body by filtering harmful substances and breaking down medicines and alcohol. It also supports digestion, makes bile and produces important proteins and enzymes.

Liver function tests are also called hepatic function tests.

Different liver function tests

There are several liver function tests, including:

• alanine aminotransferase (ALT) — an enzyme that shows liver cell health
• albumin — a protein made by the liver that helps regulate fluids
• alkaline phosphatase (ALP) — an enzyme linked to bile flow and bone health, as well as made by the placenta during pregnancy
• aspartate aminotransferase (AST) — an enzyme that can indicate liver damage
• bilirubin — a substance that reflects bile production and excretion
• gamma glutamyl transferase (GGT) — an enzyme that can indicate liver stress
• total protein — the total amount of proteins in the blood, including albumin and globulins

What are proteins and enzymes?

Proteins are important building blocks in your body. Some proteins, such as albumin and globulins, help move nutrients, fight infections and balance fluids.

Enzymes are special proteins that speed up chemical reactions in your body. Liver enzymes, such as ALT and AST help break down substances and can show if your liver is damaged.

When are liver function tests used?

Your doctor may refer you for liver function tests to check for liver problems and monitor your liver health, especially if you:

• have or may have a liver condition or liver disease
• have or may have cirrhosis of the liver
• have or may have a hepatitis virus infection
• have signs of a biliary obstruction — a blockage in the bile ducts that stops bile from draining properly into your gut
• drink a lot of alcohol
• have a family history of liver disease
• take medicines that can affect your liver function

Your doctor might refer you for LFTs if you have symptoms such as:

• jaundice (yellowing of the skin or eyes)
• dark urine (wee) or light-coloured faeces (poo)
• nausea and vomiting
• abdominal (tummy) pain or swelling
• itching

Where can I get a liver function test?

You usually need to go to a pathology collection centre with a referral from your doctor. Your doctor will recommend one near you.

Sometimes, your doctor will collect blood for testing in their clinic. Blood tests are also routinely done in hospitals.

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How do I prepare for a liver function test?

There is no special preparation needed for a liver function test.

However, if you are having other blood tests done at the same time, you may need to prepare. Check with your doctor or the pathology collection centre if there is anything you need to do before your blood test.

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What happens during a liver function test?

A liver function test is usually done at a pathology collection centre. A health professional will take a sample of blood, usually from a vein in your arm. The blood will then be sent to a laboratory for testing.

What do my liver function results mean?

Each liver function test gives different information about different aspects of your liver function and overall health.

The results do not diagnose a specific condition, but they can show signs of liver disease or damage.

If your test results are abnormal, your doctor may suggest further tests, such as:

• an ultrasound to check the liver's shape and size
• a CT scan or MRI scan for detailed pictures of your liver
• more blood tests to find out what's causing the problem

Some LFT results can also be affected by conditions elsewhere in the body. It's important to talk to your doctor about your results so they can explain what they mean for you.

Watch this video by Pathology Tests Explained to learn more about liver function test results.

Resources and support

Pathology Tests Explained has more information about liver function tests, including:

• Alanine aminotransferase (ALT)
• Albumin
• Alkaline phosphatase (ALP)
• Aspartate aminotransferase (AST)
• Bilirubin
• Gamma glutamyl transferase (GGT)

Read our 'Guide to blood testing' to learn more about blood tests, including:

• what to consider before having the test
• what happens during a blood test
• how accurate results are
• blood test costs

You can also call the healthdirect helpline on 1800 022 222 (known as NURSE-ON-CALL in Victoria). A registered nurse is available 24 hours a day, 7 days a week.