At a glance

Also known as

LFT

Why get tested?

To screen for, detect, evaluate and monitor for liver inflammation and damage.

When to get tested?

Periodically to evaluate liver function; whenever you are at risk for liver injury; when you have a liver disease; when you have symptoms such as jaundice.

Sample required?

A blood sample drawn from a vein in your arm.

Test preparation needed?

None

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.

The Test

How is it used?

Liver Function Tests (LFTs) may be used to screen a person for liver damage, especially someone who has a condition, or is taking a drug, that may affect the liver.

LFTs or one or more component tests may be used to help detect liver disease if a person has symptoms that indicate possible liver dysfunction or if a person is being monitored or treated for a known condition or liver disease. A bilirubin test, for instance, may be ordered to evaluate and monitor a jaundiced newborn.

Abnormal tests on a liver function tests panel may prompt a repeat analysis to see if the elevation or decrease persists and/or may indicate the need for additional testing to determine the cause of the liver dysfunction.

The group of tests may also be ordered to monitor liver function and the effectiveness of treatment in someone who has a liver disease.

When is it requested?

LFTs, or one or more components, may be ordered when someone is at risk for liver dysfunction. Some examples include:

  • people who have a history of known or possible exposure to hepatitis viruses
  • those who are heavy drinkers
  • individuals whose families have a history of liver disease
  • people who take drugs that might occasionally damage the liver

LFTs may be ordered when a person has signs and symptoms of liver disease. Some of these include:

  • Weakness, fatigue
  • Loss of appetite
  • Nausea, vomiting
  • Abdominal swelling and/or pain
  • Jaundice
  • Dark urine, light coloured stool
  • Itching (pruritus)

Usually no one single set of liver tests are used to make a diagnosis. Often, several LFTs will be ordered over a few days or weeks to determine if a pattern is present and to help determine the cause of the liver disorder.

When liver disease is detected, it may be monitored on a regular basis over time with the LFTs or with one or more of its components. LFTs may also be ordered regularly to monitor the effectiveness of treatment for the liver disorder.

What does the test result mean?

LFT results are not diagnostic of a specific condition; they indicate that there may be a problem with the liver. In a person who does not have symptoms or identifiable risk factors, abnormal liver test results may indicate a temporary liver injury or reflect something that is happening elsewhere in the body – such as in the skeletal muscles, pancreas, or heart. It may also indicate early liver disease and the need for further testing and/or periodic monitoring.

Results of LFTs are usually evaluated together. Several sets of results from tests performed over a few days or weeks are often assessed together to determine if a pattern is present. Each person will have a unique set of test results that will typically change over time. A doctor evaluates the combination of liver test results to gain clues about the underlying condition. Often, further testing is necessary to determine what is causing the liver damage and/or disease.

The table below shows examples of some combinations of results that may be seen in certain types of liver conditions or diseases.

Type of liver condition or disease

Bilirubin

ALT and AST

ALP and GGT

Albumin

PT

Acute liver damage (due, for example, to infection, toxins or drugs, etc.)

Normal or increased usually after ALT and AST are already increased

Usually greatly increased; ALT is usually higher than AST

Normal or only moderately increased

Normal

Usually normal

Chronic forms of various liver disorders

Normal or increased

Moderately increased

Normal to slightly increased

Normal

Normal

Alcoholic Hepatitis

Normal or increased

AST is usually higher than the level of ALT

Normal or moderately increased, GGT markedly increased

Normal

Normal

Cirrhosis

May be increased but this usually occurs later in the disease

AST is usually higher than ALT but levels are usually lower than in alcoholic disease

Normal or increased

Usually decreased

Usually prolonged

Bile duct obstruction, cholestasis

Normal or increased; increased in complete obstruction

Normal to moderately increased

Increased; often greater than 4 times what is normal

Usually normal but if the disease is chronic, levels may decrease

Usually normal

Cancer that has spread to the liver (metastasized)

Usually normal

Normal or slightly increased

Usually greatly increased

Normal

Normal

Cancer originating in the liver (hepatocellular carcinoma, HCC)

May be increased, especially if the disease has progressed

AST higher than ALT but levels lower than that seen in alcoholic disease

Normal or increased

Usually decreased

Usually prolonged

Autoimmune

Normal or increased

Moderately increased

Normal or slightly increased

Normal or decreased

Normal

If a person is taking drugs that may affect their liver, then abnormal test results may indicate a need to re-evaluate the dosage or choice of medication. When a person with liver disease is being monitored, then the doctor will evaluate the results of the liver panel together to determine if liver function in worsening or improving. For example, increasingly abnormal bilirubin, albumin, and/or PT may indicate a deterioration in liver function, while stable or improving results of these tests may indicate liver function preservation or improvement.

For individual tests:

Alanine aminotransferase (ALT)
A very high level of ALT is frequently seen with acute hepatitis. Moderate increases may be seen with chronic hepatitis. People with blocked bile ducts, cirrhosis, and liver cancer may have ALT concentrations that are only moderately elevated or close to normal.

Alkaline phosphatase (ALP)
ALP may be significantly increased with obstructed bile ducts, liver cancer, and also with bone disease.

Aspartate aminotransferase (AST)
A very high level of AST is frequently seen with acute hepatitis. AST may be normal to moderately increased with chronic hepatitis. In people with blocked bile ducts, cirrhosis, and liver cancer, AST concentrations may be moderately increased or close to normal. When liver damage is due to alcohol, AST often increases much more than ALT (this is a pattern seen with few other liver diseases). AST is also increased after heart attacks and with muscle injury.

Bilirubin
Bilirubin is increased in the blood when too much is being produced, less is being removed, due to bile duct obstructions, or to problems with bilirubin processing. It is not uncommon to see high bilirubin levels in newborns, typically 1 to 3 days old.

Albumin
Albumin is often normal in liver disease but may sometimes be low due to decreased production.

Total Protein
Total protein is typically normal with liver disease.

Gamma-glutamyl transferase (GGT)
A GGT test may be used to help determine the cause of an elevated ALP. Both ALP and GGT are elevated in bile duct and liver disease, but only ALP will be elevated in bone disease. Increased GGT levels are also seen with alcohol consumption and often in patients taking some drugs that are metabolized in the liver such as carbamazepine and phenobarbitone.

Prothrombin Time (PT)
A prolonged or increased PT can be seen with liver disease, vitamin K deficiency, and with coagulation factor deficiencies.

About Reference or “Normal” Ranges

Is there anything else I should know?

In order to diagnose a liver disease, a doctor will evaluate the liver panel test results, order follow-up tests such as hepatitis testing, and may order a liver biopsy and/or imaging scans to help confirm a diagnosis and determine the extent of liver damage.

Common Questions

Why does my doctor want to know all of the medications I am taking?

Many over-the-counter drugs and herbal or dietary supplements have the potential to affect the liver. Excessive paracetamol use and the combination of paracetamol and alcohol for instance can cause severe liver damage, as can exposure to toxins such as poisonous mushrooms.

Can I have liver disease if I feel fine?

Yes, early liver disease often causes no symptoms or mild nonspecific symptoms, such as fatigue and nausea.

Can I have abnormal test results and not have liver disease?

Yes, many temporary conditions, such as shock, burns, severe infections, muscle trauma, dehydrationpancreatitishaemolysis, and pregnancy can cause one or more of the liver function tests to be abnormal.

Why is my family history important?

Some liver conditions, such as haemochromatosis and Wilson's disease, may be inherited. Early detection of these conditions allows them to be treated and managed appropriately.

What tests may be done in follow up to abnormal liver function tests to help determine the cause of liver injury?

Depending on the results of the liver panel and other factors such as signssymptoms and clinical and family history, a doctor may suspect a particular cause of liver disorder and order follow-up tests. Some examples include:

Suspected type of liver disorder

Other or follow-up tests

Viral infection

Hepatitis AB, or C

Alcohol abuse/hepatitis

Ethanol

Toxic or drug-induced

Tests for toxins, drugs including drugs of abuse

Wilson's disease

CopperCaerulosplasmin

Autoimmune

ANASMA

Chronic

Liver biopsy

Liver cancer

AFP


Last Review Date: June 10, 2012