Liver Function Test

Also known as:

  • LFTs
  • Liver Panel

Why Get Tested

To screen for, detect, evaluate, and monitor acute and chronic liver inflammation (hepatitis), liver disease and/or and damage

When to Get Tested?

Periodically to evaluate liver function; whenever you are at risk for liver injury;
when you are taking medications that may affect your liver;
when you have a liver disease;
when you have symptoms associated with liver damage, such as jaundice

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

  • People who take medications that may potentially damage the liver
  • Those who are alcoholics or heavy drinkers
  • Those who have a history of known or possible exposure to hepatitis viruses
  • Individuals whose families have a history of liver disease
  • People who are overweight, especially if they have diabetes and/or high blood pressure

A liver panel may be ordered when a person has signs and symptoms of liver disease; however, most people who have liver disease do not have any of these symptoms until the disease has been present for many years or is very severe. Some of these include:

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

Usually no one single set of liver tests is used to make a diagnosis. Often, several liver panels will be ordered over a few days or weeks to help determine the cause of the liver disorder and evaluate its severity.

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

Sample Required?

A blood sample drawn from a vein in your arm

Test Preparation Needed?

No preparation is needed.

What is being tested?

A liver panel is a group of tests that are performed together to detect, evaluate, and monitorliver 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 metabolizes 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 (hepatitis), scarring (cirrhosis), bile duct obstructions, liver tumors, 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, itching (pruritus), nausea, fatigue, diarrhea, and unexplained weight loss or gain emerge. Early detection is essential in order to minimize damage and preserve liver function.

The liver panel measures 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 typically 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 but also produced by the bones, intestines, and during pregnancy by the placenta (afterbirth); often increased when bile ducts are blocked
  • Aspartate aminotransferase (AST) – an enzyme found in the liver and a few other organs, particularly the heart and other muscles in the body
  • Bilirubin – two different tests of bilirubin often used together (especially if a person has jaundice): total bilirubin measures all the bilirubin in the blood; direct bilirubin measures a form that is conjugated (combined with another compound) in the liver
  • Albumin – measures the main protein made by the liver; the level can be affected by liver and kidney function and by decreased production or increased loss
  • Total protein (TP) – measures albumin and all other proteins in blood, including antibodies made to help fight off infections

Depending on the doctor and the laboratory, other tests that may be included in a liver panel are:

  • Gamma-glutamyl transferase (GGT) – another enzyme found mainly in liver cells
  • Prothrombin time (PT) – the liver produces proteins involved in the clotting (coagulation) of blood; the PT measures clotting function and, if abnormal, may indicate liver damage.

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 AnxietyTips on Blood TestingTips 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.

How is it used?

A liver panel may be used to screen for liver damage, especially if someone has a condition or is taking a drug that may affect the liver. A comprehensive metabolic panel (CMP) which is often performed as part of a general health checkup, may be ordered instead of a liver panel for routine screening. This group of tests includes most of the liver panel as well as additional tests that evaluate other organs and systems within the body.

A liver panel or one or more of its component tests may be used to help diagnose liver disease if a person has symptoms that indicate possible liver dysfunction. If a person has a known condition or liver disease, testing may be performed at intervals to monitor liver status and to evaluate the effectiveness of any treatments. A series of bilirubin tests, for instance, may be ordered to evaluate and monitor a jaundiced newborn.

Abnormal tests on a liver panel may prompt a repeat analysis of one or more tests, or of the whole panel, to see if the elevations or decreases persist and/or may indicate the need for additional testing to determine the cause of the liver dysfunction.

What does the test result mean?

Liver panel test 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 liver panels 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.

This table 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 Albumin
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
Chronic forms of various liver disorders Normal or increased Mildly or moderately increased Normal to slightly increased Normal
Alcoholic Hepatitis Normal or increased AST is moderately increased, usually at least twice the level of ALT Normal or moderately increased 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 Normal or decreased
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
Cancer that has spread to the liver (metastasized) Usually normal Normal or slightly increased Usually greatly increased 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 Normal or decreased
Autoimmune Normal or increased Moderately increased; ALT usually higher than AST Normal or slightly increased Usually decreased

If a person is taking drugs that may affect their liver, then abnormal test results may indicate a need to reevaluate 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 or damage is 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 (10x or more than ULN) 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, cirrhosis, liver cancer, and also with bone disease.

Aspartate aminotransferase (AST)
A very high level of AST(10x or more than ULN) 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 be low due to decreased production.

Total protein (TP)
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 with conditions, such as congestive heart failure.

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 virus testing, and may order a liver biopsy and/or imaging scans to help confirm a diagnosis and determine the extent of liver damage.

1.  Why does my doctor want to know all of the medications and supplements I am taking?

Your doctor will want to evaluate everything you are taking as a whole. Many over-the-counter drugs and herbal or dietary supplements have the potential to affect the liver. Excessive amounts of a drug, and/or a decreased ability to metabolize a drug, and/or a combination of drugs (including over-the-counter drugs and supplements) may injure the liver. For instance, both excessive acetaminophen use and the combination of acetaminophen and alcohol can cause severe liver damage.

2.  Can I have liver disease if I feel fine?

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

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

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

4.  Why is my family history important?

Some liver conditions, such as hemochromatosis and Wilson disease, may be inherited and can progressively damage the liver. Early detection of these conditions allows them to be treated and managed appropriately.

5.  What tests may be done in follow up to an abnormal liver panel 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 ABC, or E
Alcohol abuse/hepatitis GGTEthanol
Toxic or drug-induced Tests for toxins, drugs including drugs of abuse
Wilson disease CopperCerulosplasmin
Autoimmune ANAASMA
Chronic Liver biopsy
Liver cancer AFPDCP