Overview

A gamma-glutamyl transferase (GGT) blood test is a simple test to check the health of your liver and bile ducts. Bile ducts are thin tubes that carry a fluid called bile from your liver to your small intestine.

GGT is a protein in the blood, called an enzyme. It's mostly found in the liver and bile ducts. If your liver or bile duct cells are damaged, this protein can leak into your bloodstream. So your GGT level goes up.

A GGT test usually isn't done by itself. It's often part of a group of tests called a liver panel or liver function tests. These tests look for many other substances related to liver health. Examples include alanine aminotransferase (ALT), bilirubin, and alkaline phosphatase (ALP).

Other names for a GGT test are:

Gamma-glutamyltransferase.
Gamma-glutamyl transpeptidase (GGTP).
Serum GGT.
Gamma-GT.

Why it's done

A gamma-glutamyl transferase (GGT) test helps look for liver or bile duct disease. The test may be done as part of routine blood work to check your general health.

Your healthcare professional may check your GGT level and other liver enzymes if you have symptoms of liver or bile duct disease such as:

Weakness or tiredness that you can't explain.
Loss of appetite.
Nausea or vomiting.
Pain in the right upper belly.
Swelling of the belly.
Itching.
Dark urine.
Light-colored stools.
Yellowing of the skin or whites of the eyes, called jaundice.

You may need a GGT test if you have:

Alcohol-related liver disease.
A blockage in the bile ducts.
Other liver or bile duct disease.
A high alkaline phosphatase (ALP) level.

Healthcare professionals usually test GGT and ALP together. That's because ALP can come from the liver or bones, but GGT comes mostly from the liver and bile ducts. So comparing both helps your healthcare team learn where any change is coming from. For instance, if your GGT is OK but your ALP is high, it may mean a bone condition is the cause.

A healthcare professional also may do a GGT test to check for alcohol misuse or to see if treatment for an alcohol-related condition is working.

Why it's not done

A gamma-glutamyl transferase (GGT) test is not recommended to:

Check for liver disease when other liver function tests are OK.
Look for liver cancer in people who do not have symptoms.

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Risks

There's little risk in getting a gamma-glutamyl transferase (GGT) test. As with any blood test, possible risks may include:

Soreness or tenderness in the area where the blood is taken.
Bruising near the area where the blood is taken.
Bleeding.
Fainting or feeling lightheaded.
Infection of the area where the blood is taken. This is rare.

How you prepare

Most people don't need to do anything special to get ready for a gamma-glutamyl transferase (GGT) test. But here are a few things to keep in mind.

Alcohol. Your healthcare professional may ask you not to drink alcohol before the test. Even drinking a little bit of alcohol can raise your GGT level. How alcohol affects GGT levels may depend on a person's genes.
Medicines. Some medicines and supplements may affect your GGT level. Examples are phenobarbital and phenytoin (Dilantin, Phenytek). Tell your healthcare team about all the medicines and supplements you take. Include those you buy without a prescription.
Food and drinks. Your GGT level can go down after a meal or snack. Your healthcare team may ask you not to eat or drink anything for a short while before your test.

What you can expect

You take a gamma-glutamyl transferase (GGT) test at a medical office, clinic, hospital or lab. There are some at-home tests to check liver health, which may include a GGT test. But these tests may not be widely available.

During

A small sample of blood is needed to do a GGT blood test. If you're anxious about needles or have fainted during a blood test, tell your healthcare team. Also tell the team if you have a bleeding disorder.

To do a GGT test, the healthcare professional:

Cleans your skin with alcohol.
Uses a small needle to take blood from a vein, usually in your arm.
Puts a bandage on to prevent bleeding.

After

You might have a small bruise or feel sore where the needle went in. The bruise or discomfort usually goes away in a day or two. You usually can return to your daily activities right away.

Results

Your healthcare team talks with you about your gamma-glutamyl transferase (GGT) test results. Most people get their results in a few days.

Your healthcare professional looks at your GGT results along with other liver function tests such as ALT, ALP and bilirubin. When looking at your GGT results, keep these things in mind:

A slight rise in GGT may not be a concern.
One single GGT number doesn't tell the whole story. Your healthcare team compares the number to results from other liver function tests.
Foods, some medicines and alcohol can cause changes in GGT level.

Results of a GGT blood test are given in units per liter (U/L). The standard range is as follows:

GGT results for males

11 months and younger: less than 178 U/L.
12 months to 6 years: less than 21 U/L.
7 to 12 years: less than 24 U/L.
13 to 17 years: less than 43 U/L.
18 years and older: about 8 to 61 U/L.

GGT results for females

11 months and younger: less than 178 U/L.
12 months to 6 years: less than 21 U/L.
7 to 12 years: less than 24 U/L.
13 to 17 years: less than 26 U/L.
18 years and older: about 5 to 36 U/L.

Note: Lab ranges may differ depending on the lab doing the test. Ask your healthcare professional what the target GGT goal is for you.

Low GGT level

A low GGT level is usually not a reason to worry. It could mean that you did not drink alcohol or you do not have liver disease.

High GGT level

The GGT level often goes up when there is liver damage or changes with the flow of bile.

Possible causes of high GGT related to the liver or bile ducts include:

Blocked bile ducts due to stones or tumors.
Irritation and swelling of the liver, called liver inflammation.
Long-term, heavy alcohol use.
Medicines that can hurt the liver, such as phenobarbital and phenytoin (Dilantin, Phenytek) to treat seizures.
Metabolic dysfunction-associated steatotic liver disease (MASLD), formerly called nonalcoholic fatty liver disease (NAFLD).
Scarring of the liver, called cirrhosis.
Viral hepatitis.

A high GGT level is not always due to liver or bile duct disease. That's because some GGT also is found in the pancreas, kidneys and other areas. Other health conditions that can make your GGT level go up are:

Diabetes.
A lung condition called emphysema.
Heart attack or heart failure.
Kidney failure.
Irritation and swelling of the pancreas, called pancreatitis.

It's important to remember that a GGT test does not give your healthcare team one clear answer. It can't tell them exactly what is causing a high level. So a high GGT level by itself can't be used to diagnose a condition, such as liver disease or cancer.

Complications of high GGT

Having high GGT levels for a long time may be linked to other health conditions such as:

Heart disease.
Liver scarring.

Higher GGT levels also may raise your risk of some cancers, including:

Breast cancer.
Colorectal cancer.
Liver cancer.
Lung cancer.
Prostate cancer.

Researchers continue to study how GGT and cancer are connected. It is not clear whether GGT actually causes cancer or if GGT levels go up when the body is under physical stress.

If your GGT level is high, your healthcare team may:

Repeat the test in a few weeks.
Order other blood tests or imaging tests.
Talk with you about the medicines you take and how much alcohol you drink.
Send you to a liver specialist, if needed.

If you have questions about your test results or next steps, talk with your healthcare professional.

By Mayo Clinic Staff

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Doctors & Departments

April 03, 2026

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