Gamma-Glutamyl transferase (GGT) Test

The GGT test helps to detect liver disease and bile duct injury. Doctors can also use the test to help find out the reason for a raised concentration of alkaline phosphatase (ALP) within the bloodstream. Both ALP and GGT are elevated in disease of the bile ducts and in some liver diseases, but only ALP will be elevated in bone disease. If the GGT concentration is normal in a person with a high ALP result, the cause is most likely to be bone disease. GGT can also be used to screen for excessive alcohol consumption (it will be elevated in about 75% of long-term drinkers).

A doctor usually requests GGT along with other tests to evaluate a person who has signs or symptoms that suggest liver disease. Some of the symptoms of liver injury include jaundice, nausea, vomiting, abdominal (around the stomach area) swelling, abdominal pain, pruritus (severe itching), and tiredness.

GGT is increased in most diseases that cause damage to the liver or bile ducts, but is usually not helpful in distinguishing between different causes of liver damage as a single test. However there are studies that indicate GGT can be used together with other markers as diagnostic scores to predict the presence of liver fibrosis and also for non-alcoholic fatty liver disease. In people with a history of alcohol abuse who are undergoing treatment, GGT may be used to check that the person is following the treatment program properly.

Your doctor is not usually concerned with low or normal results, but they do tell him/​her that it is unlikely that you have liver disease. Oral contraceptives (birth control pills) and clofibrate can decrease GGT concentrations.

Raised GGT concentrations may indicate that something is going on with your liver, but not specifically what. In general, the higher the result the greater the damage to your liver.

Raised GGT is also commonly found due to drinking excess alcohol, and the use of many prescription and non-prescription drugs including nonsteroidal anti-inflammatory drugs (NSAIDs), lipid-lowering drugs, antibiotics, histamine blockers (used to treat excess stomach acid production), antifungal agents, anticonvulsants (seizure control medications), antidepressants, and hormones such as testosterone.

Alcohol consumed within 24 hours of your GGT test may cause a temporary increase in the GGT result, if you consume alcohol regularly. If this occurs, your doctor may want to repeat the test to verify the result.

Smoking may also increase GGT concentrations.

Levels of GGT increase with age in women, but not in men, and are always somewhat higher in men than in women.

Several drugs increase (induce) the concentration of GGT in the blood. The increases do not indicate damage to the liver. Please inform your doctor of any prescription or non prescription drugs that you are taking.

Yes, GGT is very sensitive and can be increased when you don’t have symptoms. This elevation may be temporary, perhaps due to medications you are taking or alcohol ingested within 24 hours of the test. If other liver enzymes are normal, your doctor may just wait and then repeat the GGT test. If the GGT is very high and/​or your other liver enzymes are raised, your doctor may want to do more extensive testing to search for the cause.

Over time, your GGT level will fall from whatever level it was at the time when you stopped drinking alcohol to a near normal state. It takes at least a month and sometimes longer for GGT to return to normal after you stop drinking. Abstaining from alcohol will decrease your chances of further damaging your liver and should allow your liver functions to improve.