In the GGT (gamma-glutamyl transferase) test, a healthcare professional measures the levels of GGT in a sample of blood. High levels of GGT in the blood can indicate damage to the liver or bile ducts. Normal ranges suggest that there is no liver damage.
This article looks at the purpose and procedure of the GGT test, normal GGT ranges, and what abnormal ranges can mean.
Normal GGT ranges
If a doctor suspects that a person has liver disease, they may order a GGT test.
The liver contains the highest levels of GGT, while the blood and some other organs contain minimal quantities.
High levels of GGT in the blood could indicate that the enzyme is leaking out of the liver cells and into the blood, suggesting damage to the liver or bile ducts.
A typical range for GGT levels in adults and children is between 0 and 30 international units per liter (IU/L). Newborn infants will have significantly higher levels right after birth.
A person with a normal GGT test probably does not have liver disease. When someone who is in treatment for alcohol use disorder has a normal reading, this likely means that they have not had an alcoholic drink recently.
GGT levels will rise according to the amount of liver damage a person has.
High GGT levels indicate that something is damaging the liver, though it does not diagnose the specific problem. A person will often need follow-up tests to find out the reasons for the elevated GGT levels.
A doctor may order a GGT test as part of regular blood testing during a yearly physical examination, if a person is taking a medication that has potentially toxic effects on the liver, or if someone has symptoms of liver disease.
Symptoms of liver damage
Symptoms of liver damage include:
- jaundice, which causes yellow skin, eyes, or mucous membranes
- dark urine
- abdominal pain
- light-colored stool
Causes of liver damage
Diseases that can cause liver damage include:
What causes high GGT levels?
GGT levels may increase for many reasons, so a doctor will usually use the GGT test in conjunction with other tests for diagnosis.
Liver or bile duct damage
GGT levels are usually the first to rise when a person has a bile duct obstruction, making this the most sensitive liver enzyme test for detecting problems with the bile duct.
The GGT test is also part of a series of tests known as a liver panel, which checks the levels of other liver enzymes, such as alanine aminotransferase (ALT), aspartate aminotransferase (AST), alkaline phosphatase (ALP), and bilirubin.
Someone with an elevated ALP level may need a GGT test to narrow down the cause.
Bone disease and liver or bile duct disease can lead to elevated ALP levels. Having a GGT test can distinguish between the two: a normal GGT level likely indicates a bone issue, while a high GGT level may signal a problem with the liver or bile ducts.
Chronic alcohol abuse
GGT levels tend to be higher in people who regularly drink heavily compared with people who drink in moderation or only drink heavily on occasion. Because of this, a doctor may measure GGT levels to test for acute or chronic alcohol abuse.
Doctors may use the test to monitor alcohol use in someone who is receiving treatment for alcohol abuse disorder or hepatitis due to chronic alcohol use.
Procedure and what to expect
The GGT test is a simple and safe procedure that usually provides results within a couple of days.
The GGT test is a simple blood test.
During the test, the healthcare professional will tie a band around the upper arm, clean the inner elbow thoroughly with an alcohol pad, and insert a small needle into the skin. They will collect a small tube of blood.
After the test, they will remove the needle and band and will apply pressure to the site to make sure any bleeding stops.
As with any other blood test, the blood draw may cause minor, temporary discomfort, which will pass quickly.
The healthcare professional will label the sample and send it to a lab for testing. The lab should produce the results within a day or two, though it may take a little longer for the doctor to receive and interpret the results.
Risks and side effects
Having a blood draw is a very safe procedure. Some people get some bruising at the needle insertion site after the test. It is also normal to be a little sore for a short time after the test.
Occasionally, a person may feel faint or anxious during the test, causing them to black out or faint. Though this can be frightening, it does not indicate a serious reaction.
A GGT test measures the levels of GGT in the blood. This test helps a doctor diagnose liver damage.
There are many potential causes for elevated GGT levels. It is essential to follow up with the doctor as instructed to determine the cause of the result, and discuss treatment options if needed.