A GGT blood test is commonly ordered to evaluate liver injury or biliary obstruction, conditions that usually cause elevated GGT levels. It is often requested alongside other liver tests, such as AST, ALT, bilirubin, and ALP, to support a more accurate diagnosis.
Gamma-glutamyl transferase is an enzyme produced mainly by the liver, pancreas, and heart, and its levels may rise when these organs are affected by conditions like cirrhosis, fatty liver disease, pancreatitis, or excessive alcohol use. Because GGT is not specific to one disease, results are always interpreted together with symptoms, imaging tests, and additional blood tests.
The GGT blood test may be part of a routine evaluation or ordered when liver disease is suspected based on symptoms such as jaundice, abdominal pain, dark urine, or low energy. The test also requires specific preparation, including fasting and avoiding alcohol, and normal values usually range between 7 and 50 IU/L, depending on the lab running the test.
Interpreting results
GGT levels should always be interpreted by a healthcare professional, ideally the clinical who ordered the test. Abnormal GGT results may occur for several reasons, including:
High GGT
Elevated levels are usually a sign of a liver problem, such as:
- Chronic viral hepatitis;
- Decreased blood flow to the liver;
- Liver tumor;
- Cirrhosis;
- Excessive alcohol or drug use.
The GGT test is not specific to any single disease and results should be interpreted alongside other tests to confirm a diagnosis, These may include imaging studies (such as a CT scan or ultrasound) and additional blood tests.
Liver disease symptoms that may accompany an elevated GTT result include right-sided abdominal pain and abdominal swelling.
In rare cases, GGT can also become high due to non-liver conditions, like cardiac failure, diabetes or pancreatitis.
Low GGT
Low GGT levels on their own are not of clinical significance and do not indicate any type of liver issue or alcohol use disorder.
However, patients with low GGT levels and high ALP levels may have another condition, such as a bone or musculoskeletal disorder, vitamin D deficiency, or Paget’s disease, which should be confirmed through additional testing.
Preparing for the test
You should fast for at least 8 hours before this blood test, since eating can temporarily lower GGT levels. Avoid drinking alcohol for 24 hours beforehand, as it can affect the results. Certain medications may also need to be paused before the test because they can raise GGT levels.
Be sure to tell the lab technician and your doctor when you last drank alcohol so they can consider it when interpreting your results.
Indications for testing
The GGT test is usually ordered when a doctor suspects a liver injury, especially if the patient presents with symptoms like:
- Notably decreased appetite;
- Nausea and vomiting;
- Decreased energy;
- Abdominal pain;
- Yellow skin and eyes;
- Dark urine;
- Pale stools;
- Itchy skin.
A GGT test may also be ordered to monitor liver function for people who are detoxing from alcohol.