Gamma-glutamyl Transferase (GGT) Test
Reviewed
This test measures the amount of GGT in your blood. GGT is an enzyme mainly found in your liver. High levels may be a sign of liver disease or damage to the bile ducts. The test cannot diagnose the specific cause.
Preparation and collection
Talk to your provider about specific instructions. Some medicines, supplements, alcohol, or smoking may affect results. GGT levels drop after meals, so your provider may ask you to fast for a certain amount of time before testing.
Understanding this test
Use the reference interval and units printed by the laboratory that performed the test. A result outside that interval is not a diagnosis by itself, and a result inside it does not rule out every condition. Your symptoms, history, medicines, timing, and related tests can change what the result means.
- Cannot diagnose the specific cause of liver disease; only indicates liver damage.
- Results may be affected by certain medicines, supplements, alcohol, smoking, or recent meals.
- Provides no information about bone disorders without comparison with an ALP test.
What to do next
Your healthcare provider will interpret your GGT results along with your symptoms, medical history, and other liver function tests (e.g., ALP, ALT, AST, LDH) to understand your condition.
Evidence source
U.S. National Library of Medicine: Gamma-glutamyl Transferase (GGT) Test