Lab test glossary · Liver
GGT: what it means
Also known as: gamma-glutamyl transferase, GGTP
GGT is a liver enzyme sensitive to bile-duct problems and alcohol; it's often used to clarify what's driving a high alkaline phosphatase.
What it measures
GGT (gamma-glutamyl transferase) is an enzyme found in the liver and bile ducts. It's especially useful as a tie-breaker: when alkaline phosphatase is high, a raised GGT suggests the source is the liver or bile ducts rather than bone. It's also sensitive to alcohol.
Typical range
Often roughly 5–40 U/L, varying by lab and sex.
Reference ranges differ between labs and are printed on your own report — always read your result against that range, not a general one.
What a high result can mean
- Alcohol intake
- Bile-duct blockage or liver conditions
- Fatty liver disease
- Some medications
A high value is a starting point for a conversation, not a diagnosis — many causes are benign or temporary.
Why the trend matters
GGT responds to recent alcohol and liver stress, so its trend across draws is a fairly direct readout of change.
When to talk to your doctor
Discuss a persistently elevated GGT with your doctor, particularly alongside a high alkaline phosphatase or other liver tests.
This page is general education about a common lab test — it isn’t medical advice and can’t interpret your specific result. What a value means depends on your history, symptoms, and the rest of your labs, which is a conversation for you and your clinician.