The short answer
GGT (gamma-glutamyl transferase) is an enzyme associated with the bile ducts and liver cell membranes. It is sensitive but not specific: it can rise with alcohol, certain medicines, bile flow problems and metabolic liver disease, so it is used mainly to help interpret other results.
What is happening?
A raised ALP together with a raised GGT suggests the ALP is coming from the liver or bile ducts rather than bone.
GGT also tends to be higher with regular alcohol intake and with some enzyme-inducing medicines.
Why does this matter?
An isolated mildly raised GGT is common and often does not indicate serious liver disease — but it should be interpreted, not ignored.
Population studies have also reported associations between GGT and cardiometabolic risk, though GGT is not used as a cardiovascular test.
What does the evidence say?
The interpretive role of GGT in distinguishing hepatobiliary from bony ALP elevation is standard clinical practice described in the MSD Manual.
Key takeaway
GGT is a sensitive clue rather than a verdict — its value comes from the company it keeps on the report.
Sources & references
American College of Gastroenterology
ACG Clinical Guideline: Evaluation of Abnormal Liver Chemistries (2017) · Clinical guideline
View original sourceUS National Library of Medicine (MedlinePlus)
AST Test · Official health information
View original sourceAmerican Association for the Study of Liver Diseases
AASLD Practice Guidance on the clinical assessment and management of nonalcoholic fatty liver disease (2023) · Clinical guideline
View original source
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