GGT

Blood test

Also known as: Gamma-glutamyl transferase, Gamma-GT

There is no agreed cutoff for GGT. Labs print a reference range, but it describes the people tested, not a healthy target.

GGT is an enzyme on the surface of liver cells, on the side that faces the bile ducts. It rises with alcohol, bile-flow problems, some medicines and several other conditions. Doctors use it as a supporting test, read alongside other liver tests.

What it tells you

Because it sits next to the bile ducts, it rises along with alkaline phosphatase when bile flow is blocked.
Its main job is to show whether a high alkaline phosphatase comes from the liver. A high GGT alongside it points to the liver.
It is not a screening test for liver disease on its own. The American College of Gastroenterology advises against using it that way when other liver tests are normal.
It can be one clue to heavy drinking. It is raised in more than half of people with alcohol problems, even without obvious liver disease.
It does not come from muscle. After heavy weightlifting, ALT and AST rose for a week, but GGT stayed normal.
Higher GGT goes with higher risk of death, diabetes and heart disease, even inside the range labs call normal. That is a link, not a target.

What can throw it off

Alcohol raises it.
Some medicines raise it, including phenytoin and barbiturates.
Blocked bile flow raises it, usually along with alkaline phosphatase.
Pancreatic disease, a heart attack, kidney failure, emphysema and diabetes can raise it.
Heavy exercise does not raise it, unlike ALT and AST.

Evidence

Spotting heavy drinking

Some human evidenceCEBM Level 2b

In 1,250 men who drank, GGT told harmful from moderate drinking apart only moderately well. In 402 people with alcohol dependence, a raised GGT missed 70% to 80% of self-reported heavy drinking. A normal GGT does not rule out a drinking problem.

Predicting death, diabetes and heart disease

Strong human evidenceCEBM Level 1a

Across 19 studies of 9.24 million people, the top third of GGT had 1.6 times the death risk of the bottom third. The top third also had about 1.3 times the risk of type 2 diabetes. These are links only; no trial shows that lowering GGT changes outcomes.

Limits

It is not specific. Alcohol, bile-flow problems, medicines and diseases outside the liver all raise it.
It is not a screening test for liver disease when other liver tests are normal.
It is not a reliable alcohol test. A normal GGT does not rule out a drinking problem, and a high one does not prove one.
Its links with death, diabetes and heart disease are associations. There is no evidence that a person's GGT should be treated as a target.
No healthy number exists. The range printed on a lab report is not a goal.

References

Reviewed by Shubham Gupta, MD — Founder & President · November 1, 2026

This page is for education only. It is not medical advice. Decisions about any treatment belong with a physician who knows your history.