GGT is an enzyme abundant in the liver and bile ducts. It is a very sensitive but not very specific marker: it reacts to almost any liver trouble, but on its own it does not say which kind.
The main value of GGT is in combination: it helps tell whether an elevated alkaline phosphatase is of liver origin, and it is especially sensitive to alcohol.
Reference ranges
Approximate reference for adults (venous blood):
| Men | up to 55 U/L |
| Women | up to 38 U/L |
| Feature | the liver enzyme most sensitive to alcohol |
What an elevated level means
GGT rises in a wide range of conditions:
Alcohol — the best-known cause; GGT reacts even to moderate regular use.
Bile stasis — stones, narrowing of the bile ducts; then alkaline phosphatase rises in parallel.
Fatty liver and medications — very common causes.
An isolated high GGT in someone who feels perfectly well is most often related to alcohol or fatty liver — worth reviewing your lifestyle and retesting.
What a low level means
A low GGT has no clinical significance and is regarded as a favorable sign.
How the test is done
Venous blood, fasting, in the morning.
For 3–7 days before the test avoid alcohol — GGT falls slowly, and even a few days of "sobriety" noticeably affect the result.
What affects the value
- Alcohol — the main factor; GGT falls only weeks after stopping.
- Bile stasis — stones and narrowing of the bile ducts.
- Fatty liver — a common cause of a mild rise.
- Medications — many induce GGT.
- Sex — the normal range is higher in men.
Calculate using this marker
Calculators where GGT (Gamma-glutamyl transferase) is used directly:
Frequently asked questions
GGT is high — does that mean I drink a lot?
Not necessarily. GGT is indeed very sensitive to alcohol, but it can also be raised by fatty liver, medications and bile stasis. It is an "alarm" marker: it signals that the liver is unhappy about something, but does not name the cause.
Why test GGT together with alkaline phosphatase?
Alkaline phosphatase rises with both liver and bone disease. If GGT is elevated at the same time, the source is most likely the liver or bile ducts. If GGT is normal, bone should be considered.
How do I lower GGT?
Give up alcohol (the effect is visible in 2–4 weeks), lose weight if you have fatty liver, and review medications with your doctor. GGT responds well to lifestyle change.