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Gamma-glutamyl transferase
A liver and bile duct enzyme, sensitive to alcohol and to blocked bile flow.
Other names: GGT, gamma-glutamyl transpeptidaseSection: Blood chemistry
Updated: August 29, 2026·MedProtect editorial team Reference information — not a diagnosis or a prescription
In shortA common adult reference range is 5–40 U/L. GGT rises with liver or bile duct problems and with alcohol use; low or normal values argue against liver disease.
Reference ranges
Group
Reference range
Adults
5–40 U/L
Normal value ranges vary slightly among laboratories, and some labs use different measurement methods. The reference range on your report is the one that applies.
Check your value
Enter the number from your lab report — see how it compares with the typical range. Mind the units shown in the chosen row.
A rough comparison with a typical range, not a diagnosis. Reference ranges vary between laboratories — check the range on your own report and let a clinician interpret the result.
What this marker is
GGT (gamma-glutamyl transferase) is an enzyme found in high levels in the liver, kidney, pancreas, heart, and brain. In practice its blood level is used to detect diseases of the liver and the bile ducts — the small tubes that carry bile out of the liver.
The test has a classic pairing: measured together with alkaline phosphatase (ALP), it helps separate liver problems from bone disease. A high ALP with a high GGT points to the liver or bile ducts; a high ALP with a normal GGT points at bone. On its own, GGT cannot say which condition is present, but its level roughly tracks the amount of liver damage.
GGT is also used to screen for or monitor alcohol use, because alcohol is one of the strongest influences on this enzyme. Several medicines raise or lower it as well, which is why the medication list matters when the result is read.
Blood is drawn from a vein in a few minutes. Your provider may ask you to pause medicines that affect the test — but no medicine should be stopped without talking to the provider first.
When it is high
Blocked bile flow (cholestasis)When bile cannot leave the liver freely, GGT rises. This is one of the enzyme's most characteristic signals.
Alcohol useAlcohol raises GGT directly, and the test is used to screen for and monitor alcohol use. Alcohol use disorder is a common cause of a high value.
Hepatitis and cirrhosisA swollen, inflamed, or scarred liver releases more GGT, as it does with the other liver enzymes.
Liver-toxic medicinesMedicines and drugs that are toxic to the liver — including acetaminophen, carbamazepine, phenytoin, and phenobarbital — can raise the level.
Diabetes and heart failureGGT also climbs in diabetes and in heart failure, so a high value is not always a liver story.
Other causesPancreatitis and other pancreas disease, lung disease, reduced blood flow to the liver, liver tissue death, and liver cancer or tumors can all raise GGT.
When it is low
Low or normal usually means a healthy liverA low or normal GGT generally argues against liver disease. Birth control pills and clofibrate can lower GGT, so a low value can also be a medicine effect.
What can skew the result
These factors can shift the value without any disease — worth considering before a retest:
AlcoholAcetaminophen, carbamazepine, phenytoin, phenobarbitalBirth control pills and clofibrate (can lower values)
How to prepare
Tell your provider about every medicine you take. Your provider may ask you to pause medicines that affect the test; do not stop any medicine on your own.
When a retest makes sense
GGT is repeated and read together with alkaline phosphatase: the combination separates liver or bile duct causes from bone causes. If alcohol is the suspected driver, the trend after a period without alcohol is informative.
Who usually reviews this result
A result outside the reference range is usually reviewed by: your GP or primary care doctor; a gastroenterologist or hepatologist if liver or bile duct disease is suspected. Bring your lab report and any previous results to the appointment.
Names used on lab reports
Your report may use any of these names: GGTGamma-glutamyl transpeptidaseGGTPGamma-GTGTP
Units
Measured in: U/L
Several markers on your report?
See how MedProtect explains results in the app: the whole report, a check of the recognized values, and a clear breakdown.
Alkaline phosphatase rises in both liver and bone disease, while GGT rises mainly in liver and bile duct problems. High ALP with high GGT means the liver is the likely source; high ALP with normal GGT points to bone.
Does alcohol really raise GGT?
Yes. Alcohol is one of the best-known influences on GGT, and the test is used to screen for and monitor alcohol use. Certain medicines — acetaminophen, carbamazepine, phenytoin, phenobarbital — can raise it as well.
Is a high GGT dangerous by itself?
GGT is a marker, not a disease. A high value tells the provider to look for the cause — bile flow, alcohol, medicines, or another condition — using your symptoms, history, and the other blood tests.
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