GGT (gamma-glutamyl transferase)

GGT (gamma-glutamyl transferase) is an enzyme found mainly in the liver and bile ducts, but also in the kidneys, pancreas and other organs. High GGT most often suggests liver strain or impaired bile flow, and frequently rises because of alcohol, certain medicines and fatty liver. The test is very sensitive but does not show the cause, so it is interpreted alongside other liver results.

Who the test is for

• people having general or preventive check-ups, as part of liver testing alongside ALT and AST;
• people with symptoms suggesting liver or bile duct disease: fatigue, nausea, pain under the right rib cage, yellowing of the skin and eyes, dark urine or pale stools;
• people with high alkaline phosphatase of unclear cause;
• people receiving treatment for excessive alcohol consumption;
• people taking long-term medicines that may affect the liver, such as certain epilepsy medicines.

If yellowing of the skin and eyes occurs with severe abdominal pain or fever, see a doctor immediately.

What GGT indicates

GGT rises even with mild liver and bile duct damage, often before other liver enzymes. It is therefore a useful but non-specific indicator: a high result shows that something is burdening the liver, but not what. The highest values usually occur with impaired bile flow, for example due to a stone or narrowed bile ducts.

GGT also helps identify the source of high alkaline phosphatase. If both alkaline phosphatase and GGT are high, the cause is probably in the liver or bile ducts. If only alkaline phosphatase is high and GGT normal, bone is a more likely source, which can be clarified by bone-specific ALPtesting.

Save with a panel

Test GGT (gamma-glutamyl transferase) is also included in these panels.

Liver health panelAST, ALT, GGTPrice of individual tests: 9.60€9.00€Details ›Extended liver health panelAST, ALT, AP, GGT, total bilirubin, total protein17.00€Details ›General preventive panelCBC, glucose, cholesterol, HDL and LDL cholesterol, triglycerides and 430.00€Details ›

All panels including GGT (gamma-glutamyl transferase) (21) ›

Preparation and sample

Blood is taken from a vein. Fasting is not essential for GGT alone, but liver tests are often performed in the morning alongside fasting tests such as glucose, lipids or PT; follow their instructions in that case. Avoid alcohol for at least a day beforehand because even a small amount can temporarily raise GGT. Tell your doctor which medicines and supplements you take.

What high GGT means

The reference interval depends on sex, age and method and is printed on the report; men generally have slightly higher values than women. GGT is physiologically higher in newborns and infants and falls towards adult levels during the first months of life.

Most common causes

• Alcohol: regular drinking is one of the most common causes of high GGT. After stopping, at least a month and sometimes longer is needed for the value to return to normal.
• Fatty liver: with excess weight, diabetes and high triglycerides, GGT is often mildly elevated.
• Medicines: some epilepsy medicines (e.g. phenytoin and carbamazepine), barbiturates and other medicines can raise GGT even without liver damage.
• Liver disease: viral, alcoholic or toxic hepatitis, cirrhosis and liver tumours or metastases.
• Bile duct disease: bile duct stones, inflammation or narrowing.
• Other causes: pancreatic disease, heart failure and some kidney diseases; smoking can also mildly raise GGT.

Mildly high GGT with otherwise normal results is common and does not necessarily mean liver disease. A doctor usually repeats testing after several alcohol-free weeks and, if it remains high, investigates further, for example with bilirubin, alkaline phosphatase, hepatitis markers and liver ultrasound (we performabdominal ultrasound only in Split). An Extended Liver Health Panelis also available for broader assessment. Low GGT has no clinical significance.

How to arrange testing

You can have blood taken without an appointment or referral at one of our branches across Croatia (listed on the Contact page). Prices for all tests and panels are available in the service price list. GGT is most often measured as part of the Liver Health Panel, together with AST and ALT.

Frequently asked questions

Can GGT be high if I do not drink alcohol?

Yes. Common causes include fatty liver, excess weight, diabetes, medicines and bile duct disease. High GGT is therefore not proof of alcohol consumption and is interpreted alongside other findings.

How quickly does GGT fall after stopping alcohol?

Gradually. Usually at least a month of abstinence, and sometimes longer, is needed for GGT to return to the reference interval. If it still does not fall, a doctor seeks another cause.

Is high GGT a sign of liver cancer?

Most often not. GGT can be high with liver tumours, but much more often because of alcohol, fatty liver or medicines. GGT is not a tumour marker. We discuss symptoms requiring examination in First signs of liver cancer.

What is the difference between GGT, ALT and AST?

ALT is found mainly in liver cells and rises when they are damaged. AST also occurs in muscles and the heart, so rises after substantial exertion too. GGT is most sensitive to bile duct changes, alcohol and certain medicines. A doctor therefore usually considers all three together.