Gamma-Glutamyl Transferase (GGT): Test and Results

What Is GGT?

GGT, or gamma-glutamyl transferase, is an enzyme mostly found in your liver, but it's also present in your kidneys, pancreas, and other organs. It helps move substances in and out of cells and supports the body in breaking down toxins.

This enzyme plays a major role in managing glutathione, a substance that protects cells from damage. Because GGT is closely linked to liver function, doctors often check its level to detect liver or bile duct problems.

When liver cells are injured or bile flow is blocked, GGT levels usually go up. This makes GGT an important biomarker for spotting liver disease, alcohol-related damage, or bile duct issues early.

When Is GGT Testing Recommended?

Doctors may order a GGT test to check for liver damage or bile duct problems. It’s also useful when other liver test results are unclear.

You may need a GGT test if you:

• Have symptoms of liver disease, such as fatigue, nausea, dark urine, or yellowing of the skin (jaundice).
• Consume alcohol regularly, especially in large amounts.
• Take medications that can affect the liver.
• Have abnormal results on other liver tests, like ALT or ALP.
• Are being monitored for liver health during ongoing treatment.
• Have a history of liver or bile duct disorders in your family.

How Is GGT Testing Conducted?

GGT is measured through a blood test. A healthcare provider draws a small amount of blood from your vein, usually in your arm. The sample is then sent to a lab for analysis.

GGT may be included in a liver panel, comprehensive metabolic panel (CMP), or enzyme tests that check overall liver function.

Preparation for the test

• You may be asked to avoid eating or drinking for up to 8 hours before the test.
• Avoid alcohol for at least 24 hours, as it can affect the results.
• Always tell your doctor about any vitamins, herbs, or supplements you're taking.

What Are the Normal GGT Levels?

Normal GGT levels can vary depending on age, sex, and lab methods, but here are common reference ranges:

For adults: 5 to 40 U/L

Note: The units of measurement and the normal ranges can differ depending on the laboratory and the specific methods used.

What Do Abnormal Levels Mean?

GGT High Levels

High GGT levels often point to liver or bile duct problems. They may also rise due to lifestyle habits or certain health conditions.

Possible causes include:

• Liver disease: GGT increases when liver cells are damaged.
• Blocked bile ducts: GGT rises if bile cannot flow normally.
• Heavy alcohol use: Alcohol can irritate the liver and raise GGT levels.
• Fatty liver disease: Linked to obesity and poor diet.
• Heart failure: Reduced blood flow to the liver may affect GGT.
• Smoking: Tobacco use can influence liver enzyme levels.

To manage high GGT levels:

• Limit or stop alcohol use completely.
• Eat a liver-friendly diet, rich in fruits, vegetables, and lean proteins.
• Exercise regularly to maintain a healthy weight.
• Avoid unnecessary medications or supplements unless prescribed.
• Quit smoking, if applicable.
• Follow up with your doctor to find and treat the cause.

GGT Low Levels

Low GGT levels are usually not a concern. They are less common and rarely cause symptoms or require treatment.

Possible causes include:

• Healthy liver: A normal, low level often means your liver is functioning well.
• Magnesium deficiency: Rarely, low magnesium can affect enzyme levels.
• Hypothyroidism: An underactive thyroid may slightly reduce GGT.

If your GGT is low:

• Continue healthy habits like balanced eating and regular activity.
• Discuss thyroid health or other possible causes with your doctor.
• Track GGT levels if advised during routine health checkups.

Which Specialist Should You Consult?

If your GGT levels are abnormal, you may need to see a:

• Primary care doctor: For general evaluation and guidance.
• Gastroenterologist: Specializes in liver and digestive issues.
• Hepatologist: Focuses specifically on liver diseases.

These professionals can help you understand your results, order follow-up tests, and guide your next steps.