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Overview

What Is a GGT Blood Test?

A GGT blood test measures the amount of gamma-glutamyl transferase in a sample of blood. This enzyme is also called gamma-glutamyl transpeptidase or gamma-glutamyl transferase and is associated mainly with the liver and bile ducts.

Clinicians use GGT results with your symptoms, medical history, and other liver tests to investigate liver or bile-duct conditions. The result may also help explore possible reasons for an abnormal liver test, but it does not diagnose a specific condition by itself.

When It Is Needed

When Is a GGT Test Needed?

A clinician may order a gamma GT test when symptoms suggest a liver or bile-duct problem. These symptoms can include jaundice, dark urine, pale stools, abdominal discomfort, itching, nausea, or unexplained fatigue. The test may also be considered when there is concern about impaired bile flow or an abnormal result on another liver test.

  • Investigating symptoms that may involve the liver or bile ducts.
  • Following up on abnormal liver-function test results.
  • Helping interpret an elevated alkaline phosphatase result.
  • Assessing possible alcohol-related liver injury or ongoing liver concerns.

Preparation

How to Prepare for a GGT Blood Test

Some laboratories ask patients to fast for a specified period before a GGT test, while others do not. Follow the instructions from the clinician who ordered the test or from the laboratory rather than fasting automatically. If you are unsure, ask before your appointment.

During the Test

What Happens During a GGT Blood Test?

A healthcare professional cleans the skin and inserts a small needle into a vein, usually in your arm. Blood is collected into one or more tubes and sent to a laboratory for analysis. This is a brief, single-session blood draw.

You may feel a brief pinch or sting when the needle enters the vein. Mild tenderness or bruising can occur afterward; applying pressure to the puncture site for a few minutes can help stop minor bleeding.

Risks

Risks of a GGT Blood Test

  • Brief pain or stinging when the needle is inserted.
  • Mild bruising, soreness, or small amounts of bleeding at the puncture site.
  • Lightheadedness or fainting during or shortly after the blood draw.
  • Rarely, infection or persistent bleeding at the puncture site.

Get medical advice

Watch the blood-draw site

Seek medical advice if bleeding does not stop with pressure or if you develop increasing redness or swelling, pus, or worsening pain at the puncture site.

Results

Understanding GGT Test Results

Your report gives a numeric GGT value and a reference range established by that laboratory. Reference ranges can vary between laboratories and may also be affected by patient factors, so there is no single universal cutoff for every person.

What a high GGT result may mean

An elevated GGT can occur with liver or bile-duct disease, alcohol use, certain medicines, and other conditions. A high GGT does not identify the cause on its own, so clinicians compare it with alkaline phosphatase, ALT, AST, bilirubin, your symptoms, and your medical history. They may also recommend repeat testing or imaging when appropriate.

Diseases & Conditions

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