Other names: Gamma-Glutamyl Transferase

GGT is an enzyme, which is predominantly found in the liver; small amounts are usually present in the blood. GGT levels increase if the liver is damaged or there is a blockage, which is obstructing the flow of bile.

Why is the test used?

The test is primarily used to detect problems with the bile duct and liver disease. The test can also be used to measure levels of ALP (alkaline phosphatise); levels of both GGT and ALP rise when a patient has diseases which affect the bile duct or the liver but only ALP levels increase when the patient has bone disease. The GGT test is also used to test for alcohol abuse; levels are higher in those who drink heavily on a regular basis.

The test is usually ordered when a doctor suspects that a patient has liver disease; symptoms include jaundice, vomiting and nausea, abdominal pain and inflammation and lethargy. The test may also be used when a patient is undergoing a course of treatment for alcohol abuse; the test helps to monitor the patient’s condition and helps doctors to see if the patient is following the programme correctly.

How is the test done?

The test is carried out by using a needle to collect a sample of blood from the arm; a needle in inserted into the vein and the blood is drawn out and collected in a syringe. Once the sample has been collected, it will be placed in a bottle, labelled and sent away to the laboratory for analysis.

What do the test results show?

Low or normal levels are usually not a cause of concern; however, they usually indicate that a patient has not got liver disease.

High levels of GGT indicate damage to the liver; the test cannot diagnose a specific condition but very high levels of GGT indicate severe damage to the liver. High levels may indicate liver disease, but they may also be associated with alcohol abuse and congestive heart failure; certain types of medication, including antibiotics, histamine blockers, NSAIDs (non-steroidal anti-inflammatory drugs) and anticonvulsants, may also cause levels of GGT to increase.

Oral contraceptives may cause GGT levels to decrease.

Smoking can cause levels of GGT to increase and drinking even a small amount of alcohol may affect the test result; this is why it is important to avoid drinking alcohol for 24 hours before the test.

Specific Blood Tests

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