GGT Blood Test Explained

GGT blood test measures the level of gamma-glutamyl transpeptidase (GGT) or gamma-glutamyl transpeptidase (GGTP) in the blood. GGT is a naturally occurring enzyme in the blood and is produced by many body organs (e.g. pancreas, kidney, spleen) with the liver as the major source. Increased GGT level in the blood is associated to liver damage and obstruction of the gall bladder. It is also associated to congestive heart failure and alcohol abuse.

Although increased GGT level in the blood may indicate liver damage, it does not indicate what causes the damage. The test result would not tell if the increased in GGT is caused by hepatitis, cirrhosis, gallstone, cancer, or any other type of liver disease. GGT is the first liver enzyme to soar up in the blood when the bile ducts are obstructed. Moreover, the higher blood GGT level, the greater is the damage to the liver.


Besides from liver damage, congestive heart failure, and alcohol consumption, there are certain medications that could increase blood GGT. These medications include carbamazepine, phenytoin, barbiturates, NSAIDs, lipid-lowering drugs, histamine blockers, antibiotics, anti-fungal agents, hormones, contraceptives, and antidepressants. Taking these medications before the test may affect the result of GGT blood test. Smoking can also increase blood GGT.

Normal level of GGT in blood

The normal level of GGT in females under the age of 45 ranges from 5 to 27 Units/Liter (U/L). In males and females over the age of 45, the normal blood GGT level ranges from 6 to 37 U/L. Children have the same blood GGT values as adults.

Other use of GGT

GGT blood test is ordered when a patient has a high alkaline phospatase (ALP; another liver enzyme) level in his blood. When ALP is high but the GGT is still normal, the increased in ALP indicates bone disease. But if both ALP and GGT are high, it indicates liver damage.[ad#afterpost]