A GGT blood test is used to measure the amount of the enzyme gamma-glutamyl transferase (GGT) in the blood. This article discusses how the test helps detect liver diseases.
Gamma-glutamyl transferase (GGT) is an enzyme that is present in the kidney, liver, spleen, gallbladder, and pancreas. However, this enzyme in blood mainly comes from the liver. It promotes the glutathione metabolism and the transfer of amino acids and peptides to cells. A GGT test helps find out the exact cause of elevated alkaline phosphatase (ALP), the enzyme required for proper metabolism of the body. ALP is present in the bones, liver, bile ducts, kidneys, placenta, intestinal lining, almost in every tissue. Liver diseases and bile duct obstruction leads to high ALP and high GGT levels, while bone diseases result in high ALP levels only. The increased levels of gamma-glutamyl transferase enzyme indicate that some underlying medical condition is causing damage to the liver; however, it does not specifically determine which condition it is.
Causes of High GGT Levels in Blood
The following factors or medical conditions may raise the level of this enzyme in blood:
- Liver or bile duct dysfunction resulting out of acute damage
- Obstruction of the bile duct (the cause can be tumors, stones, etc.)
- Consumption of alcohol (the levels are high in chronic drinkers compared to acute ones)
- Cholangitis, obesity, and drug abuse
- Congestive heart failure
Causes of Low GGT Levels in Blood
The following factors or medical conditions may lower the level of this enzyme in blood:
- Low thyroid levels
- Hypothalamic malfunction
- Severe deficiency of magnesium
When is the Test Ordered
Doctors may order this test if they notice high ALP levels in a patient. It may be ordered along with or as a follow-up to other liver enzyme function tests if a person experiences symptoms of liver disease or liver injury such as:
- Yellowish skin and eyes (jaundice)
- Light-colored stools
- Dark-colored urine
- Increased fatigue
- Loss of appetite
- Nausea and vomiting
- Itching sensation
- Pain or swelling in abdomen
Normal Levels
Normal GGT levels for children are similar to those for adults. However, in case of newborns, the normal range is almost five times as high as for an adult. The following reference GGT values may vary from lab to lab:
| Description | GGT Level |
| Normal Adult Female Range | 0 – 45 UL |
| Normal Adult Male Range | 0 – 65 U/L |
| High GGT for women younger than 45 years | GGT > 27 U/L |
| High GGT for men and women older than 45 years | GGT > 38 U/L |
Interference of Medications with GGT Levels
GGT levels are usually measured after fasting for at least eight hours because the levels drop after meals. You should inform your physician about your routine medications before the blood test since certain medications like NSAIDs, antibiotics, anti-seizure drugs, antifungal agents, antidepressants, etc., may increase the levels. Use of clofibrate, which is an anti-cholesterol medication and birth-control pills may decrease the levels.
Usually, the GGT levels are checked along with AST (Aspartate Transaminase) or ALT (Alanine Transaminase) levels. If elevated levels of AST and/or ALT are noticed, then the GGT numbers certainly help predict liver stress or liver damage.
Disclaimer: This HealthHearty article is for informative purposes only, and should not be used as a replacement for expert medical advice.
