What is GGT?

If you’ve just taken our Liver Blood Test or had a liver profile included as part of a health check-up, you may be wondering what some of the markers mean. 

This guide looks at gamma GT, also known as gamma-glutamyl transferase (GGT), its role in the body, and what it might signify if your levels are abnormal. 

• What is GGT?
• Why do I need a GGT test?
• What is a normal GGT level?
• What does a high GGT level mean?
• What does a low GGT level mean?
• What level of GGT is dangerous?
• How can I lower GGT levels?
• Looking after your liver
   

What is GGT?
 

Gamma-glutamyl transferase (GGT) is an enzyme found throughout the body but mostly in the liver. GGT helps the liver metabolise drugs and toxins.

If the liver is damaged, GGT levels may rise as it leaks into the bloodstream. Raised levels may be a sign of liver disease or damaged bile ducts [1]. The bile ducts are tubes that carry bile from the gallbladder to the intestines to assist with digestion.

A GGT result cannot diagnose the specific cause of liver problems, so it is normally carried out alongside other liver markers, such as alkaline phosphatase (ALP), or a scan.  
 

Why do I need a GGT test?
 

You may have a GGT test as part of a routine liver screen, like a Liver Blood Test, or as part of a full health MOT, such as an Advanced Well Man Blood Test or Advanced Well Woman Blood Test.

Alternatively, your doctor may request a GGT test if you have signs of liver disease. 

Signs of liver disease include:

• Fatigue
• Weakness
• Jaundice
• Abdominal pain
• Nausea or vomiting

GGT is also used to screen for or monitor alcohol abuse. As alcohol is broken down, it damages the liver cells, releasing GGT.

Abnormal results are most pronounced in chronic heavy drinkers, but even small amounts of alcohol can cause elevated GGT levels. A normal value does not necessarily rule out alcohol misuse, either. 

Find out about other harmful effects of alcohol on the body. 

 

What is a normal GGT level?
 

If taking a blood test with us, men should aim for a GGT value between 8 – 61 U/L, and women, between 6 – 42 U/L. Be aware that normal values vary slightly depending on the laboratory.
 

What does a high GGT level mean?
 

Raised levels of GGT are usually a sign of damage to the liver or a bile duct blockage. This is because when the liver is damaged, it can leak its contents, such as enzymes, into the bloodstream.

Some drugs or medical conditions, such as heart failure, may cause secondary damage to the liver, resulting in elevated GGT levels.

Causes of raised GGT levels: 

• Excessive or chronic alcohol consumption
• Fatty liver disease
• Hepatitis (liver inflammation)
• Liver cirrhosis (scarring caused by long-term damage)
• Bile duct blockages (usually caused by gallstones or tumours) 
• Heart failure
• Prescribed medications (such as antiepileptics, oral contraceptives, antibiotics, and antidepressants) 
• Some over-the-counter medications (such as non-steroidal anti-inflammatories or paracetamol, particularly high doses) [1]

If abnormal GGT levels are a side effect of medications, levels will begin to normalise once the drug is stopped.
 

What does a low GGT level mean?
 

A low or normal GGT result means that it’s less likely you have underlying liver disease. 
 

What level of GGT is dangerous?
 

Any GGT result above the normal range may be a sign that your liver is not working in the way it should. In general, the higher the result, the greater the damage to the liver.

If your result is abnormal, you should discuss this with your doctor who may advise further tests or scans. As GGT is a non-specific marker, the result should be taken into consideration alongside your symptoms and other results. 
 

How can I lower GGT levels?
 

Depending on the cause, you may be able to lower your GGT levels. 

Often a raised GGT is a result of alcohol-related liver damage or fatty liver disease. Both conditions may be improved through lifestyle changes. It may take a month or so before you start seeing an improvement. 

It’s important to look after your liver. It has a remarkable ability to repair itself, but only to a certain extent. Continued damage to the liver causes fibrosis (scarring), which can be irreversible and difficult to treat.

Ways you can improve your GGT level:

• Cut back on alcohol, or better still, stop drinking altogether — If you’re a drinker, the most effective thing you can do is to reduce your drinking. Alcohol can cause permanent damage to the liver over time. Visit the NHS website for tips on cutting down alcohol and useful contacts for alcohol problems.
• Eat a healthy diet — Avoiding foods high in saturated fats and increasing the amount of fruit and vegetables you eat can reduce your risk of fatty liver disease. The Mediterranean diet is particularly helpful in reducing liver fat [2]. 
• Exercise regularly — Even if you’re not losing weight, regular exercise can help with fatty liver disease [3]. 
• Lose weight if you’re overweight — Being overweight is a risk factor for developing fatty liver disease. Losing more than 10% of your body weight can help remove some of the fat in the liver [3].
   

Looking after your liver
 

An abnormal GGT result is usually indicative of damage to the liver. See our 7 ways to keep your liver healthy. 

Some causes of raised GGT can’t be fully corrected with lifestyle changes alone and may require medical treatment. For this reason, we recommend discussing any abnormal results with your doctor who will be able to advise on any next steps.
 

Related tests
 

Liver Blood Test — Our liver function profile can be carried out at home as a simple finger-prick test. It includes enzymes such as GGT and ALT to look at how well the liver is functioning.

Advanced Well Man Blood Test or Advanced Well Woman Blood Test — Our bestselling comprehensive health checks for men and women give a more detailed overview of not only your liver but the rest of your body. 

References
 

1. MedlinePlus, 2021. Gamma-glutamyl Transferase (GGT) Test. [online] MedlinePlus. Available at: <https://medlineplus.gov/lab-tests/gamma-glutamyl-transferase-ggt-test/> [Accessed 29 December 2021].
2. NICE, CKS. 2021. Scenario: Management | Management | Non-alcoholic fatty liver disease (NAFLD) | CKS | NICE. [online] Available at: <https://cks.nice.org.uk/topics/non-alcoholic-fatty-liver-disease-nafld/management/management/> [Accessed 29 December 2021].
3. NHS. 2018. Non-alcoholic fatty liver disease (NAFLD). [online] Available at: <https://www.nhs.uk/conditions/non-alcoholic-fatty-liver-disease/> [Accessed 29 December 2021].