Gamma GT

What is Gamma GT (GGT)?

Gamma-glutamyl transferase (GGT) is an enzyme found mostly in the liver, but can also be present in the kidneys, pancreas, brain, and heart. It helps metabolise glutathione, a powerful antioxidant for detoxification, protecting against free radicals, and tissue repair^[1].

GGT is a reliable liver function biomarker and increases when damage to the liver or bile ducts is present^[1].

GGT cannot be used to determine the specific cause of liver disease, testing other liver biomarkers, such as alkaline phosphatase (ALP), will help with diagnosis.

Benefits of Testing Your Gamma GT

Gamma-GT is a good biomarker for detecting liver disease, especially alcohol-related liver disease. It can also help diagnose bile duct problems or blockages. A gamma-GT test is usually requested when someone is experiencing symptoms of liver damage or disease, such as jaundice, nausea, or vomiting.

GGT can be tested alongside alkaline phosphatase. If both biomarkers are raised it suggests bile duct disease or some specific liver diseases, such as cholestasis^[3].

To quantify gamma-GT levels, a blood sample is required. Test your gamma-GT levels at home by purchasing a simple at-home finger prick test. Collect your sample with the provided equipment and send it to one of our accredited laboratories for analysis.

GGT levels are tested as part of our:

• Liver Function Blood Test
• Baseline Health Check
• Ultimate Health Check 

What are normal GGT levels?

The following table shows the NHS gamma-GT reference ranges for men and women, and the average GGT collected from Forth customers. GGT levels are measured in international units per litre or IU/L.

The following graph and table displays the average GGT levels per age group.

Any result above the normal reference range may be considered dangerous and a sign that your liver is not working as it should be. The higher the level, the more profound the damage to your liver is likely to be.

If you receive an abnormal gamma-glutamyl transferase result, you should discuss your results with your doctor who can conduct further investigations. Your GGT results should be considered alongside symptoms, medical history, and other biomarker results.

What Causes High GGT?

Generally, high GGT levels are a sign of liver damage or a blockage in a bile duct, the tube that carries bile to the digestive organs. When the liver is damaged, it can leak substances, including enzymes, into the bloodstream. That’s why GGT is a good biomarker for liver disease, although it cannot specify which type of liver disease is present, further investigations are required for diagnosis.

There are several reasons why GGT levels can be increased, including:

• Non-alcoholic fatty liver disease
• Excessive alcohol consumption
• Hepatitis
• Kidney failure
• Chronic obstructive pulmonary disease
• Diabetes
• Obesity
• Heart failure or heart attacks
• Bile duct blockages
• Medicines such as phenytoin, non-steroidal anti-inflammatories (NSAIDs), antibiotics, and antidepressants^[4]

Symptoms of High GGT

Because high gamma-glutamyl transferase levels are usually a sign of liver disease, symptoms can include:

• Yellowing skin and whites of the eyes (jaundice)
• Itchy skin
• Feeling tired and weak
• Low appetite
• Low libido
• Feeling or being sick^[5]

In the early stages of liver damage, many people do not experience any symptoms. However, once signs appear, this signifies that damage and scarring have already occurred. This is called cirrhosis. Although research is ongoing, cirrhosis is not usually reversible, but there are things you can do to help manage the symptoms and slow down the progression of liver disease.

How To Keep GGT in the Healthy Range

If the cause of GGT is because of high consumption of alcohol or non-alcoholic fatty liver disease, there are lifestyle changes you can make to help improve the symptoms or manage the condition.

Unlike other organs, the liver has a unique mechanism to repair itself after damage, but this is limited. Many liver diseases can cause damage that is beyond repair, that’s why it is important to look after it before damage occurs.

How to reduce your GGT levels

Here are some of the proactive ways you can help to keep your GGT levels within a normal range:

• Reduce your alcohol intake: Alcohol is the most common cause of liver disease in the UK^[7], so cutting back on your intake or abstaining from alcohol completely is one of the best ways to look after your liver. Find out how alcohol impacts the body and how you can give up with our blog.
• Eat a healthy diet: Research shows that the Western Diet which is typically high in fat and sugar can increase the risk of developing non-alcoholic fatty liver disease (NAFLD)^[8]. A diet rich in whole and natural foods, such as fruits, vegetables, and whole grains is linked to lower GGT levels. The Mediterranean Diet is linked to lower rates of NAFLD^[9].
• Weight loss: Obesity and being overweight are risk factors for liver disease^[10]. A 2023 study found that a 15% weight loss improved non-alcoholic steatohepatitis with fibrosis in obese adults^[11].
  Take part in physical exercise: Exercise is proven beneficial for physical and mental wellbeing, but it’s also associated with a reduced risk of developing liver disease^[12]. Exercise is a useful therapeutic strategy for people with fatty liver disease because it can reduce the amount of fat in the liver^[13].
• Quit smoking: Cigarette smoking raises GGT levels. The more cigarettes you smoke, the higher your levels are likely to be^[14].

What are the treatments for high GGT?

Treatments for high GGT will depend on the underlying cause of liver damage. Following further tests your doctor may recommend certain medications to treat the condition and lifestyle changes like those listed above.

If you are displaying the symptoms of cirrhosis, you may be prescribed:

• Creams to ease skin itching
• Diuretics in combination with a low-salt diet lower the amount of fluid in the body to manage any swelling
• Medicines to manage high blood pressure in the main vein that transports blood to the liver, called liver hypertension^[15]

Written by Leanne Edermaniger

Based in the UK, Leanne specialises in writing about health, medicine, nutrition, and fitness.

She has over 5 years of experience in writing about health and lifestyle and has a BSc (hons) Biomedical Science and an MSc Science, Communication and Society.