Gamma-Glutamyl Transferase (GGT)
GGT is a liver enzyme measured by a standard blood test - a raised level is often the first clue to fatty liver, and it tends to fall as you lose weight.
Plain English
Patient-Friendly Explanation
Gamma-glutamyl transferase, usually just called GGT, is an enzyme found mainly in the liver and bile ducts. It shows up on a routine liver panel - the same blood test that reports ALT and AST - and it is one of the more sensitive early signals that something is happening in the liver. In weight management the commonest reason for a mildly raised GGT is fat accumulating in the liver, which is very common in people carrying excess weight, particularly around the abdomen. Alcohol, some medicines, gallstones and other liver conditions can raise it too, so an abnormal result is interpreted alongside your history, your other liver tests and often a liver ultrasound. A single number is much less useful than the trend, which is why we repeat it. The good news is that it responds well to lifestyle change: losing 7 to 10 per cent of body weight, cutting back on alcohol and sugary drinks, and moving more usually brings GGT down within a few months.
Medical
Clinical Definition
Gamma-glutamyl transferase is a membrane-bound enzyme that catalyses the transfer of the gamma-glutamyl moiety of glutathione to acceptor peptides or L-amino acids, functioning in glutathione recycling and amino acid transport. It is present in hepatocytes, biliary epithelium, kidney, pancreas and intestine, and is measured in serum as part of standard liver panels. In metabolic liver disease it is typically raised in MASLD, and rises in parallel with hepatic fat content, HOMA-IR and alcohol intake; it is a component of several non-invasive fibrosis and steatosis indices, including the Hepatic Steatosis Index and the Fatty Liver Index, and of the GGT-to-platelet-ratio and AST-to-ALT/GGT combinations used in risk stratification. GGT is more sensitive than ALT to early steatosis and to alcohol-related liver injury, but it is not specific: cholestasis, biliary obstruction, cardiac failure, obesity itself, hypothyroidism, and enzyme-inducing drugs such as phenytoin, carbamazepine and phenobarbital all raise it. Values in the high-normal range, even within the reference interval, predict incident type 2 diabetes, metabolic syndrome, hypertension and cardiovascular events in prospective cohorts, reflecting its association with oxidative stress and insulin resistance rather than liver injury alone. Interpretation therefore requires the full panel, alcohol history, medication review and, where indicated, hepatic imaging; weight reduction of 7 to 10 per cent reliably lowers GGT and improves steatosis on imaging.
Key Insight
Why It Matters
GGT is part of the metabolic screen we run at your first visit, and it is one of the clearest signals of how much fat is sitting in the liver. Watch it fall over the first few months of your programme - it usually does before the bathroom scale moves much.
Sources
Reviewed against standard medical references.
Medically reviewed by
Family Physician & Registered Acupuncturist, Accord Medical Clinic. MBBS (NUS), Graduate Diploma in Family Medicine (NUS), Graduate Diploma in Acupuncture (Singapore College of TCM).
Last reviewed: September 2026
This page is general health education, not medical advice. Whether any treatment is appropriate for you is a decision made in consultation after assessment.
