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[Biochemistry](https://durgical.com/en/biochemistry/) · Topic

# Gamma-glutamyl transferase (GGT) as a lab test

GGT is very sensitive to cholestasis and alcohol but not specific; its main use is confirming that a high ALP is from the liver.

Updated 2026-11-01

## Key facts

- A membrane enzyme that transfers the γ-glutamyl group of glutathione; it takes part in glutathione recycling.
- It is found in liver, bile ducts, kidney and pancreas, but not in bone: so it separates hepatic from bone ALP.
- It is induced by alcohol and by enzyme-inducing drugs (phenytoin, carbamazepine, barbiturates).
- It is very sensitive but not specific: it rises in fatty liver, obesity, diabetes and heart failure.
- Its reference range varies by laboratory and sex.

## In detail

- What it measures: the activity of γ-glutamyl transferase, which cleaves extracellular glutathione so its amino acids can re-enter cells.
- Where it comes from: mainly bile canaliculi and ducts; also the proximal renal tubule (but renal GGT goes into urine, not blood).
- Why it rises: cholestasis of any cause, alcohol use, inducing drugs, fatty liver, hepatitis, liver metastases.
- Pitfalls: an isolated mild GGT rise with nothing else is common and rarely means serious disease; an alcohol-related rise takes weeks to settle after abstinence.
- It has been studied as a marker of cardiometabolic risk and oxidative stress, not as a diagnostic test for those diseases.

**Also called**
GGT, γ-GT, Gamma-GT

## Clinical notes

- High ALP with normal GGT points to bone, pregnancy or growth.
- In progressive familial intrahepatic cholestasis types 1 and 2, GGT is normal despite cholestasis: a useful exception.
- It is used, with MCV and other markers, to follow alcohol abstinence.

## Related conditions

- [Cirrhosis](https://durgical.com/en/conditions/cirrhosis/)
- [Choledocholithiasis](https://durgical.com/en/conditions/choledocholithiasis/)
- [Acute cholangitis](https://durgical.com/en/conditions/acute-cholangitis/)
- [Metabolic syndrome](https://durgical.com/en/conditions/metabolic-syndrome/)

## Related

- [Alkaline phosphatase (ALP) as a lab test](https://durgical.com/en/biochemistry/topics/alkaline-phosphatase-as-a-lab-test/)
- [Liver function tests: reading the pattern](https://durgical.com/en/biochemistry/topics/liver-function-tests-reading-the-pattern/)
- [Glutathione (GSH)](https://durgical.com/en/biochemistry/molecules/glutathione/)

## Test yourself

Think of the answer, then tap the question to see it.

## What is GGT mainly used for in practice?

To confirm that a high alkaline phosphatase comes from the liver and not bone, because bone has no GGT.

## Which substances induce GGT?

Alcohol and enzyme-inducing drugs such as phenytoin, carbamazepine and barbiturates.

## Why is GGT not specific?

It rises in many settings: fatty liver, obesity, diabetes, heart failure, alcohol and drugs, as well as cholestasis.

## Which molecule is GGT's natural substrate?

Glutathione: GGT removes its γ-glutamyl group so its amino acids can be recycled.

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Educational information, not medical advice. For any symptom, see a health professional.

Sources: [Gamma-glutamyl Transferase (GGT) Test: MedlinePlus Medical Test](https://medlineplus.gov/lab-tests/gamma-glutamyl-transferase-ggt-test/) (MedlinePlus, US National Library of Medicine, 2026); [Gamma-glutamyl transferase (GGT) blood test: MedlinePlus Medical Encyclopedia](https://medlineplus.gov/ency/article/003458.htm) (MedlinePlus, US National Library of Medicine, 2026); Textbook of Biochemistry for Medical Students, 6th ed. (Jaypee Brothers Medical Publishers (Vasudevan DM, Sreekumari S, Vaidyanathan K), 2011).

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