Gamma-Glutamyl Transferase

Also written GGT

Organ functionMeasured in U/L

What it measures

An enzyme concentrated in the liver and biliary tract, sensitive to alcohol and to enzyme-inducing medications.

Why it matters

It helps distinguish liver from bone causes of a raised alkaline phosphatase, and it is a sensitive marker of alcohol consumption.

Where the claimed ranges actually sit

Measured in U/L. Each row is one claim about where your result should fall.

What a laboratory reportsWhat a seller markets as “optimal”

Laboratory reference range< 55 U/L

Laboratory reference intervals; sex-specific

Under 20 U/LC< 20 U/L

Longevity platforms and detoxification supplement marketing

›View as table

Claim	Range	Source
Laboratory reference range	< 55 U/L	Laboratory reference intervals; sex-specific
Under 20 U/L	< 20 U/L	Longevity platforms and detoxification supplement marketing

Where the sources disagree

The mortality association within the normal range is genuine and reproducible, which makes the marker interesting. What follows from it is not. There is no evidence that lowering GGT with a supplement changes anything; the association is most likely reflecting alcohol intake, adiposity, and oxidative stress, which are the actual things worth addressing.

The marketed ranges, examined

Each claim gets its strongest possible case before it gets its criticism. Several of these are substantially correct.

Under 20 U/L

Promoted by longevity platforms and detoxification supplement marketing

CConfounded

The strongest case for it

GGT within the conventionally normal range tracks with cardiovascular and all-cause mortality in large cohorts, and it is a sensitive marker of alcohol intake and oxidative stress.

What it leaves out

It is non-specific, raised alike by alcohol, medications, fatty liver, and biliary disease. Its main commercial use is as an entry point for 'detox' and liver-support supplements, a category with essentially no outcome evidence.

Before you act on your result

Highly sensitive to recent alcohol intake.
Raised by many common medications.
Non-specific in isolation; interpret with ALT and alkaline phosphatase.

Last reviewed July 28, 2026How we grade evidence and attribute claims →

More in Organ function

Alanine Aminotransferase

ALT

Estimated Glomerular Filtration Rate

eGFR

The Mirror Brief

One email when a reference range changes, a panel claim is corrected, or a regulatory status actually moves, not when something is merely proposed. No sponsors from any company we rate.

Unsubscribe anytime. We never sell or share your address.