The liver enzyme that tracks more than your liver

GGT shows up on many standard liver panels, usually next to the more familiar ALT and AST, and it's easy to assume it only matters if something is wrong with your liver. But this enzyme helps manage glutathione, one of your body's main antioxidants, and its level in your blood turns out to reflect a lot about your broader metabolic health. It's also one of the markers most responsive to everyday habits, which makes it a useful way to see whether the changes you're making are showing up inside your body.

The Basics

What it is

Gamma-glutamyl transferase is an enzyme found mostly in the liver and bile ducts. When liver cells are under stress or bile flow is blocked, more of it spills into your bloodstream.

Why it matters

In large population studies, higher GGT, even toward the upper end of the normal range, is associated with greater risk of heart disease, type 2 diabetes, and metabolic syndrome. It can also rise before other liver enzymes do, including in early fatty liver.

Healthy range

Reference ranges vary by lab, sex, and age, so go by the range on your own report. In general, values in the lower part of the normal range are associated with lower risk.

What moves it

Alcohol is the biggest everyday driver. GGT is sensitive enough to drinking that it's used to monitor it. Excess belly fat, ultra-processed foods and added sugar, smoking, and some medications can also raise it, while weight loss, a Mediterranean-style diet, and coffee are associated with lower levels.

When to test

It's included in many liver panels, so check whether it's on your last results. Skip alcohol and intense exercise for at least a day beforehand, since both can temporarily push it up.

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