GGT

What it actually measures

GGT sits on the surface of cells in your liver and bile ducts, and its day job is part of how your body recycles glutathione.

Glutathione is your main intracellular antioxidant, and GGT is the enzyme that breaks down glutathione outside the cell so its components can be taken back in and reassembled. That is a maintenance role rather than a damage one.

Which gives this marker two separate meanings, and they are worth keeping distinct.

The first is the conventional one. GGT rises when the liver and bile ducts are irritated, and it is particularly sensitive to alcohol and to anything obstructing bile flow. That makes it useful alongside ALT, because the two respond differently to different insults.

The second is more interesting and less certain. Because GGT is central to glutathione turnover, a raised level is sometimes read as reflecting increased oxidative stress, meaning the body is working harder at antioxidant recycling.

That second reading is mechanistically coherent and is not as firmly established as the first, which is worth knowing before anyone sells you a supplement on the strength of it.

Why it is the honest one about drinking

GGT has a reputation, and the reputation is earned.

It is more sensitive to alcohol than ALT is, which means it often rises with drinking at a level that leaves other liver enzymes unmoved. That sensitivity is why it is used clinically when alcohol intake is in question.

It is not perfectly specific, and I would not want anyone reading a raised GGT as proof of anything about their drinking. Bile duct obstruction raises it, several medications raise it, and metabolic fatty liver raises it.

But the pattern is informative. A GGT that is raised while ALT sits normal, in someone with no obstructive symptoms, is a picture worth being honest with yourself about.

The metabolic connection deserves its own note. A raised GGT frequently travels with insulin resistance, excess visceral fat and the rest of the metabolic picture, and it is one of the components used in some fatty liver indices.

So the useful reading is not GGT in isolation. It is GGT alongside ALT, alongside your triglyceride to HDL ratio, alongside an honest account of your drinking.

One more practical point. GGT responds to changes in drinking over weeks rather than days, which makes it a genuinely useful marker to recheck after a period of abstinence.

What moves it

Down: reducing or stopping alcohol, which is the most direct lever and shows up within weeks. Losing excess visceral fat. Improving insulin sensitivity. Treating the underlying cause of any bile flow problem. Stopping a contributing medication, which is a prescriber decision rather than a self-directed one.

Up: alcohol, more sensitively than for any other common liver enzyme. Bile duct obstruction, including gallstones. Metabolic fatty liver. Several medications including some anticonvulsants, barbiturates and others. Smoking. And increasing age and body weight generally.

The honest hedge

I am not a doctor and I am not diagnosing anyone.

The first thing worth saying is that a raised GGT is not proof of drinking, and I would not want this page used to draw that conclusion about anyone. Bile obstruction, medications and metabolic fatty liver all raise it, and any of them can be the explanation.

The second is that a markedly raised GGT, particularly alongside raised alkaline phosphatase or any jaundice, points toward bile flow obstruction and belongs with a doctor promptly rather than being watched.

On the oxidative stress reading, I want to be measured. The mechanistic link through glutathione metabolism is real. The leap from a raised GGT to a specific antioxidant supplement recommendation goes considerably further than the evidence, and it is a leap the supplement industry makes constantly.

There is also a hard truth worth stating plainly. If alcohol is the reason, no supplement addresses that, and the marker responds to the one intervention people least want to be told about.

That is not a lecture, and it is the honest reading of what this number is most sensitive to.

So. What to actually do.

Tonight, at no cost. Find your GGT and your ALT on the same panel and look at them together. Raised GGT with a normal ALT is a specific pattern worth noticing.

Count your drinks honestly for a fortnight. Not from memory, written down as they happen. Most people are surprised, and this is the marker that notices.

Run the experiment if the pattern fits. Four to six weeks without alcohol, then retest. GGT responds on that timescale, which makes it one of the more satisfying markers to move.

Check the metabolic picture. Fasting insulin with HbA1c, since a raised GGT frequently travels with insulin resistance and visceral fat.

See a doctor promptly for a markedly raised value, especially with raised alkaline phosphatase, pale stools, dark urine or any yellowing. That points at bile flow rather than at lifestyle.

Review your medication list with a prescriber. Several drugs raise GGT, and that is a real explanation rather than an excuse.

Do not buy a glutathione supplement on the strength of this number alone. The mechanism is real, the recommendation goes further than the evidence.

You are not being judged by an enzyme. You are running a recycling system that happens to leave a measurable trace, and the trace is unusually honest about one particular input.

Your body is not broken. It is blocked. And sometimes the block is the thing you would least like the test to be sensitive to, which is precisely why it is worth reading rather than explaining away.

Go count a fortnight, written down.