Lab marker

GGT

Gamma-glutamyl transferase · γ-GT

Sensitive to liver injury and alcohol use — and independently predicts all-cause and cardiovascular mortality.

Moderate relevance4 cited sourcesNo fastingBundled; €5–15 standalone.nutrition

What it measures

An enzyme present on the surface of hepatocytes and biliary epithelium; elevated when hepatobiliary cells are stressed or proliferating. Reported in U/L. More sensitive than ALT to alcohol and biliary causes; also rises with hepatic steatosis, certain medications, and oxidative stress.

Reference context

3 guideline sources

GGT values within the lab 'normal' range still carry mortality signal — Ruttmann 2005 showed graded mortality risk across quartiles entirely within normal. Useful as a trend marker even when not clinically abnormal.

Population context — consult guideline targets below

Mechanism

Why moving this marker matters

Beyond its role as a liver-injury marker, GGT participates in extracellular glutathione metabolism and is associated with oxidative stress. Ruttmann et al. 2005 (Circulation, n=163,944 Austrian adults followed for 17 years) demonstrated a strong dose-response between baseline GGT and cardiovascular mortality independent of traditional risk factors. The relationship persists across multiple cohort meta-analyses.

Guideline targets

What major guidelines recommend

Common reference (men)

Moderate

<55 U/L (assay-dependent)

Common reference (women)

Moderate

<38 U/L (assay-dependent)

Risk-association threshold

Moderate

Values in the upper-normal quartile (~30–55 U/L men, ~25–38 U/L women) associated with elevated CV mortality vs lower quartiles in cohort data

How to measure

The test, where to get it, when to repeat

Method

Standard liver panel item. Fasting not required.

Where

GP standard panel or private lab.

Typical cost

Bundled; €5–15 standalone.

Fasting

Not required

When to test

AASLD 2017 (Kwo)
Helpful when characterising hepatobiliary patterns alongside ALT, AST, ALP. Routine isolated screening not recommended.

Where to test

Independent labs offering this test

Healicus refers you to independent laboratories. You order from the lab; they take the sample, run it, and return your result on their own platform. Healicus never sees your value.

Healicus is not the provider. Your contract for the service is with whoever you choose. Links labelled Sponsored are paid affiliate relationships; unlabelled links are editorial reference only. See our disclosure for the full policy.

Context

Reading the numbers

Caveats

Many medications induce GGT independently of liver injury (antiepileptics, statins, some antibiotics). Recent alcohol intake elevates GGT meaningfully. Interpret in context.

Practices

What's been shown to influence this marker

Reducing alcohol consumption reliably lowers GGT within 4–8 weeks; abstinence reduces it further.

Limit alcohol intake

Habit·Lancet pooled analysis (n=599,912): lowest mortality risk threshold is ~100 g/week — about 5-6 standard drinks total.

Strong evidence

Why

Wood et al. 2018 Lancet combined individual-participant data from 83 prospective studies (n=599,912 current drinkers in 19 high-income countries). Above ~100 g/week (about 5-6 UK standard units), all-cause mortality climbs in a dose-response manner. Below that threshold the curve is roughly flat — there is no protective effect. Reductions from heavier intake to ≤100 g/week could add up to 2 years of life expectancy at age 40.

How to do it

How

Track intake honestly for one week. If above threshold, set a weekly cap rather than a daily one (avoids the 'I'll catch up' trap). Several alcohol-free days per week is the simplest pattern. Sleep quality typically improves within 1-2 weeks of reduced intake.

Ideal for

Anyone currently drinking above ~100 g/week (≈one bottle of wine, six pints of beer, or a half-bottle of spirits).

Markers this may influence

Ferritin Triglycerides eGFR ALT GGT PSA Folate Iron studies Haemoglobin & CBC uACR Blood pressure AUDIT-C hsCRP

Caution: Sudden cessation in heavy drinkers can cause withdrawal — taper or seek medical guidance if you've been drinking heavily for years.

Evidence

Wood et al., Lancet 2018 — pooled analysis of 83 prospective studies (n=599,912 current drinkers)

Practising under

Mediterranean dietary pattern

Habit·Olive oil, fish, nuts, legumes, plants. The most-studied diet for cardiovascular and cognitive longevity.

Strong evidence

Why

The Mediterranean pattern — heavy on plants, olive oil, fish, nuts, legumes; moderate fish and dairy; light on red meat — has the strongest evidence base of any specific diet for long-term cardiovascular and cognitive outcomes. PREDIMED, the largest trial, showed ~30% reduction in major cardiovascular events vs. low-fat control.

Slot in your day

With a meal

How to do it

How

Olive oil as the primary fat. Plants at every meal. Fish 2–3× per week. Nuts daily (small handful). Red meat once a week or less. Wine optional, with food.

Sticking with it

Stock the kitchen for one week's pattern. Decisions live in the shopping list, not at mealtime.

Evidence

Estruch et al., NEJM 2018 (PREDIMED)

Related markers

ALT→AUDIT-C→Triglycerides→

Take to your physician

Worth discussing

Whether your value reflects alcohol use, medication, hepatic steatosis, or biliary issue.
If persistently elevated above 2× ULN, what further workup is appropriate.
Whether your value fits with your other liver markers (ALT, AST, ALP) — pattern matters more than any single value.

Sources

Cited literature

Edited by Carl Pöhl, MD · Healicus editorial

Last reviewed May 2026

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