What is gamma-GT?
Gamma-GT, gamma-glutamyltransferase, sits in the wall of the bile ducts and in the liver cells, where it helps recycle glutathione, the cell's main protector against oxidative damage. If those cells become irritated, it leaks into your blood. It responds to everything that burdens the liver, and earlier than ALT: with regular alcohol, with fat in the liver, with medicines the liver has to break down, and with a bile drainage that does not flow well. That sensitivity is also the limitation. A high gamma-GT says your liver or bile ducts are burdened, not by what, and the pattern with the other values points the way. High gamma-GT with high ALT is the liver; high gamma-GT with high ALP and bilirubin is the bile ducts; high gamma-GT with a normal ALT and an AST that rises more than ALT is alcohol; and high ALP with a normal gamma-GT is not liver but bone, because gamma-GT does not rise from bone problems. Your report shows gamma-GT in U/L. Normal is up to about 55 U/L for a man from age 19 and up to 38 U/L for a woman, and here the labs agree. A healthy liver sits well below that. The enzyme has a half-life of ten days or so, so a change in what you drink or take shows after a few weeks.
Why is gamma-GT relevant?
Gamma-GT is the most honest measure of what alcohol does to your liver. Alcohol switches on the production of the enzyme in the liver cells, and in anyone who drinks regularly the value sits high while ALT can still be normal. It does not respond to a single evening, but to the average of the last few weeks. That makes it the value that shows what a dry January or a month without delivers: in most people gamma-GT falls back to normal in four to six weeks, and that is a concrete result of a concrete decision. The second reason is that gamma-GT moves with the whole metabolic picture. Belly fat, insulin resistance, high triglycerides and fatty liver lift it, and a gamma-GT at the top of the band goes together with a higher risk of diabetes and cardiovascular disease, even within the normal band. The enzyme is a measure of oxidative stress, and it falls with weight loss, exercise and less sugar just as well as with less alcohol. The third reason is the bile drainage. Gallstones, a narrowing or an inflammation of the bile ducts let gamma-GT and ALP rise together, often with bilirubin alongside and complaints in the upper right of the abdomen. That is a different picture from liver strain, and the combination of gamma-GT and ALP tells the two apart without further investigation.
Gamma-GT reference ranges
What counts beside the number:
- ALT: if it rises with it, it is the liver; if it stays normal, it is usually alcohol or medicines
- ALP and bilirubin: if those rise with it, it is the bile ducts; high ALP with normal gamma-GT is bone
- AST relative to ALT, because with alcohol AST rises more
- How much you drank in recent weeks, not just yesterday
- Your waist and triglycerides, the company of fatty liver
- Which medicines you take, because a number switch on the enzyme without damage
Gamma-GT is one of the few liver values the labs agree on, and the limit sits lower in women than in men. There is no lower limit that means anything. Within the band too it matters where you sit: a gamma-GT at the top goes together with more belly fat and a higher risk of diabetes, and falls with the same lifestyle as alcohol. Always read gamma-GT beside ALT and ALP.
What Dutch labs actually use
0 – 38U/L
Outside this range every lab calls it abnormal.
every lab calls 0 – 38 U/L normal. Outside that range every lab calls it abnormal.
Every age, per lab
| Laboratory | Group | Reference range |
|---|---|---|
| Unilabs(Saltro, Medlon, SHO, Atalmedial)2026 | Men 11–18 yrs | 0–31 U/L |
| Women 11–18 yrs | 0–22 U/L | |
| Men 19+ | 0–55 U/L | |
| Women 19+ | 0–38 U/L | |
| Star-shl2026 | Men 13–18 yrs | 0–45 U/L |
| Women 13–18 yrs | 0–33 U/L | |
| Men from 18 yrs | 0–55 U/L | |
| Women from 18 yrs | 0–38 U/L | |
| Certe2026 | Men from 18 yrs | < 55 U/L |
| Women from 18 yrs | < 38 U/L | |
| Clinical Diagnostics2026 | Men | < 55 U/L |
| Women | < 38 U/L |
Each band as the lab publishes it, retrieved in 2026, unless marked otherwise.
Gamma-GT high or low: what it means
A high gamma-GT means liver or bile ducts under strain. In order of how often it occurs: alcohol, fatty liver, medicines, a congested bile drainage, and rarely heart failure, in which the liver sits full of blood through congestion. ALT and ALP point the way: high ALT alongside is the liver, high ALP alongside is the bile ducts, only gamma-GT high is usually alcohol or medicines. A slightly raised value with otherwise normal liver values is almost always lifestyle and falls within weeks. A low gamma-GT means nothing; it is not a deficiency and a low value is favourable rather than unfavourable. What you do about it: with alcohol, cutting down is the lever, and a month without usually lets the value fall considerably already; have blood drawn again after six weeks and you see it. With belly fat and fatty liver, weight loss, less sugar and soft drinks, and exercise are the levers. If you take something that burdens the liver, such as some drugs against epilepsy, the rise is explained by that and nothing needs doing. With a congested bile drainage, imaging of the bile ducts belongs. Always read gamma-GT beside ALT, AST, ALP and bilirubin, and with a rise beside your triglycerides and waist. Better to have blood drawn in an ordinary week than after a party weekend, unless you want to see exactly what that does.
What lowers it
Not a finding; little gamma-GT is a liver that is little burdened.
| Cause | How often |
|---|---|
| Naturally lowAnyone who drinks little, has little belly fat and takes no medicines sits low in the band, and that is the favourable side | Often |
What raises it
Liver or bile ducts under strain, and the question is by what.
| Cause | How often |
|---|---|
| AlcoholSwitches on the production of the enzyme; responds to the average of the last few weeks, not to one evening, and falls in four to six weeks without | Often |
| Fatty liverFat in the liver from belly fat, sugar and too little exercise; goes together with high triglycerides and a higher ALT | Often |
| MedicationDrugs against epilepsy, some antidepressants, the pill and statins switch on the production; an explainable rise without consequence | Sometimes |
| Blocked bile flowGallstones, a narrowing or an inflammation of the bile ducts; ALP and bilirubin rise with it, often with complaints in the upper right of the abdomen | Sometimes |
| Heart failureA heart that does not pump well leaves the liver full of blood, and the congested liver leaks gamma-GT | Rare |
How does a gamma-GT blood test work?
- Referral
- Not needed. Gamma-GT is in every liver panel you can have measured yourself, together with ALT, AST, ALP and bilirubin.
- Fasting
- Not needed. Gamma-GT barely moves with food.
- When
- In an ordinary week, not just after a party weekend, unless you want to see exactly what that does; the enzyme responds to the average of the last few weeks.
- The draw
- One tube of blood from a vein in your arm. The other liver values come from the same draw.
- Repeating
- Six weeks after drinking less or a change in medicines; then the value shows whether the switch has really been flipped.
- Which test
- Gamma-GT is in the comprehensive test (€229) and in .
- Where to draw
- You can draw at 250+ locations near you, no referral needed. See the locations
Frequently asked questions
What is gamma-GT?
An enzyme from the cells of your liver and bile ducts, which helps recycle glutathione, the cell's main protector against oxidative damage. It leaks into your blood as soon as those cells are irritated, and that happens with everything that burdens the liver: alcohol, fat, medicines and a bile drainage that falters. It responds earlier than ALT and says less about the cause.
What is a normal gamma-GT level?
Up to about 55 U/L for a man from age 19 and up to 38 U/L for a woman, and here the labs agree. A healthy liver sits well below that, and within the band too it matters where you sit: at the top gamma-GT goes together with belly fat and a higher risk of diabetes, at the bottom with a liver that is little burdened.
What does a high gamma-GT mean?
That your liver or bile ducts are burdened, and the company says by what. Only gamma-GT high, with a normal ALT, is usually alcohol or medicines. High with a high ALT is the liver, usually fatty liver. High with a high ALP and bilirubin is the bile ducts, with gallstones as the most common reason. A slightly raised value with otherwise normal liver values is almost always lifestyle and falls within weeks.
What does a low gamma-GT mean?
Nothing. Gamma-GT is not a deficiency, and a low value means a liver that is little burdened: little alcohol, little belly fat, no medicines the liver has to break down. That is the favourable side of the band.
What does alcohol do to gamma-GT?
Alcohol switches on the production of the enzyme in the liver cells, and in anyone who drinks regularly gamma-GT sits high while ALT can still be normal. It responds to the average of the last few weeks, not to one evening. If you stop or cut down, the value falls back to normal in four to six weeks in most people. That makes gamma-GT the value that shows what a month without delivers.
How do I lower my gamma-GT?
With the same things that relieve the liver: less alcohol, less sugar and soft drinks, less belly fat and more exercise. With alcohol a month without is the fastest test; with belly fat a few kilos off is often enough already. If you take a medicine that burdens the liver, the rise is explained by that and nothing needs doing. Have blood drawn again after six weeks to see whether it worked.
How does gamma-GT help read ALP?
ALP comes from the bile ducts and from bone, and the number alone does not say which. Gamma-GT does rise with a problem in the bile ducts and not with bone. So high ALP with a high gamma-GT is the bile ducts; high ALP with a normal gamma-GT is bone, as in growth, a fracture, a vitamin D deficiency or pregnancy.
Do I need to fast for a gamma-GT test?
No. Gamma-GT barely moves with food. What does count is what you drank in recent weeks, because that is what the enzyme responds to. Have blood drawn in an ordinary week, and the other liver values come from the same draw.
Which tests include gamma-GT?
Gamma-GT is in the Liver function test (€59, also as an add-on for €15), in the comprehensive test (€229) and in .
Related biomarkers
Read on
Sources
- 1.Unilabs, test catalogue (Dutch): GGT. 2026. bepalingenklapper.nl
- 2.Star-shl, test catalogue (Dutch): GGT. 2026. star-shl.nl
- 3.Certe, test catalogue (Dutch): GGT. 2026. bepalingenwijzer.certe.nl
- 4.Clinical Diagnostics, lab guide (Dutch): GGT. 2026. clinicaldiagnostics.nl
- 5.LESA Laboratory diagnostics (Dutch primary-care laboratory agreement). 2026. richtlijnen.nhg.org
- 6.NHG guideline on viral hepatitis and other liver disorders (M22), Dutch College of General Practitioners. 2023. richtlijnen.nhg.org
Educational information only, not medical advice. Consult a healthcare professional for clinical decisions.
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