You saw one flagged number on a blood panel and went looking for a way to bring it down. That is usually how people arrive at TUDCA and UDCA.
This article starts from a study that changes the question, because it shows the number falling while the disease stays exactly where it was.
What GGT actually is
GGT (gamma-glutamyl transferase) is an enzyme. Its main job is recycling glutathione, the cell primary antioxidant.
A 2022 review in Liver International describes it in one sentence worth remembering: GGT is very sensitive and very non-specific.
In plain terms, it notices almost any irritation of the liver but tells you nothing about the cause. A high GGT is a question, not an answer.
Why clinicians take it seriously anyway
A meta-analysis of 273,141 people compared the highest quartile of GGT against the lowest.
- Cardiovascular mortality: 52% higher
- All-cause mortality: 56% higher
- The association held after accounting for alcohol intake
That is association, not causation. GGT is not killing anyone. It is marking something else that is happening, usually metabolic. And this is exactly where the mistake begins.
What pushes GGT up
| Cause | Note |
|---|---|
| Alcohol | The best known, far from the only one |
| Fat in the liver | Common and commonly missed |
| Impaired bile flow | Where GGT rises highest |
| Medicines | Anticonvulsants, some antibiotics and others |
| Excess weight and diabetes | Tracks with metabolic risk |
| Supplements and herbals | A recognised cause of liver injury |
Notice the problem. Six different causes, one number. Lowering the number does not tell you which of the six you fixed.
UDCA: the number fell, the fat did not
This is the most important section here.
A small Brazilian trial from 2003 took 30 people with excess weight, fatty liver on ultrasound and raised enzymes. Half took UDCA for three months, half took placebo. Body weight did not change in either group.
In the UDCA group, ALT, AST and GGT all fell significantly. In the placebo group they did not.
But the researchers also ran CT scans to measure the fat itself. It had not moved. After three months the value was essentially identical to baseline.
Their own conclusion was that UDCA lowers liver enzymes, but this effect is not related to any change in liver fat content.
Translation: you fixed the thermometer, not the room.
TUDCA versus UDCA
TUDCA is the same bile acid conjugated with taurine. There is exactly one head-to-head comparison of the two in humans.
Twenty-three patients with primary biliary cholangitis took both, each at 500 mg daily for six months, with a three-month washout in between. Cholestasis-related enzymes, GGT among them, improved on both.
No significant difference between them was found. The conclusion was that in the short term TUDCA appears safe and at least as effective as UDCA.
Two honest caveats. Twenty-three people is small. More importantly, these were patients with an autoimmune bile-duct disease. If your GGT is up because of fat and body weight, that is not your condition.
The distinction that matters
UDCA is a medicine. It is prescribed, it has approved indications, and a clinician decides when it is appropriate.
TUDCA is sold as a food supplement. That makes it neither better nor worse. It makes it unregulated in a way the other is not.
We sell supplements and we will still say it plainly: if your GGT is high, the first step is not to order something. The first step is to find out which of the six causes is yours.
What to do about a high GGT
- Do not panic over a single result. GGT moves for many reasons, some of them temporary. A clinician decides whether to repeat it.
- Declare everything you take. Supplements and herbals included. They are a recognised cause of liver injury.
- Read GGT alongside the rest. ALT, AST and alkaline phosphatase together point in a direction; GGT alone does not.
- Treat the cause. Where the cause is fatty liver, that means food and body weight, which change the tissue and not merely the number.
Frequently asked questions
Will TUDCA lower my GGT?
In people with cholestatic disease, enzymes improved. In metabolic fatty liver there is no such trial. And a falling number was never the goal.
Then why does everyone talk about lowering enzymes?
Because enzymes are easy to measure. One number before and one after looks like proof. The Brazilian trial shows precisely why it is not: the enzymes fell and the fat stayed.
How high is worrying?
It depends on the laboratory reference range, on sex, and on your other results. There is no single universal number. That judgement belongs to your clinician.
I only drink a little. Is that the cause?
It might be. But in the meta-analysis the link between high GGT and mortality persisted after accounting for alcohol. “It is just the drinking” is not the automatic answer.
What if GGT is high but ALT and AST are normal?
That pattern is common and usually points toward the bile ducts, medicines or alcohol rather than injury to the liver cells themselves. It still needs proper assessment.
Can supplements themselves raise GGT?
Yes. Herbal and dietary supplements are a recognised cause of liver injury. If you started something new before the test, say so.
References
- Brennan, P. N., Dillon, J. F., & Tapper, E. B. (2022). Gamma-glutamyl transferase (γ-GT) – an old dog with new tricks? Liver International, 42(1), 9-15. PMID: 34775657
- Du, G., Song, Z., & Zhang, Q. (2013). Gamma-glutamyltransferase is associated with cardiovascular and all-cause mortality: a meta-analysis of prospective cohort studies. Preventive Medicine, 57(1), 31-37. PMID: 23571185
- Santos, V. N., Lanzoni, V. P., Szejnfeld, J., Shigueoka, D., & Parise, E. R. (2003). A randomized double-blind study of the short-time treatment of obese patients with nonalcoholic fatty liver disease with ursodeoxycholic acid. Brazilian Journal of Medical and Biological Research, 36(6), 723-729. PMID: 12792701
- Larghi, A., Crosignani, A., Battezzati, P. M., et al. (1997). Ursodeoxycholic and tauro-ursodeoxycholic acids for the treatment of primary biliary cirrhosis: a pilot crossover study. Alimentary Pharmacology & Therapeutics, 11(2), 409-414. PMID: 9146783
- Navarro, V. J., Barnhart, H., Bonkovsky, H. L., et al. (2014). Liver injury from herbals and dietary supplements in the U.S. Drug-Induced Liver Injury Network. Hepatology, 60(4), 1399-1408. PMID: 25043597
