What Is TUDCA? What It Is Used For and How It Works

TUDCA, short for tauroursodeoxycholic acid, is a hydrophilic, or water-loving, bile acid that your liver makes in small amounts. It is a prescription medicine in Italy and a dietary supplement in the US, where it is used to support healthy bile flow and the liver.

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TUDCA comes up more and more in conversations about the liver, the gallbladder and life after gallbladder removal. The name is a mouthful, and much of what is written about it online gets the basics wrong, from where it is made in the body to what it is approved for.

This guide explains what TUDCA is, how your body makes it, what supplement TUDCA is made from, what it is used for in different countries, and how it relates to ursodiol and milk thistle. For the research on each claimed benefit, see our guide to TUDCA benefits.

What Is TUDCA?

TUDCA is a bile acid, one of the detergent-like molecules in bile that aid digestion [1]. Its full name, tauroursodeoxycholic acid, describes its structure: it is ursodeoxycholic acid (UDCA) joined to taurine, an amino acid [2]. It occurs naturally in human bile and takes part in the normal circulation of bile acids between your gut and liver [3].

What sets TUDCA apart is that it is hydrophilic, or water-loving [2]. Bile contains a mix of bile acids, and TUDCA and UDCA together make up only about 2% of it [2]. Most of the rest are other bile acids, such as cholic and chenodeoxycholic acid, the two main ones your liver makes [4].

How Is TUDCA Made in the Body?

Your body makes TUDCA in three steps, shared between the liver and the bacteria in your gut. Several popular pages put the whole process in the gut, but the last step happens in the liver.

1. The liver makes bile acids from cholesterol

Your liver turns cholesterol into two main bile acids, cholic acid and chenodeoxycholic acid [4]. Before sending them into bile, it joins them to taurine or glycine, and in the body they form salts, hence the name bile salts [4].

2. Gut bacteria turn some of them into UDCA

In the intestine, bacteria change some bile acids into new forms [4]. UDCA is one of these, a so-called secondary bile acid that is made by gut bacteria [2].

3. The liver joins UDCA to taurine

Most bile acids are reabsorbed near the end of the small intestine and carried back to the liver [1]. There, UDCA can be joined to taurine, which makes TUDCA, and sent back out into bile [2].

What Is TUDCA Made From in Supplements?

TUDCA's best-known natural source is bear bile, but it can also be made in a lab. In bears, almost all of their UDCA is in the form of TUDCA. It averaged about a third of the bile acids in American black bears and under 20% in the other bears studied, while in the giant panda and related carnivores it was absent or found only in traces [5]. Bear bile was first recorded in an official Chinese medicine text in 659 AD and has been used in traditional medicine ever since [6].

Bear bile is still collected from farmed bears in parts of Asia, a practice that has drawn sustained criticism on animal welfare grounds [6, 7]. Researchers and producers have developed alternatives: TUDCA can be made by chemically joining UDCA to taurine, or by converting bile acids from chicken bile with enzymes [8]. Commercial bile acids are often made from cattle bile [9].

Dr.Primal's TUDCA is made synthetically, and no bears or bear bile are involved in making it. If you have a specific dietary need, such as avoiding animal-derived ingredients, ask any supplier what their starting materials are, because "synthetic" describes how an ingredient is made rather than what it starts from.

What Does TUDCA Do?

Taken by mouth, TUDCA is absorbed and joins the bile acids your body recycles, shifting the mix toward the water-loving kind. In people with primary biliary cholangitis taking 500 to 1,500 mg a day for six months, UDCA and its taurine and glycine forms rose to about a third to two-fifths of the bile acids in bile [10]. TUDCA was also taken apart and rebuilt as it recycled, the same way the body handles its own bile acids [10].

Bile acids act as detergents that aid digestion [1], and TUDCA adds more of the water-loving kind to the mix. That shift in the makeup of bile is the reasoning behind using TUDCA to support healthy bile flow and the liver. In people with gallstones, for example, TUDCA made bile less saturated with cholesterol [11].

In laboratories, TUDCA is also studied as a chemical chaperone, a molecule that helps cells cope with stress from misfolded proteins inside the endoplasmic reticulum, the part of the cell that folds new proteins [12]. Most of that research is in cells and animals [2], and in the one placebo-controlled trial that measured those stress markers in people, they did not change in four weeks [13]. Our article on TUDCA as a chemical chaperone explains it.

What Is TUDCA Used For?

What TUDCA is used for depends on the country. It is a medicine in some places, a supplement in others, and was briefly part of a US prescription drug.

As a medicine in Italy and Turkey

In Italy, TUDCA has been a licensed prescription medicine since 1991 for cholesterol gallstone problems, including bile duct stones after biliary surgery [3, 14]. Turkey's label also lists liver conditions in which bile flow is reduced and "biliary dyspepsia with or without cholecystectomy", meaning indigestion linked to bile, with or without gallbladder removal [15].

As a dietary supplement in the US

In the US, TUDCA is sold as a dietary supplement. The FDA does not approve dietary supplements before they go on sale, and companies are responsible for making sure their products are safe and their labels truthful [16, 17]. As a supplement, TUDCA is used to support healthy bile flow, fat digestion and the liver.

In a withdrawn US drug for ALS

Taurursodiol, another name for TUDCA, was one of two ingredients in a prescription drug for ALS approved in the US in 2022 [18]. After a larger trial did not meet its goals, the company took it off the market in 2024, and the FDA formally withdrew its approval in 2025 [19, 20]. A separate large trial of TUDCA alone in ALS also fell short [21]. There is currently no FDA-approved drug containing TUDCA.

In research

In studies of people, TUDCA has been tested mainly in liver conditions, gallstones, insulin sensitivity and indigestion after gallbladder removal [22, 23, 13, 24]. Our review of the human research appraises 27 published studies in digestive and liver health.

Does TUDCA Dissolve Gallstones?

TUDCA is licensed for gallstone problems in Italy, but TUDCA supplements are not a gallstone treatment, and no one should rely on one to dissolve stones. In the only randomized comparison that measured stone dissolution, UDCA dissolved stones completely more often than TUDCA [23]. Several popular pages lead with dissolving gallstones, which overstates the evidence.

If you have gallstones, the options range from watching and waiting to surgery or a prescription bile acid. Our guide to gallbladder sludge covers related questions.

Is TUDCA the Same as UDCA (Ursodiol)?

TUDCA and UDCA are closely related but not the same, and one is not a stand-in for the other. TUDCA is UDCA with taurine attached [2]. In the body the two convert back and forth, which is why taking TUDCA raises UDCA in bile [10].

In the US, UDCA is a prescription medicine called ursodiol. It is a long-established medicine, first approved by the FDA in 1987 [25]. Doctors prescribe it for some gallstones, to help prevent gallstones during rapid weight loss, and for a chronic bile duct disease called primary biliary cholangitis [26, 25]. Being offered it is common and simply means your doctor has a well-tested option in mind.

	TUDCA	UDCA (ursodiol)
What it is	UDCA joined to taurine	The bile acid itself, made as a medicine
Status in the US	Dietary supplement	Prescription medicine since 1987
Main uses	Supporting healthy bile flow and the liver	Some gallstones, gallstone prevention during rapid weight loss, primary biliary cholangitis
Head-to-head results	Similar on the main liver test in the largest primary biliary cholangitis trial, though two other liver enzymes fell more on UDCA; UDCA dissolved gallstones more often

If you have been prescribed ursodiol, keep taking it as directed and talk to your doctor before adding or switching to TUDCA. Our review of TUDCA vs UDCA compares every head-to-head study [27, 23].

Is Milk Thistle the Same as TUDCA?

No. Milk thistle is a plant extract, while TUDCA is a bile acid your own body makes. They are often sold side by side as liver supplements, but they are different substances studied for different reasons [28]. Our comparison of TUDCA vs milk thistle goes through both.

Where Does TUDCA Fit Without a Gallbladder?

After gallbladder removal, your liver keeps making bile [29], but it flows directly into the small intestine instead of being stored for meals [30]. Shortly after a fat-rich meal, people without a gallbladder have far less bile acid on hand than people with one [31].

That is where TUDCA comes in. Dr.Primal's TUDCA is made for life after gallbladder removal and taken with meals, when your body calls on bile the most, to support healthy bile flow and fat digestion. One study after gallbladder removal found indigestion eased faster on TUDCA in the first month, after which the untreated group caught up [24]. Our guide to TUDCA after gallbladder removal covers it in detail.

Who Should Not Take TUDCA?

The Italian medicine label lists the situations in which TUDCA should not be taken [3]:

• pregnancy or breastfeeding
• an active peptic (stomach) ulcer
• frequent gallbladder attacks, or acute inflammation or blockage of the gallbladder or bile ducts
• after surgery that removed part of the lower small intestine (the ileum)

The same label advises keeping it two hours apart from bile acid binders and aluminum antacids [3]. If you take prescription medicines or have kidney or liver disease, ask your doctor or pharmacist before starting it.

In Summary: What TUDCA Is

TUDCA is a water-loving bile acid your body makes in small amounts, built in the liver from UDCA that gut bacteria produce. It is a prescription medicine for gallstone problems in Italy and a dietary supplement in the US, and it is related to, but not the same as, the prescription drug ursodiol.

If you are trying to work out whether bile is behind your own digestive symptoms, our digestion quiz is a quick way to put your symptoms and habits in order.

This article is for general education and is not a substitute for advice from your doctor. TUDCA is sold as a dietary supplement. These statements have not been evaluated by the Food and Drug Administration. This product is not intended to diagnose, treat, cure, or prevent any disease.