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Science · Evidence review

TUDCA vs UDCA

What has been shown for UDCA, the prescription bile acid, what has been shown for TUDCA itself, and where common TUDCA claims get their evidence.

Read the review
Science

Evidence review

Two closely related bile acids, one a prescription medicine and one a supplement in the US. Here is the research on each, and on the two compared.

Written by
Dr.Primal Editorial
Fact-checked
Against primary sources
Evidence searched
October 20, 2026
Version
1.0
Contents
  1. Two forms of one bile acid
  2. Where each one stands
  3. What has been shown for UDCA
  4. TUDCA and UDCA, head to head
  5. Common claims, and where their evidence comes from
  6. What we still don't know
  7. All 44 studies
  8. How we did this review
  9. About this review

The short version

  1. TUDCA is UDCA with the amino acid taurine attached. In the body each partly turns into the other, so the two share a pathway.[1,2,3]
  2. UDCA (ursodiol) is a prescription medicine with a large body of research. It has been approved in the US since 1987. It is the first treatment for primary biliary cholangitis, and pooled trials show it dissolves cholesterol gallstones completely in about a third of people treated, and prevents new ones during rapid weight loss.[4,5,6,7]
  3. We found ten studies that compared the two directly. In the largest randomized trial, 199 people with primary biliary cholangitis, the main liver test result was similar. UDCA did better in two small trials from 1993, and in one absorption study the bile carried a little more UDCA on TUDCA than on UDCA itself.[8,9,10,11]
  4. In two conditions, UDCA trials found no benefit, or harm at high doses. In fatty liver, biopsies on UDCA were similar to placebo, and in primary sclerosing cholangitis high doses were linked to more serious outcomes.[12,13]
  5. Bile flow and fat digestion, two of the claims we saw most often for TUDCA, have been studied with UDCA; we found no TUDCA study in people that measured them. For TUDCA, protection of liver cells from toxins and medicines has been studied in cells and animals, not in people.
  6. A UDCA result describes UDCA. For TUDCA, the direct evidence is the TUDCA studies themselves, which we set out in our review of them.

Evidence at a glance

UDCA and TUDCA, use by use

  • 10studies we found that compared TUDCA with UDCA in people
  • 199people in the largest randomized trial
  • 3uses for which UDCA is approved in the US
  • 0studies we found in people of TUDCA that measured bile flow or fat digestion

What the studies found, and how much research stands behind it, for each

The research grade measures how much evidence there is and how firm it is. A low grade means a finding is not yet confirmed.

  • Primary biliary cholangitis
    UDCAFound: Better liver tests and slower progression; longer transplant-free survival in a pooled analysis of three trials and a large cohort, though not in a Cochrane review of all trialsResearch: StrongRandomized trials of 146 to 222 people, pooled analyses and a cohort of 3,902
    TUDCAFound: Similar to UDCA on the main measure in the largest trial; UDCA did better on some liver tests, and in one small trialResearch: ModerateOne 24-week trial of 199 people, plus smaller ones; laboratory results
  • Dissolving cholesterol gallstones
    UDCAFound: Complete dissolution in about 37% of people with non-calcified stones, more often in small ones; stones often returnResearch: StrongA pooled analysis of 23 randomized trials; dissolution on imaging, and pain before surgery not reduced in one trial
    TUDCAFound: Less cholesterol in bile; UDCA dissolved stones more often in a head-to-head trialResearch: EarlySmall trials; a licensed use in Italy and Turkey
  • Preventing gallstones during rapid weight loss
    UDCAFound: Fewer gallstones on ultrasound, and fewer causing symptoms in a pooled analysisResearch: StrongA pooled analysis of 14 randomized trials and 3,619 people
    TUDCAFound: Not yet testedResearch: Not yet studiedNo published study in people
  • After gallbladder removal
    UDCAFound: Less pain in 12 people with crystals in their bile; less indigestion in one older trialResearch: EarlySeveral small controlled trials, each on a different outcome; fewer duct stones returned on UDCA in two of them, not a significant difference
    TUDCAFound: Faster relief of indigestion in the first monthResearch: PreliminaryOne study of 203 people, without a placebo
  • Cholestasis of pregnancy
    UDCAFound: Itch slightly lower; the baby's outcomes similar to placebo in the largest trialResearch: ModerateOne trial of 605 women and pooled data on 6,974
    TUDCAFound: Not yet testedResearch: Not yet studiedNo published study in people
  • Fatty liver (NASH)
    UDCAFound: Biopsy findings similar to placebo; ALT lower at high dosesResearch: ModerateThree randomized trials of 126 to 185 people
    TUDCAFound: Not yet tested as a treatmentResearch: Not yet studiedNo published study in people has tested TUDCA as a treatment; liver fat unchanged in one 4-week study
  • Primary sclerosing cholangitis
    UDCAFound: Liver tests improve; at high doses, serious outcomes were more commonResearch: ModerateRandomized trials of 105 to 219 people
    TUDCAFound: Not yet testedResearch: Not yet studiedNo published study in people
  • Strong
  • Moderate
  • Early
  • Preliminary
  • Not yet studied

Research grades are ours, made on the scale described in “How we did this review”. TUDCA grades are carried over from our review of the TUDCA studies. Sources: [4,5,8,9,10,12,13,14,15,16,17,18,19,20,21,22,23,24,25,26,27,28,29,30,31,32]

Two forms of one bile acid

UDCA (ursodeoxycholic acid) is a bile acid that gut bacteria make from one of the main bile acids the liver produces. After it is absorbed, the liver attaches an amino acid to it: mostly glycine, and a smaller share taurine. The taurine form is TUDCA (tauroursodeoxycholic acid).[33] Together they make up a small share of the body's bile acids, about 2%.[34]

The two keep changing into each other. After a dose of TUDCA, much of what appears in the blood is UDCA.[35] As bile acids recycle between the gut and the liver, they lose their amino acid and gain one again, so TUDCA taken by mouth raises UDCA and its conjugates in bile.[3,11] What gets attached depends on what was taken:

In the body

What the UDCA in bile is linked to depends on which one was taken

After TUDCA, people with blocked bile ducts (Rudolph 2002)[1]

  • Taurine-linked95.4%

After UDCA, the same people

  • Glycine-linked79.8%

Share of the UDCA in bile that was linked to taurine (after TUDCA) or to glycine (after UDCA). Eight people with bile duct blockage and drains placed through the skin; the two treatments were taken in turn.

They also differ in small ways. TUDCA is more water-loving, and in one study it was broken down less into lithocholic acid, a more toxic bile acid that gut bacteria make.[8,11]

Editorial note

Because TUDCA becomes UDCA in the body, it is sometimes said that UDCA's trial results apply to TUDCA. Here is how we read the evidence on that.

The conversion studies show that the two share a pathway. Whether they give the same results is a separate question, and only trials that test both can answer it. Those trials found similar results on some measures and different results on others. Some of UDCA's established uses, such as preventing gallstones during rapid weight loss, have not yet been tested with TUDCA.

So in this review a UDCA result is reported as a UDCA result, and a TUDCA result as a TUDCA result. Dr.Primal sells TUDCA, so we would rather draw that line plainly than let one stand in for the other.

Dr.Primal Editorial.

Where each one stands

UDCA · United States

Prescription medicine since 1987

Sold as ursodiol. Approved for dissolving gallstones and preventing them during rapid weight loss, and since 1997 for primary biliary cholangitis.[7,36,37]

TUDCA · Italy and Turkey

Licensed medicine

Prescription-only in Italy since 1991, for cholesterol gallstones. Licensed in Turkey since 2007, where the label adds chronic cholestatic liver disease and indigestion linked to bile, with or without a gallbladder.[25,26,38]

TUDCA · United States

Dietary supplement

Sold as a supplement. As taurursodiol, it was part of Relyvrio, an ALS drug approved in 2022 and withdrawn in 2025.[39]

A trial registration says TUDCA is also approved in China for cholesterol gallstones; we could not confirm this with China's regulator.[40]

The US and European liver societies both name UDCA, at 13–15 mg per kg a day, as the first treatment for primary biliary cholangitis.[6,41]

What has been shown for UDCA

UDCA has been tested in randomized trials in several liver and bile conditions. This section sets out the main trials, pooled analyses and guidelines for each use. For every study we use the same appraisal fields; the full list is in the evidence table.

Primary biliary cholangitis

Primary biliary cholangitis (PBC) is a long-term autoimmune disease of the small bile ducts in the liver. In placebo-controlled trials of 146 to 222 people over two years, UDCA lowered bilirubin and other liver tests, improved biopsy findings and delayed treatment failure.[42,43,44] When three of those trials were pooled, 548 people in all, survival without a liver transplant was longer on UDCA, mainly in people with moderate or advanced disease.[16]

The longest view comes from people followed for years outside trials:

UDCA in primary biliary cholangitis

Survival without a liver transplant, treated and untreated

5 years

  • Treated with UDCA90%
  • Untreated79%

10 years

  • Treated with UDCA78%
  • Untreated59%

15 years

  • Treated with UDCA66%
  • Untreated32%

An international analysis of 4,845 patients, as reported in the US and European guidelines. Observational data: treatment was not assigned at random.[6,41]

Harms 2019

UDCA: primary biliary cholangitis · appraisal
People
3,902 people with primary biliary cholangitis in 8 countries (Global PBC Study Group)
Design
Cohort study, statistically weighted
Compared with
Untreated patients
Randomized
No
Blinded
No
Dose
Not stated
Length
Median 7.8 years
Measured
Liver transplant or death
Result
10-year transplant-free survival 79.7% treated vs 60.7% untreated; hazard ratio 0.46 (95% CI 0.40–0.52), at every disease stage.
Main limits
Observational: treatment was not assigned at random.

Source: [15] Harms MH, van Buuren HR, Corpechot C, et al. Ursodeoxycholic acid therapy and liver transplant-free survival in patients with primary biliary cholangitis. J Hepatol. 2019;71(2):357-365.

A Cochrane review of 16 trials (1,447 people) found no significant effect on death or transplant. Its trials ran for a median of two years, and 15 of the 16 were judged at high risk of bias.[14] The US guidance notes that such reviews often include short trials and doses now known to be too low.[6]

Dissolving gallstones

In the US, UDCA is approved for gallbladder stones that do not show on X-ray, are not calcified and are smaller than 20 mm, in people for whom surgery is risky or who prefer not to have it.[36] A pooled analysis of 23 randomized trials found complete dissolution in 37.3% of people on at least 7 mg per kg a day for more than six months; stones under 10 mm dissolved more often.[4] Stones often come back: in 25–64% of people within five years, according to European guidance.[45] In 177 people waiting for gallbladder surgery, UDCA did not change how many stayed free of gallstone pain.[17]

Preventing gallstones during rapid weight loss

Fast weight loss, from a very-low-calorie diet or weight-loss surgery, raises the chance of forming gallstones. Preventing them is an approved use of UDCA in the US, and European guidance calls it the standard preventive treatment.[36,45]

UDCA during rapid weight loss

People who developed gallstones

Weight-loss diet, 16 weeks (Shiffman 1995)[46]

  • UDCA 600 mg a day3%
  • Placebo28%

After gastric bypass, 6 months (Sugerman 1995)[47]

  • UDCA 600 mg a day2%
  • Placebo32%

After gastric banding, 12 months (Miller 2003)[48]

  • UDCA 500 mg a day3%
  • Placebo22%

14 trials pooled, 3,619 people (Sharma 2023)[5]

  • UDCA8.3%
  • Control38.1%

Gallstones seen on ultrasound, whether or not they caused symptoms. In the largest single trial (985 people), gallstones causing symptoms were 6.5% on UDCA and 9.7% on placebo, short of statistical significance.[49]

In the largest trial, UPGRADE, the overall result for gallstones that caused symptoms fell short of significance. Among people who had no gallstones before their surgery, the risk was about half on UDCA.[49]

After gallbladder removal

Five studies have tested UDCA after the gallbladder or bile duct stones were removed. In 12 people with ongoing pain and crystals in their bile, pain improved or went away on UDCA and not in the untreated group.[28] An older Italian trial reported less indigestion but no change in pain.[29] In two trials in people whose bile duct stones had been removed, some of whom still had a gallbladder, stones came back less often on UDCA (1 of 22 vs 4 of 24, and 6.6% vs 18.6%), but neither difference was statistically significant. European endoscopy guidance suggests against using UDCA for this.[30,31,50] A study of bile reflux into the stomach after surgery had no comparison group.[51]

Cholestasis of pregnancy

In intrahepatic cholestasis of pregnancy, bile acids build up in the mother's blood and cause intense itching. In the largest trial, PITCHES, 605 women took UDCA or placebo until birth. The combined outcome for the babies was similar in both groups, and itch was 5.7 mm lower on a 100 mm scale.[18] A pooled analysis of individual records from 6,974 women found stillbirth or preterm birth was lower on UDCA in the randomized trials, though not across all studies.[19] US maternal-fetal medicine guidance recommends UDCA as the first treatment for the mother's symptoms.[52]

Fatty liver and primary sclerosing cholangitis

In fatty liver inflammation (NASH), two randomized trials, one at standard and one at high doses, found biopsy findings similar to placebo. A third, at higher doses still, lowered ALT but did not repeat the liver biopsy.[12,20,21] US guidance says UDCA should not be used as a treatment for NASH.[53]

In primary sclerosing cholangitis, a long-term disease of the bile ducts inside and outside the liver, UDCA improved liver tests but did not change clinical outcomes, at standard doses and at somewhat higher ones.[22,23] At 28–30 mg per kg a day, a trial of 150 people was stopped early: serious outcomes were more common on UDCA, and in people who also had ulcerative colitis, so were precancerous changes or cancer in the bowel.[13,54] US guidance allows a lower dose to be considered and says high doses should not be prescribed.[55]

Side effects of UDCA

In the US gallstone trials, side effects on UDCA were mostly about as common as on placebo. Diarrhea was reported by 27.1% on UDCA and 21.4% on placebo in the dissolution trials.[36] A systematic review lists diarrhea, rare skin reactions, and reduced absorption when taken with bile acid binders or aluminum-containing antacids.[56]

TUDCA and UDCA, head to head

We found ten studies in people that gave TUDCA and UDCA side by side, all from 1984 to 2016. We found none published since.

Head to head

Every study that compared TUDCA with UDCA directly

  • Gallo 1993[10]Gallstones · Dissolution, symptoms, tolerabilityResult: UDCA better
  • Ferri 1993[9]Primary biliary cholangitis · Liver tests, tolerabilityResult: UDCA better
  • Ma 2016[8]Primary biliary cholangitis · Main measure, ALP response (199 people)Result: no clear difference
  • Larghi 1997[57]Primary biliary cholangitis · Liver enzymesResult: no clear difference
  • Bazzoli 1995[58]Gallstones (not randomized) · Stones calcifyingResult: no clear difference
  • Portincasa 1996[59]Gallstones and healthy volunteers · Gallbladder emptyingResult: no clear difference
  • Hardison 1984[60]Healthy men · Bile acid production, cholesterol absorptionResult: no clear difference
  • Rudolph 2002[1]Blocked bile ducts · AbsorptionResult: no clear difference
  • Invernizzi 1999[11]Primary biliary cholangitis · AbsorptionResult: TUDCA better
  • Pan 2013[61]Cirrhosis · Liver tests (no comparison reported)Result: not compared

Each mark shows the study's main comparison. In Ma 2016, two secondary liver tests fell more on UDCA and symptoms improved more on TUDCA. A hollow mark means the study did not compare the two groups.

The largest randomized trial is Ma 2016:

Ma 2016

TUDCA and UDCA compared · appraisal
People
199 people with primary biliary cholangitis (129 TUDCA, 70 UDCA)
Design
Randomized, double-blind, non-inferiority
Compared with
UDCA
Randomized
Yes (2:1)
Blinded
Double-blind, double-dummy
Dose
750 mg/day, both
Length
24 weeks
Measured
Share whose ALP fell by more than 25%
Result
75.97% on TUDCA vs 80.88% on UDCA (P=0.453). ALT and GGT fell more on UDCA (P=0.029, 0.027). Of the symptoms and signs present at the start, 48.57% improved on TUDCA vs 25.58% on UDCA (P=0.035); itching rose on UDCA only. Side effects 44% vs 40%, none serious.
Main limits
24 weeks; a laboratory endpoint; 2:1 allocation; no confidence interval reported for the 10% margin; partly sponsored by a commercial company.

Source: [8] Ma H, Zeng M, Han Y, et al. A multicenter, randomized, double-blind trial comparing the efficacy and safety of TUDCA and UDCA in Chinese patients with primary biliary cholangitis. Medicine (Baltimore). 2016;95(47):e5391.

In primary biliary cholangitis, one 1993 trial of 30 people found UDCA better on liver tests and better tolerated, while a crossover trial of 23 people found no difference in liver enzymes.[9,57] In gallstones, UDCA dissolved stones completely more often in a trial of 31 people, and stones calcified at similar rates in a larger comparison that was not randomized.[10,58] Gallbladder emptying and the body's own bile acid production were unchanged on either.[59,60] A small trial in cirrhosis reported changes within each group but did not compare them.[61]

A Cochrane review of treatments for primary biliary cholangitis included two of these trials and found the evidence for every treatment, UDCA included, of low or very low certainty.[62]

Absorption

Two crossover studies measured how much of each reached the bile:

Absorption

How much of the bile was UDCA or its conjugates, on each

750 mg of each, 12 women with PBC (Invernizzi 1999)[11]

  • TUDCA32.6%
  • UDCA29.2%

Equal molar doses, 8 people with bile drains (Rudolph 2002)[1]

  • TUDCA54.6%
  • UDCA55.2%

The first difference was statistically significant; the second was not. Both studies were in people with liver or bile-duct disease.

One more head-to-head trial, in liver disease in cystic fibrosis, is listed as completed in 2001; we found no published results.[63]

Common claims, and where their evidence comes from

We read 14 pages from 11 supplement sellers and health sites and grouped what they say about TUDCA in digestive and liver health into claims. The table shows the 13 we saw on more than one site. For each, the table shows the studies in people with TUDCA, the studies in people with UDCA, and whether the rest of the support comes from lab and animal research.

Where the evidence comes from

Common TUDCA claims, and the studies behind each

ClaimSeen onTUDCA, in peopleUDCA, in peopleLab and animal only
Bile flow8 of 11No study found that measured itBile volume was higher on UDCA in the first 10 days after a liver transplant (33 people)[64]Rats[65]
Protecting liver cells from damage7 of 11No study in people has tested protection from toxins or medicines. In 52 infants on intravenous nutrition, liver tests did not differ from no treatment[66]A trend toward lower liver enzymes during chemotherapy in 39 children, in a pilot study[67]Rat liver cells; mice after an acetaminophen overdose[68,69]
Fat digestion and fat-soluble vitamins7 of 11No study found that measured itTwo studies with opposite results: less fat in stool in 10 people with cirrhosis, lower fat absorption in 15 healthy people[70,71]Mice: less fat transport and fatty acid absorption in the gut[72,73]
Fatty liver4 of 11Liver fat unchanged after 4 weeks in 20 adults with obesity; no study as a treatment[32]Biopsy findings similar to placebo in two trials; ALT lower at high doses[12,20,21]Mice[72,73]
Liver detox or cleansing4 of 11No study defines or measures itNo study defines or measures it—
Cell stress (ER stress)4 of 11Colon-lining stress markers fell in 14 people with ulcerative colitis, without a control group, in a study not yet peer reviewed; muscle and fat markers unchanged in 20 adults[32,74]Liver stress markers rose on UDCA in 40 people before bariatric surgery[75]Obese mice[76]
Gut lining and gut bacteria4 of 11The ulcerative colitis study above, and one case report; no study measured gut permeability[74,77]—Mice with colitis[78]
After gallbladder removal4 of 11Indigestion eased faster in the first month in 203 people, without a placebo[27]Less pain in 12 people with crystals in their bile[28]—
Clearing excess cholesterol4 of 11Blood cholesterol fell at the two higher doses in 24 people with PBC; cholesterol absorption fell in 6 healthy men[60,79]Blood cholesterol fell in a 146-person PBC trial[42]—
Liver enzymes3 of 11Lower than placebo in 150 people with hepatitis C. In PBC, similar to UDCA on the main measure in the largest trial, where ALT and GGT fell more on UDCA. No difference from no treatment in infants on intravenous nutrition, or when added to interferon in hepatitis C[8,66,80,81]Lower in many trials in PBC, and in trials in sclerosing cholangitis and fatty liver[14,21,22]—
Insulin sensitivity of the liver3 of 11Rose about 30% on TUDCA and not on placebo over 4 weeks, in 20 adults with obesity[32]Markers of blood sugar control improved at high doses in 126 people with NASH[21]Obese mice[76]
Dissolving or preventing gallstones2 of 11Bile less saturated with cholesterol in 33 people, without a control group; UDCA dissolved stones more often in a head-to-head trial[10,24]Pooled randomized trials, for dissolving and for preventing stones[4,5]Mice on a gallstone-forming diet[82]
Gallbladder emptying2 of 11Emptying unchanged after a dose and after a month[59]Emptying unchanged in the same study—

“Seen on” counts the 11 supplement sellers and health sites whose pages we read on October 20, 2026; we do not name them. Lab and animal studies are named, not appraised.

The three claims we saw most often were bile flow, protecting liver cells and fat digestion. For bile flow and fat digestion, the studies in people are UDCA studies. Protection from toxins and medicines, including acetaminophen, comes from studies in cells and animals. One page described hospital use of TUDCA for acetaminophen overdose; the source it cited was a study in mice, and we found no study of this use in people.[69]

Some claims do have TUDCA studies in people, and the table gives their results as they were: lower liver enzymes than placebo in hepatitis C, better insulin sensitivity of the liver over four weeks, and faster relief of indigestion in the first month after gallbladder removal.[27,32,80]

What we still don't know

  • Whether TUDCA prevents gallstones during rapid weight loss, as UDCA does. No trial has tested it.
  • How TUDCA affects bile flow and fat digestion in people.
  • Whether TUDCA's small differences in absorption and breakdown change outcomes that people notice, over months or years rather than weeks.
  • How TUDCA and UDCA compare in people without a gallbladder. No head-to-head study looked at this group.
  • What the head-to-head trial in cystic fibrosis found; we could not find its results.[63]

All 44 studies

Every study in people appraised in this review, on the same fields. “Not stated” means the published summary does not say, not that the answer is no. Studies of TUDCA alone are appraised in our review of the TUDCA evidence. On a phone, scroll the table sideways.

Evidence table

44 studies in people, appraised on the same fields

StudyPeopleDesignCompared withRandomizedBlindedDoseLengthMeasuredResultMain limits
TUDCA and UDCA compared
Hardison 1984[60]6 healthy menEach bile acid for a month, then a month offUDCA; time off treatmentNot statedNot statedTUDCA 20 mg/kg/day; UDCA 15 mg/kg/day1 month on eachBile acid production, cholesterol absorptionNeither changed the body's own bile acid production; cholesterol absorption fell on both.Six men; doses differ; no numbers or between-drug statistics in the abstract.
Ferri 1993[9]30 people with primary biliary cholangitis (25 finished)Randomized trialUDCAYesNot stated12–15 mg/kg/day, both6 monthsLiver tests, tolerabilityUDCA improved liver tests more (significantly for GGT) and was better tolerated. A Cochrane review counted side effects in 60% on TUDCA vs 7% (1 of 15) on UDCA.Small; article in Italian, no numbers in the English abstract.
Gallo 1993[10]34 people with gallstones (31 finished)Randomized trialUDCAYesSingle-blind10 mg/kg/day, both6 monthsStone dissolution, symptoms, tolerabilityComplete dissolution was more frequent on UDCA; UDCA eased indigestion more (p<0.01) and was better tolerated. The authors called TUDCA acceptable.Small; dissolution counts not given in the abstract.
Bazzoli 1995[58]262 people on stone-dissolving bile acids: 31 on TUDCA, 106 on UDCA, 125 on CDCAObservational comparisonUDCA, CDCANoNot statedNot statedNot statedStones becoming calcified during treatment12.9% on TUDCA, 13.2% on UDCA, 8.8% on CDCA; no significant difference.Not randomized; small TUDCA group; dose and dissolution not reported.
Portincasa 1996[59]People with gallstones and healthy volunteers (number not stated)Single dose, then 1 monthUDCA; placebo (single dose)Indexed as randomized; method not describedNot stated10 mg/kg, bothSingle dose; 1 monthGallbladder emptying on ultrasoundNeither changed emptying after a meal; the resting gallbladder was larger after a month on either.No numbers or between-drug test in the abstract.
Larghi 1997[57]23 people with primary biliary cholangitisCrossover (everyone took both)UDCAYes (order)Not stated500 mg/day, both6 months on eachLiver enzymesLiver enzymes improved on both, with no significant difference between them; no side effects reported.Small pilot; no values in the abstract; excluded by the Cochrane review because results before crossover were not given.
Invernizzi 1999[11]12 women with primary biliary cholangitisCrossoverUDCAYesNot stated750 mg/day, both2 months on eachAbsorption and breakdown of bile acidsUDCA and its conjugates made up 32.6% of bile acids in bile on TUDCA vs 29.2% on UDCA (P<.05); less lithocholic acid on TUDCA.Twelve people with liver disease; bile chemistry, not symptoms or liver outcomes.
Rudolph 2002[1]8 people with blocked bile ducts from pancreatic cancer, with drainsCrossoverUDCA at an equal molar doseYes (order)Not statedTUDCA 1,000 mg; UDCA 750 mgShort study periodsAbsorption; bile acids in bile64.6% of TUDCA vs 55.1% of UDCA absorbed, and UDCA reached 54.6% vs 55.2% of bile acids in bile; neither difference significant.Eight people with bile duct blockage from pancreatic cancer and drains through the skin, an unusual setting.
Pan 2013[61]23 people with cirrhosis (18 analyzed)Randomized, double-blindUDCAYesDouble-blind750 mg/day, both6 monthsLiver tests, fibrosis markersLiver tests improved from the start in both groups; fibrosis markers unchanged. No comparison between the groups was reported.Very small; 5 of 23 not analyzed; cause of cirrhosis not stated.
Ma 2016[8]199 people with primary biliary cholangitis (129 TUDCA, 70 UDCA)Randomized, double-blind, non-inferiorityUDCAYes (2:1)Double-blind, double-dummy750 mg/day, both24 weeksShare whose ALP fell by more than 25%75.97% on TUDCA vs 80.88% on UDCA (P=0.453). ALT and GGT fell more on UDCA (P=0.029, 0.027). Of the symptoms and signs present at the start, 48.57% improved on TUDCA vs 25.58% on UDCA (P=0.035); itching rose on UDCA only. Side effects 44% vs 40%, none serious.24 weeks; a laboratory endpoint; 2:1 allocation; no confidence interval reported for the 10% margin; partly sponsored by a commercial company.
UDCA: primary biliary cholangitis
Poupon 1991[42]146 people with primary biliary cirrhosisRandomized, double-blind, multicenterPlaceboYesDouble-blind13–15 mg/kg/day2 yearsTreatment failure (bilirubin doubling, severe complications or adverse reaction)Treatment failed in 6 on UDCA vs 13 on placebo (P<0.01). Liver tests and the average biopsy score improved on UDCA only.Two years; a composite endpoint that includes a laboratory item; survival not an endpoint.
Lindor 1994[43]180 people with primary biliary cirrhosisRandomized, double-blindPlaceboYesDouble-blind13–15 mg/kg/day2 yearsTime to treatment failureTreatment failure was delayed on UDCA (P=0.0003). Death or transplant: 7 on UDCA vs 12 on placebo (P=0.18).The composite endpoint includes withdrawal and laboratory items.
Heathcote 1994[44]222 people with primary biliary cirrhosisRandomized, double-blind, multicenterPlaceboYesDouble-blind14 mg/kg/day24 monthsChange in bilirubinBilirubin, ALP, liver enzymes, cholesterol and IgM fell on UDCA. Symptoms did not improve; deaths and transplants did not differ.A laboratory primary endpoint; the authors say a larger trial is needed to assess survival.
Poupon 1994[83]145 people from the 1991 French trial2 randomized years, then 2 years with everyone on UDCAPlacebo, then UDCAYesDouble-blind in the first phase13–15 mg/kg/day4 yearsDisease progression; transplant or deathLower risk of progression (relative risk 0.28, 95% CI 0.12–0.63) and of transplant or death (0.32, 0.14–0.74) for those first assigned UDCA.Analyzed by original assignment after the placebo group switched; transplant referral counted with transplant.
Combes 1995[84]151 people with primary biliary cirrhosisRandomized, double-blindPlaceboYesDouble-blind10–12 mg/kg once at bedtime2 yearsTreatment failureBlood tests and biopsies improved where bilirubin was below 2 at entry. Treatment failure 42% vs 60% (P=.078).A lower dose than today's standard; the abstract is truncated.
Lindor 1996[85]180 people from the 1994 Mayo trialExtended follow-up of a randomized trialPlaceboYes (original trial)Double-blind, then open13–15 mg/kg/dayTrial plus 3 yearsDeath or transplantHigher risk of death or transplant on placebo (relative risk 2.6, P=0.04).Censored when patients switched; adjusted for a risk score.
Poupon 1997[16]548 people from three randomized trials (French, Canadian, US)Combined analysis of individual patient dataPlacebo (original assignment)Yes (source trials)Double-blind in the source trialsNot statedUp to 4 yearsSurvival free of liver transplantTransplant-free survival was longer on UDCA (relative risk 1.9, 95% CI 1.3–2.8, P<0.001), mainly in people with moderate or advanced disease.Pooled by the trial authors after the fact; two trials let the placebo group switch.
Van Hoogstraten 1998[86]61 people with primary biliary cirrhosisRandomized, open dose comparisonUDCA 10 mg/kg/dayYesNo20 vs 10 mg/kg/day6 monthsLiver tests, symptoms, UDCA in bileLiver tests improved at 20 mg/kg/day; no significant change at 10. Symptoms and bilirubin did not differ.Laboratory outcomes; six months; open label.
Parés 2000[87]192 people with primary biliary cirrhosisRandomized, double-blind, multicenterPlaceboYesDouble-blind14–16 mg/kg/dayMedian 3.4 yearsDeath or transplant; complications; histologyDeath or transplant 17 vs 11, times not significantly different. UDCA lowered liver tests, improved inflammation on biopsy and slowed stage progression.More people stopped in one arm than the other.
Papatheodoridis 2002[88]86 people with primary biliary cirrhosis in GreeceRandomized, untreated controlNo treatmentYesNoNot statedMean 7–8 yearsLiver decompensation; death or transplantNo significant difference in decompensation or in liver death or transplant.Open; 14 controls switched to UDCA at their request; small.
Harms 2019[15]3,902 people with primary biliary cholangitis in 8 countries (Global PBC Study Group)Cohort study, statistically weightedUntreated patientsNoNoNot statedMedian 7.8 yearsLiver transplant or death10-year transplant-free survival 79.7% treated vs 60.7% untreated; hazard ratio 0.46 (95% CI 0.40–0.52), at every disease stage.Observational: treatment was not assigned at random.
UDCA: gallstones
Tokyo study group 1980[89]151 people with gallstones (72 analyzed)Double-blind trial, three groupsPlacebo; lower doseNot statedDouble-blind600 or 150 mg/day6–12 monthsStones dissolved or smallerDissolved or smaller in 34.5% on 600 mg, 17.4% on 150 mg, 5.0% on placebo; 83.3% for small floating non-calcified stones on 600 mg.79 of 151 dropped out or were excluded; partial response counted with dissolution.
Erlinger 1984[90]197 people with gallstonesRandomized, double-blind, dose comparisonOther UDCA doses; CDCAYesDouble-blind2.1 to 16.2 mg/kg/dayUp to 1 yearComplete dissolutionComplete dissolution in 5.9% to 28.9% by dose (28.9% at 8.4 mg/kg/day); more often in stones under 5 mm.One year; no placebo group.
Villanova 1989[91]86 people whose gallstones had dissolvedLong-term follow-upNo UDCA after dissolutionNot statedNot stated300 mg/day12 yearsStones coming backStones returned in 12.5% by year 1 and 61% by year 11. UDCA after dissolution reduced recurrence (p=0.0067), mainly in people 50 or younger.How people were allocated is not stated; one center.
Venneman 2006[17]177 people with gallstone pain waiting for surgeryRandomized, double-blindPlaceboYesDouble-blindNot statedUntil surgery (median 75 days)Staying free of biliary colicColic-free 26% on UDCA vs 33% on placebo (P=.3); pain episodes and painkiller use similar.Short treatment; not a dissolution trial.
UDCA: rapid weight loss
Broomfield 1988[92]68 people on a very-low-calorie dietRandomized, double-blind, three groupsPlacebo; aspirinYesDouble-blind1,200 mg/dayUp to 16 weeksGallstones and crystals on ultrasoundNo gallstones or crystals on UDCA; gallstones in 5 and crystals in 6 on placebo.Small; group sizes not stated in the abstract.
Shiffman 1995[46]1,004 people on a weight-loss diet, 31 centersRandomized, double-blind, three dosesPlaceboYesDouble-blind300, 600 or 1,200 mg/day16 weeksGallstones on ultrasoundGallstones in 28% on placebo vs 8%, 3% and 2% by dose. The FDA label's count of everyone enrolled gives 23% on placebo.Ultrasound finding, not symptoms.
Sugerman 1995[47]233 people after gastric bypass with a follow-up scanRandomized, double-blind, multicenterPlaceboYesDouble-blind300, 600 or 1,200 mg/day6 monthsGallstones on ultrasoundGallstones at 6 months in 32% on placebo vs 13%, 2% and 6% by dose (P<0.001 for 600 and 1,200 mg).Only people with a follow-up scan analyzed; ultrasound finding.
Miller 2003[48]152 people after gastric bandingRandomized, double-blindPlaceboYesDouble-blind500 mg/day6 months; followed 24 monthsGallstones; gallbladder removalGallstones 3% vs 22% at 12 months and 8% vs 30% at 24; gallbladder removal 4.7% vs 12%.One center; many eligible people declined.
Haal 2021 (UPGRADE)[49]985 people having bariatric surgeryRandomized, double-blind, multicenterPlaceboYesDouble-blind900 mg/day6 months; followed 24 monthsGallstones causing symptoms6.5% vs 9.7% (relative risk 0.67, 95% CI 0.43–1.04, p=0.071). In people without gallstones before surgery: 0.47 (0.27–0.84).The main result did not reach significance; the subgroup result is secondary.
UDCA: after gallbladder removal
Reggiani 1986[29]People after gallbladder removal (140 followed; trial size not stated)Follow-up study with a double-blind trialNot statedNot statedDouble-blindNot statedNot statedIndigestion and painIndigestion improved on UDCA (p=0.03); pain did not change (p=1.00).The English abstract gives no trial size, comparison, dose or length.
Swobodnik 1990[30]46 people after removal of bile duct stonesControlled trialPlaceboIndexed as randomized; method not describedNot stated500 mg/dayUp to 24 monthsBile duct stones returning; bile chemistryStones returned in 1 on UDCA vs 4 on placebo; bile cholesterol saturation fell.Small; no statistical test for recurrence; article in German.
Ozkaya 2002[51]31 people with bile reflux in the stomach after gallbladder removalBefore and after, no control groupNoneNoNoNot stated6 weeksHealing seen on endoscopyComplete healing in 9 (29%) and partial healing in the rest.No control group; symptoms not reported in the abstract.
Okoro 2008[28]12 people with pain after gallbladder removal and crystals in their bile (of 118 screened)Randomized, then controls treatedNo treatmentYesNot statedNot statedA few monthsUpper-right abdominal painPain improved or resolved on UDCA; no improvement in the untreated group (P=.01).Twelve people; one center; a narrow group.
Yamamoto 2016[31]36 people after removal of bile duct stonesRandomized, multicenterNo treatmentYesNot statedNot statedNot statedBile duct stones returning6.6% on UDCA vs 18.6% untreated (P=0.171).Very small; open control group.
UDCA: cholestasis of pregnancy
Chappell 2019 (PITCHES)[18]605 women with intrahepatic cholestasis of pregnancyRandomized, double-blind, multicenterPlaceboYesDouble-blind1,000 mg/day, adjustableUntil birthBaby's death, preterm birth or neonatal unit stay23% vs 27% (adjusted relative risk 0.85, 95% CI 0.62–1.15). Itch was 5.7 mm lower on a 100 mm scale.About three in four women had milder disease; stillbirth too rare to analyze alone.
Ovadia 2021[19]6,974 women in 34 studiesIndividual patient data meta-analysisNo UDCAMixed; randomized trials analyzed separatelyNot applicableAs in each studyNot applicableStillbirth; stillbirth or preterm birthStillbirth 0.7% vs 0.6% (adjusted OR 1.04). In randomized trials only, stillbirth or preterm birth was lower (adjusted OR 0.60, 95% CI 0.39–0.91).Stillbirth is rare; most of the data are not from randomized trials.
UDCA: fatty liver
Lindor 2004[12]166 people with fatty liver inflammation (NASH)RandomizedPlaceboYesNot stated13–15 mg/kg/day2 yearsLiver tests and biopsyFat, inflammation and scarring on biopsy did not differ significantly from placebo.40 of 166 did not finish; no effect sizes in the abstract.
Leuschner 2010[20]185 people with NASHRandomized, double-blindPlaceboYesDouble-blind23–28 mg/kg/day18 monthsLiver biopsyNo significant difference in overall biopsy findings; lobular inflammation and GGT improved.Subgroup findings exploratory.
Ratziu 2011[21]126 people with NASHRandomized, double-blind, multicenterPlaceboYesDouble-blind28–35 mg/kg/day12 monthsALTALT fell 28.3% vs 1.6% (p<0.001); a fibrosis blood test and markers of blood sugar control improved.No biopsy endpoint; blood measures only.
UDCA: primary sclerosing cholangitis
Lindor 1997[22]105 people with primary sclerosing cholangitisRandomized, double-blindPlaceboYesDouble-blind13–15 mg/kg/dayMedian 2.2 yearsTime to treatment failureNo significant difference (relative risk 1.01, 95% CI 0.6–1.7); liver tests improved on UDCA.Moderate size; about two years.
Olsson 2005[23]219 people with primary sclerosing cholangitisRandomized, multicenterPlaceboYesNot stated17–23 mg/kg/day5 yearsDeath or liver transplant7.2% vs 10.9% (P=.368); symptoms and quality of life did not differ.Enrolled 63% of its planned size, per AASLD.
Lindor 2009[13]150 people with primary sclerosing cholangitisRandomized, double-blind, multicenterPlaceboYesDouble-blind28–30 mg/kg/dayStopped after 6 yearsCirrhosis, varices, bile duct cancer, transplant or deathLiver tests improved, but endpoints were reached by 39% vs 26%; adjusted risk 2.3 times higher on UDCA (P<0.01). Stopped for futility.Stopped early; the harm appeared in a trial designed to show benefit.
Eaton 2011[54]56 people with sclerosing cholangitis and ulcerative colitis, from the 2009 trialSecondary analysis of a randomized trialPlaceboYes (parent trial)Double-blind (parent trial)28–30 mg/kg/day235 patient-yearsColorectal dysplasia or cancerHigher risk on high-dose UDCA (hazard ratio 4.44, 95% CI 1.30–20.10).A subgroup of a trial not designed for this outcome; small.
Download the table (CSV)

Taken from each study's published summary, or its full text where available. Searched October 20, 2026.

How we did this review

Search. On October 20, 2026 we searched PubMed, Europe PMC and ClinicalTrials.gov for every spelling of TUDCA alongside UDCA, and for UDCA in primary biliary cholangitis, gallstones, rapid weight loss, life after gallbladder removal, cholestasis of pregnancy, fatty liver and primary sclerosing cholangitis, logging 129 searches in all. We read the US labels for ursodiol, the approval records at Drugs@FDA, and practice guidance from the American Association for the Study of Liver Diseases, the European Association for the Study of the Liver, the European Society of Gastrointestinal Endoscopy and the Society for Maternal-Fetal Medicine. For the claims table, we read 14 pages from 11 supplement sellers and health sites on the same day.

What we included. Every published study in people that gave TUDCA and UDCA side by side. For UDCA, the main randomized trials, pooled analyses and guidelines for each use, rather than every UDCA study. Studies of TUDCA alone are appraised in our review of the TUDCA evidence. Lab and animal studies are named in the claims table but not appraised.

How we appraised them. For every study we recorded the same fields: who took part, the design, the comparison, whether it was randomized and blinded, the dose and length, what was measured, the result, and the main limits. We took them from the study itself, not from secondary sources, and wrote “not stated” where the study does not say. Doses are given as each study reported them.

How we graded the evidence. Each use gets two things for each bile acid: what the studies found, and a grade for how much research stands behind that finding. The grade describes the research, not the bile acid. A low grade means a finding has not yet been confirmed, not that it has been disproved.

  • Strong: consistent results from several well-sized randomized, blinded trials measuring outcomes that matter to patients.
  • Moderate: at least one well-sized randomized trial, with laboratory outcomes or short follow-up.
  • Early: one placebo-controlled trial, or several small controlled trials, or a licensed medical use resting on small trials.
  • Preliminary: one or two studies that were small, uncontrolled or unblinded.
  • Not yet studied: no published study in people.

Limits of this review. For several older studies we could read only the English summary; some full texts are in Italian or German. Two older TUDCA studies in people, from 1982, have no published summary and we could not read them; one may also have compared TUDCA with UDCA. We could not search Chinese-language databases (CNKI, Wanfang), Embase, or the WHO and Chinese trial registries, so head-to-head studies indexed only there may be missing. We did not find guidance on cholestasis of pregnancy from the American College of Obstetricians and Gynecologists to quote.

About this review

Who wrote it. The Dr.Primal editorial team. Our editorial standards explain how we work.

Conflict of interest. Dr.Primal sells a TUDCA supplement and does not sell UDCA. That is why we have kept this page free of product links and offers, reported results that favor UDCA alongside those that favor TUDCA, and appraised every study in the same way.

Medical review. This review has not been checked by a physician. The Dr.Primal editorial team wrote it and fact-checked every figure against its primary source. If a credentialed reviewer checks it later, we will name them here and record it in the version history.

Versions. Version 1.0, October 20, 2026: first publication. We will update this page when new studies are published, and record every change here.

Corrections. If you find an error or a study we missed, please tell us.

Cite this page Dr.Primal Editorial. TUDCA vs UDCA: differences and what's proven. Version 1.0. Dr.Primal; October 20, 2026. https://drprimal.com/en-gb/pages/tudca-vs-udca

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This review describes published research. It is not medical advice and does not replace advice from your doctor. UDCA is a prescription medicine; do not start, stop or change it without your doctor. Dietary supplements are not intended to diagnose, treat, cure or prevent any disease.

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