What is ursodeoxycholic acid?
Ursodeoxycholic acid is an endogenous, hydrophilic bile acid used as a medication. It displaces more aggressive, fat-loving bile acids from the bile acid pool, improves bile flow and thereby protects the liver cell. In humans it naturally makes up only a few percent of the pool; under therapy its share rises considerably.
The documented indication is primary biliary cholangitis. There it measurably improves laboratory values and histology. It is also used to dissolve cholesterol gallstones.
This information is for research and educational purposes only. No medical advice.
Comparison
Three approaches around the liver
As described in the TPD lexicon. Tap a card to open its entry.
Simplified: only ursodeoxycholic acid is approved for liver disease. A controlled trial as liver protection with oral anabolic steroids exists for none of the three. 63
How it works
The mechanism acts on bile flow, not on hepatocyte metabolism. That is the decisive sentence for its use with oral compounds. Ursodeoxycholic acid can favourably influence cholestasis, meaning a backup of bile. But it cannot prevent the direct cell damage from 17-alpha-alkylated compounds, because that runs through a different route.
Anyone who thinks UDCA lets them run a longer or higher oral cycle has misunderstood the mechanism. The protection it offers addresses one particular kind of liver load, not all of them.
Where it acts
Where ursodeoxycholic acid acted in studies
Tap a point or a card. Colour = bile acid receptor FXR, grey = observed in studies.
- Liver and bile ducts
Displaces more toxic bile acids, protects bile duct cells, stimulates bile flow5
FXR - Liver values in blood
Bilirubin and alkaline phosphatase fell versus placebo3
Observed in trials - Small intestine
Absorbed in the small intestine, distributed mainly in bile and gut5
Observed in trials
Targets in the ChEMBL database8
Compound CHEMBL1551: one recorded mechanism, Agonist according to ChEMBL.
- Gene
- NR1H4
- UniProt
- Q96RI1
- ChEMBL
- CHEMBL2047
- Action
- Agonist according to ChEMBL
Use and dosing
Dosing
Dosing, titration and syringe
Loading the dosing information …
- Getting started and stepping up, drawn as a staircase
- Units on the U-100 syringe for every step
- How long one vial lasts
What the research shows
For the approved indication the picture is clear. The controlled trial in NEJM (1991) showed markedly less treatment failure in 146 patients with primary biliary cholangitis, along with significantly better bilirubin and alkaline phosphatase. The Hepatology analysis (2008) showed that patients with a biochemical response in the first year had 90 percent transplant-free ten-year survival, versus 51 percent in non-responders.
The Cochrane review (2012) puts that in perspective: across 16 trials with 1,447 patients, no significant effect on all-cause mortality or transplantation was found. What improved were laboratory values and histology, not the hard endpoints.
The most important finding for caution comes from a different disease. In the Lindor trial (Hepatology 2009) in primary sclerosing cholangitis, high-dose ursodeoxycholic acid improved liver values and still worsened the hard endpoints, with a 2.3-fold increased risk. The trial was terminated. Better laboratory values under UDCA are therefore not proof of organ protection. That is the most important sentence on this page.
Study results
What the trials measured
Interactive: switch tabs, tap points, show or hide arms. Arms are named relative to each other, no dosing advice.
Treatment failure within two years1
146 patients with primary biliary cholangitis, share with treatment failure
6 of 73 versus 13 of 73, converted to percent. Bilirubin, alkaline phosphatase and the liver enzymes fell clearly, tissue findings improved, fibrosis did not.
Ten years without transplant2
292 patients with primary biliary cholangitis, all on ursodeoxycholic acid
Response after one year meant alkaline phosphatase below three times, AST below twice the upper limit and normal bilirubin. A comparison among patients, not a placebo trial.
Hard endpoints and tissue3
Pooled randomised trials in primary biliary cholangitis, share with event
Death and transplant without difference, an advantage in tissue stage. All trials but one had a high risk of bias.
Hard endpoints in primary sclerosing cholangitis4
150 adults, high dose versus placebo, stopped after six years
Liver values fell more under the high dose, yet more patients reached an endpoint. After adjustment the risk was 2.3 times higher.
Research status
Where the research stands
Ursodeoxycholic acid has been approved in the US since 1987. On ClinicalTrials.gov 221 trials list it among their interventions, mostly as background treatment next to new drugs. The 1991 NEJM trial is older than the registry. Shown are trials in which ursodeoxycholic acid itself was tested. As of 26 Oct 2026. 7
- Preclinical The body's own water-loving bile acid made from cholesterol
- Phase 1 no registered trial
- Phase 2 no registered trial
- Phase 3 1 trial, 0 completed, 1 stopped early
- Approval in the US since 1987
Show all 2 phase 3 and 4 trials on a timelineHide timeline
NCT00059202 · 150 participants, started Jul 2002, stopped early Jun 2008.
Registry entry ↗ · Results: Lindor et al., Hepatology, 2009
NCT01510860 · 65 participants, started Nov 2008, primary endpoint reached Jul 2010.
Registry entry ↗ · Results not yet in PubMed
Bar: start to primary endpoint (planned for running trials). Green = completed, blue = progress until 26 Oct 2026, grey = stopped early.
Side effects
- Diarrhoea: the most common report, usually mild and dose-dependent.
- Nausea and abdominal pain: occasional, mostly at the start.
- Otherwise well tolerated: tolerability is the uncontested plus point of this substance.
- What it cannot do: prevent the direct cell damage from 17-alpha-alkylated compounds.
Tolerability
Side effects compared with placebo
From the Cochrane review (primary biliary cholangitis) and the high-dose trial in primary sclerosing cholangitis.
| Event | Placebo | Ursodeoxycholic acid |
|---|---|---|
| Serious adverse events (PBC)3 | 16% | 14% |
| Non-serious adverse events (PBC)3 | 3% | 4% |
| Serious adverse events (PSC, high dose)4 | 37% | 0% |
At the usual dose side effects were at placebo level. At a high dose over years serious events were clearly more common. The US label lists diarrhoea as a common report.345
Storage
Store dry, at room temperature and protected from light. Keep out of reach of children.
