Ursodiol is a medication that mimics a naturally occurring bile acid in your body. It’s primarily used to treat a chronic liver disease called primary biliary cholangitis (PBC) and to dissolve certain types of gallstones without surgery. Beyond these two FDA-approved uses, doctors also prescribe it to prevent gallstones during rapid weight loss, such as after bariatric surgery.
How Ursodiol Works
Your liver produces bile acids to help digest fats and absorb nutrients. Ursodiol is a synthetic version of one of these bile acids, and it makes up a small fraction of your body’s natural bile acid pool. When you take it as a medication, it gradually shifts the overall composition of your bile, making it less concentrated with cholesterol. This matters because cholesterol-heavy bile is what causes most gallstones to form and what damages bile ducts in certain liver diseases.
In the liver, ursodiol also has a protective effect on the cells lining your bile ducts. It reduces the toxicity of harsher bile acids that accumulate when bile flow is impaired, which is why it’s so effective for liver conditions involving blocked or inflamed bile ducts.
Treating Primary Biliary Cholangitis
Primary biliary cholangitis (PBC) is a chronic autoimmune disease where the immune system slowly destroys the small bile ducts inside the liver. Without treatment, bile backs up, damages liver tissue, and can eventually lead to cirrhosis and liver failure. Ursodiol is the first-line treatment for PBC at any stage of the disease, as long as liver blood tests remain abnormal.
The evidence behind this use is strong. A large international analysis of nearly 5,000 patients found that people treated with ursodiol had significantly better transplant-free survival compared to untreated individuals. At 10 years, 78% of treated patients were alive without needing a transplant, compared to 59% of those who went untreated. At 15 years, the gap widened further: 66% versus 32%. Multiple randomized trials and long-term studies have confirmed that ursodiol improves liver enzyme levels, slows the progression of liver scarring, and reduces the need for liver transplantation.
Most people notice improvements in their liver blood tests within a few weeks of starting treatment. About 90% of the biochemical improvement happens within the first six to nine months. Roughly 20% of patients see their liver tests return completely to normal after two years. For PBC, ursodiol is taken long-term, typically for life, at a weight-based dose taken in divided portions with food.
Dissolving Gallstones Without Surgery
Ursodiol can dissolve gallstones, but only a specific type. The stones must be cholesterol-based (not calcified), smaller than 20 millimeters across, and sitting in a gallbladder that still functions. Calcified stones, which appear bright on imaging, do not respond to ursodiol. Neither do stones larger than 20 millimeters.
This use is typically reserved for people who aren’t good candidates for gallbladder removal surgery, whether because of age, other medical conditions, reactions to anesthesia, or personal preference.
Dissolving gallstones with ursodiol is a slow process. It takes months of daily treatment, and success rates depend heavily on stone size. For stones 5 millimeters or smaller, complete dissolution occurs in about 81% of patients. Across all eligible patients with uncalcified stones under 20 millimeters, the overall success rate is around 30% over up to two years. That number climbs to about 50% for “floating” stones, which tend to have higher cholesterol content and respond better to treatment.
Timing gives you useful clues about whether the medication is working. If imaging shows partial dissolution within six months, there’s a greater than 70% chance of complete dissolution with continued treatment. If there’s still no sign of shrinkage at 12 months, the odds of success drop considerably, and your doctor will likely reassess the approach.
Preventing Gallstones During Rapid Weight Loss
Losing weight quickly is one of the strongest risk factors for developing gallstones. When the body breaks down fat rapidly, the liver secretes extra cholesterol into bile, and the gallbladder may not empty as efficiently. This combination creates ideal conditions for stones to form. After bariatric surgery, the risk is high enough that many surgeons prescribe ursodiol as a preventive measure.
A meta-analysis of randomized controlled trials found that a daily dose of 600 milligrams or less reduced the risk of gallstone formation by about 65% compared to placebo. This dosage also showed better patient compliance than higher doses. A dose of 500 to 600 milligrams per day appears effective regardless of the type of bariatric surgery performed. Doctors typically continue the prescription for six months after surgery, covering the period of most rapid weight loss.
Use During Pregnancy
Some pregnant women develop a liver condition called intrahepatic cholestasis of pregnancy (ICP), which causes intense itching and elevated bile acid levels. Ursodiol has been widely prescribed for this condition, but the evidence supporting it is weaker than many people assume.
The largest randomized controlled trial on this topic, published in The Lancet, found that ursodiol did not produce a clinically meaningful reduction in itching, did not lower maternal bile acid levels, and did not clearly improve outcomes for the baby. Earlier, smaller studies had suggested benefits, but a Cochrane systematic review concluded that definitive evidence for improved fetal outcomes was absent. Despite this, some physicians still prescribe it because the medication appears safe during pregnancy and treatment options for ICP are limited.
Side Effects
Ursodiol is generally well tolerated. In clinical trials comparing it to placebo, the difference in side effects between the two groups was minimal. The most commonly reported side effects (occurring in 1% or more of patients) include abdominal discomfort, abdominal pain, diarrhea, nausea, itching, rash, and hair thinning. Digestive symptoms like constipation, indigestion, and vomiting have also been reported, though less frequently.
Hair thinning can be alarming when it happens, but it’s uncommon and typically reversible. Most people taking ursodiol for PBC or gallstone dissolution tolerate it without significant problems over months or even years of continuous use.
Who Should Not Take Ursodiol
Ursodiol is not appropriate for everyone with gallstones. If your stones are calcified, larger than 20 millimeters, or if your gallbladder isn’t visible on imaging (suggesting it’s no longer functioning), the medication is unlikely to work. People with a blocked bile duct, a bile duct fistula, or pancreatitis should not take it. You should also let your doctor know if you have any allergies to bile acid medications before starting treatment.