Ursodeoxycholic acid (UDCA) 150 mg is a prescription medicine containing ursodeoxycholic acid, a naturally occurring bile acid. Uses It is commonly prescribed for: Certain gallstones, particularly cholesterol-containing stones, when appropriate Primary biliary cholangitis (PBC) Some other liver or bile-flow disorders, depending on the doctor's assessment How it works UDCA changes the composition of bile and can improve bile flow. It may reduce the amount of cholesterol in bile and, in selected patients, help dissolve cholesterol gallstones.