Too much cholesterol in the bile : Normally, the chemicals in your bile are sufficient to break down the cholesterol your liver excretes. However, if your liver excretes more cholesterol than your bile can break down, it may crystallize and eventually turn into stones.
Too much bilirubin in the bile : The chemical bilirubin is created when your body breaks red blood cells. Your liver produces too much bilirubin under some circumstances, such as liver cirrhosis, biliary tract infections, and certain blood diseases. Gallstone development is influenced by excess bilirubin.
Incomplete emptying of the gallbladder : Bile can concentrate and turn into gallstones if the gallbladder does not empty properly.
Factors that may increase the risk of having gallstones are :
Gallstones are more common in women
People older than 40 years old
Family history of gallstones
Obesity
Use of medicines that contain estrogen (such as birth control pills)
Pregnancy
Lack of physical activity
Diabetes
Liver cirrhosis
Rapid weight loss by surgical intervention