How Do Gallstones Form?

Gallstones. Credit: BSIP / Contributor / Getty Images

If you've been diagnosed with gallstones, you may be wondering how exactly gallstones form. Your gallbladder is a small, pair-shaped organ, which stores bile, a liquid produced by your liver. Your gallbladder sits below your liver on the upper right side of your body between your chest and your hips.

Typically, bile helps your body digest fats and fat-soluble vitamins. After eating fats, your gallbladder contracts, pushing the stored bile into the common bile duct, which brings the liquid to your small intestine to aid digestion.

Gallstones form when there are imbalances in the substances that make up bile –– either too much cholesterol or bilirubin or not enough bile salts. This imbalance causes the liquid bile to harden and change to hard pieces of stone-like material, thereby blocking the common bile duct. Gallstones can range in size, from something as small as a grain of sand to as large as a golf ball. You can have one large gallstone, multiple smaller gallstones, or a combination of both large and small stones. It is possible to have dozens to hundreds of smaller gallstones.

Women are more likely to develop gallstones than men. Age also increases your risk of gallstones, with people over the age of 40 being more likely to develop these stones. Dietary changes and being overweight can also put you at risk of developing gallstones. Certain digestive and endocrine conditions, such as Crohn's disease and diabetes, can also raise your risk.

If gallstones run in your family, this too can increase your likelihood of developing the condition.

Types of Gallstones

Eighty percent of gallstones are classified as either cholesterol stones or pigment stones.

  • Cholesterol Stones: The medical community’s current belief is that cholesterol stones are the result of bile that is made of too much cholesterol or bilirubin and not enough bile salts. Cholesterol stones may also form when the gallbladder fails to empty during the digestive process.
  • Pigment Stones: Medical science remains unsure of what causes pigment stones in the gallbladder. Those who develop pigment stones are typically people who have cirrhosis of the liver, biliary tract infections, and hereditary blood disorders, including sickle cell anemia. These are all conditions that cause too much bilirubin. Pigment stones are darker in color than cholesterol stones.

Symptoms of Gallstones

If you have gallstones, you may experience what is known as a gallbladder attack. Attacks usually occur after eating and can last anywhere from one to several hours. Symptoms of a gallbladder attack include:

  • Nausea and vomiting 
  • Upper abdominal pain or cramping (typically felt on the right side)
  • Indigestion

If you have any of the following more serious symptoms, seek medical attention immediately as these can indicate a serious blockage or inflammation:

  • Tea-colored urine
  • Pale stools
  • Fever
  • Yellowing of the skin or whites of eyes (jaundice)

Some people never experience symptoms and have what is known as asymptomatic or "silent" gallstones. In most cases, gallstones are treated by removing the gallbladder. If you do not have any symptoms, treatment may not be necessary.


NIH. National Institute of Diabetes and Digestive and Kidney Diseases. Gallstones. (2013).