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Gas (flatulence)

Medically reviewed by Last updated on Apr 6, 2023.

What is Gas (flatulence)?

Harvard Health Publishing

Flatulence is the passage of intestinal gas (flatus) through the rectum. Passing gas is normal, and every human being does it at least 14 times a day, consciously or unconsciously. Sometimes flatulence happens more often than expected, and this can become an embarrassing problem. Extreme flatulence can even interfere with a person's ability to work and socialize comfortably with other people.

Most cases of flatulence are related to factors that can be controlled. This is because intestinal gas usually comes from two sources — swallowed air or the work of intestinal bacteria on undigested food.

Swallowing air is one cause of flatulence. Although much of this swallowed air is belched upward through the mouth, a small amount passes into the intestines and out through the rectum. People swallow air in many different ways, particularly by:

Bacteria in the intestines also can produce gas when they process foods that pass into the colon without being digested higher up in the digestive tract. Some common examples of foods that tend to cause gas include:

Less commonly, flatulence can be a side effect of certain medications, especially cholestyramine (Questran), used to treat high cholesterol, or the diet drug orlistat (Xenical). It also can be a symptom of irritable bowel syndrome or giardiasis (a parasitic infection).


Flatulence is the passing of intestinal gas, either voluntarily or involuntarily. Some people who have flatulence also complain of abdominal bloating, but others do not.


Usually a person with flatulence is aware of passing gas. Sometimes, it is more troublesome to other family members or co-workers.

To investigate the cause, examine your lifestyle, especially the way you eat your meals:

Expected duration

How long flatulence lasts depends on its cause. If flatulence is related to eating habits or dietary factors, it often goes away quickly once you identify the source of the problem and make the necessary changes in diet or lifestyle.


You often can prevent flatulence by modifying your eating habits and diet:


You may reduce flatulence by trying:

Treatment options

The following list of medications are in some way related to or used in the treatment of this condition.

View more treatment options

When to call a professional

Call your doctor if you have flatulence that occurs along with abdominal discomfort, significant bloating or a sudden change in your bowel habits, either constipation or diarrhea. Also, call for advice if your attempts to reduce your flatulence have not worked.


Flatulence often can be controlled with a few minor changes in diet or lifestyle.

Additional info

National Institute of Diabetes and Digestive and Kidney Disorders

American College of Gastroenterology (ACG)

American Gastroenterological Association

Learn more about Gas

Treatment options

Further information

Always consult your healthcare provider to ensure the information displayed on this page applies to your personal circumstances.