Definition & Facts for Gas in the Digestive Tract

What is gas?

A gas is a substance that has no fixed size or shape. When inside a closed container, a gas will expand to fill the container. An example of gas is the air you breathe.

The gas inside your digestive tract is made of air and other gases. Gas typically leaves your digestive tract through your mouth when you belch—or burp—or through your anus when you pass gas. Having gas and some gas symptoms is normal. Many people are bothered by gas symptoms once in a while.

However, some people have repeated gas symptoms that bother them often or affect their daily activities. People may have problems with gas symptoms because they

  • have excess gas in the digestive tract
  • feel more severe gas symptoms, even when a normal amount of gas is in the digestive tract

How common is gas?

Everyone has gas in the digestive tract, and many people have problems with gas symptoms. For example, research suggests that 16% to 31% of people experience bloating—a feeling of swelling or fullness in the abdomen.1 In a large U.S. survey, about 20% of participants said they experienced bloating in the past week.2

Who is more likely to have problems with gas symptoms?

Some people are more likely to have problems with gas symptoms if they have certain health conditions. People who swallow more air or eat more of certain foods may also have more gas symptoms.


Last Reviewed June 2021
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This content is provided as a service of the National Institute of Diabetes and Digestive and Kidney Diseases (NIDDK), part of the National Institutes of Health. NIDDK translates and disseminates research findings to increase knowledge and understanding about health and disease among patients, health professionals, and the public. Content produced by NIDDK is carefully reviewed by NIDDK scientists and other experts.