Symptoms & Causes of Gas in the Digestive Tract

In this section:

What are the symptoms of gas?

Gas symptoms vary from person to person. Common symptoms of gas in the digestive tract include belching, bloating and distention, and passing gas. Having some gas symptoms is normal, especially during or after meals.

Gas symptoms may be a problem if they occur often, bother you, or affect your daily activities.

Belching

Belching, or burping, is a release of gas from your stomach through your mouth. People typically belch up to 30 times a day.3

Some people may feel they belch more often than normal. In some cases, people belch a lot because they swallow too much air and release the air before it enters the stomach.

Bloating and distention

Bloating is a feeling of fullness or swelling in your abdomen, or belly. If your abdomen becomes larger than usual, doctors call this distention. Only about half of people with bloating also have distention.4,5 Some people may also feel abdominal discomfort or pain when they have bloating or distention.

Passing gas

Studies suggest that people pass gas through the anus an average of 8 to 14 times a day.6 However, some people may pass gas more often. Experts consider passing gas up to 25 times a day to be normal.6,7

Excess gas in the digestive tract that leads to passing gas is called flatulence. The gas that passes is called flatus. People who have problems with flatulence may feel they pass too much gas or that the flatus has an unpleasant odor. The odor may be due to sulfur in the flatus.

When should I talk with a doctor about my gas symptoms?

You should talk with your doctor if

  • gas symptoms bother you
  • your symptoms change suddenly
  • you have other symptoms—such as abdominal pain, constipation, diarrhea, or weight loss—along with gas symptoms
A man pressing one hand against his abdomen.You should talk with your doctor if gas symptoms bother you.

What causes gas?

Gas normally enters your digestive tract when you swallow air and when bacteria in your large intestine break down undigested carbohydrates. You may have more gas symptoms if you swallow more air or consume more of certain foods and drinks.

Swallowed air

Everyone swallows a small amount of air when eating and drinking. Swallowed air that doesn’t leave your stomach when you belch may move into your intestines and pass through your anus.

Swallowing more air may lead to more gas and gas symptoms. You swallow more air when you

  • chew gum or suck on hard candy
  • drink carbonated, or fizzy, drinks
  • eat or drink too fast
  • smoke
  • wear loose-fitting dentures

Bacteria in your large intestine

Your large intestine contains a large number of bacteria and some fungi and viruses that make up the gut microbiome—the microbes in your digestive tract that help with digestion. Bacteria in the large intestine help break down carbohydrates and create gas in the process.

Certain foods and drinks contain types of carbohydrates—sugars, starches, and fiber—that your stomach and small intestine don’t fully digest. Undigested carbohydrates will pass to your large intestine, where bacteria break them down and create gas. You may have more gas symptoms if you consume more carbohydrates that your stomach and small intestine don’t fully digest.

What health conditions can cause problems with gas symptoms?

Some health conditions can cause you to have more gas than usual or have more gas symptoms.

IBS and other functional GI disorders

Functional gastrointestinal (GI) disorders such as irritable bowel syndrome (IBS), functional abdominal bloating and distention, functional constipation, and functional dyspepsia may cause problems with gas symptoms.

Functional GI disorders are related to problems with how your brain and your gut work together. These problems can cause you to feel more bloating or abdominal pain or can affect how gas moves through your intestines.

Problems digesting carbohydrates

People who have problems digesting certain carbohydrates may experience digestive symptoms—such as bloating, abdominal pain, and diarrhea—after they consume certain foods or drinks. Problems digesting carbohydrates include

  • lactose intolerance, in which people have digestive symptoms after consuming foods or drinks that contain lactose
  • dietary fructose intolerance, in which people have digestive symptoms after consuming foods or drinks that contain fructose

Small intestinal bacterial overgrowth

Small intestinal bacterial overgrowth is an increase in the number of bacteria or a change in the type of bacteria in your small intestine. These bacteria can produce extra gas and may also cause diarrhea and weight loss. Small intestinal bacterial overgrowth is most often a complication of other health conditions.

Other digestive diseases and conditions

A number of other digestive diseases and conditions may lead to more gas or gas symptoms, including

References

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. The 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 the NIDDK is carefully reviewed by NIDDK scientists and other experts.