Gas is air in the intestine that is passed through the rectum. Air that moves from the digestive tract through the mouth is called belching.

Gas is also called flatus or flatulence .

Flatulence; Flatus

Gas is normally formed in the intestines your body digests food.

Gas can make you feel bloated. It can cause crampy or colicky pains in your belly. See: Abdominal pain.

Gas can be caused by certain foods you eat. You may have gas if you:

• Eat foods that are difficult to digest, such as fiber. Sometimes, adding more fiber into your diet can cause temporary gas. Wait a little bit. Your body may adjust and stop producing gas.
• Eat or drink something your body cannot tolerate. For example, some people have lactose intolerance and cannot eat or drink dairy products.

Other common causes of gas are:

• Antibiotics
• Irritable bowel syndrome
• Your body cannot absorb or digest nutrients properly (malabsorption)
• Swallowing air while eating

The following tips may help you prevent gas:

• Chew your food more thoroughly
• Do not eat beans or cabbage
• Do not drink carbonated beverages
• Do not chew gum
• Eat more slowly
• Relax while you eat
• Walk for 10-15 minutes after eating

Call your doctor or nurse if you have:

• Gas and other symptoms such as stomach pain, rectal pain, heartburn, nausea, vomiting, diarrhea, constipation, or weight loss
• Oily, foul-smelling, or bloody stools

Your doctor or nurse will perform a physical examination and ask questions about your medical history and symptoms, such as:

• What is your diet like?
• Has it recently changed?
• What foods do you eat commonly?
• What foods have you eaten recently?
• Have you increased the fiber in your diet?
• How fast do you eat, chew, and swallow?
• Would you say that your gas is mild or severe?
• Does your gas seem to be related to eating milk products or other specific foods?
• What seems to make your gas better?
• What medications do you take?
• Do you have other symptoms like abdominal pain, diarrhea, early satiety (premature fullness after meals), bloating, or weight loss?

Tests that may be done include:

• Abdominal CT scan
• Abdominal ultrasound
• Barium enema x-ray
• Barium swallow x-ray
• Blood work such as CBC or blood differential
• Sigmoidoscopy
• Upper endoscopy (EGD)

Bailey J. FPIN's Clinical Inquiries: Effective management of flatulence. Am Fam Physician. 2009;79:1098-1100.

Ohge H, Levitt MD. Intestinal gas. In: Feldman M, Friedman LS, Brandt LJ, eds. Sleisenger & Fordtran's Gastrointestinal and Liver Disease. 9th ed. Philadelphia, Pa: Saunders Elsevier;2010:chap 16.