Diagnosing Gas in the Intestinal Tract

Gas in the intestinal tract is normal, and everyone passes a certain amount of gas in the form of flatulence or belching. Most often, gas is a product of eating certain foods or swallowing air. Many people think they pass too much gas when the amount that they have is actually normal. However, in some uncommon cases, excessive gas might truly need further investigation.

A doctor testing the stomach of woman
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When to See Your Healthcare Provider

If you think you're having too much gas, you'll want to see your primary healthcare provider. On the first visit to a healthcare provider about the problem of excess gas, being able to describe symptoms in detail will help in narrowing down the cause. Some questions a healthcare provider might ask about gas include:

  • Are you experiencing belching as well, or is flatulence the primary issue?
  • Has there been a recent change in how much gas you have?
  • Has the odor of your gas changed?
  • Are you experiencing actual belching or flatulence, or, instead, more bloating or a feeling of being full?

If your healthcare provider is unable to determine the cause of your problems with gas, you might be referred to a gastroenterologist for further evaluation.

Food and Symptom Diary

A healthcare provider may ask a person who is experiencing gas to record their diet and any symptoms, such as belching, bloating, and flatulence. By analyzing diet and the timing of symptoms, it may become clear that a particular food or activity is leading to the excess gas. If such a diary does not help to pinpoint the source of the gas, other tests might be used to help diagnose the problem.

Tests to Evaluate Gas

The following tests might further determine what is causing excess gas or bloating.

  • Abdominal X-ray: An X-ray of the abdomen will show if there is any gas in the intestinal tract, as well as its location. Both of these pieces of information will help your healthcare provider make a diagnosis.
  • Upper GI series: This test is done with barium and can illuminate any problems in the small intestine.
  • CT scan: A computed tomography (CT) scan, which is sometimes done with contrast dye that is given by mouth or by enema, gives a more complete picture of the abdomen than a flat X-ray.
  • Stool tests: If milk sugar or alcohol sugars are suspected of causing the gas, tests that show if there is too much fat in the stool might be ordered.
  • Breath tests: Breath tests can determine if hydrogen is being produced in the small intestine, which could be a sign of small intestine bacterial overgrowth (SIBO).

A healthcare provider may also order other tests to determine the cause of gas or bloating.

Swallowing Excess Air

One possible cause of frequent belching is swallowing excess air. There is no test to diagnose this problem, but the solution is in taking measures to prevent the swallowing of air. Not chewing gum or sucking on hard candy, and eating more slowly, can help reduce swallowed air. Sitting upright after eating can help prevent flatulence, and is especially helpful for people who have heartburn or gastroesophageal reflux disease (GERD).

Lactose Intolerance

Lactose intolerance is the inability to digest the sugar found in milk (lactose). It can either be congenital or acquired. Rarely, an infant is born unable to digest milk sugar, which can lead to feeding problems early in life. More commonly, lactose intolerance develops after about the age of 2 years. When lactose passes into the digestive tract undigested, it can lead to symptoms of gas, bloating, and diarrhea.

Diagnosing lactose intolerance could be as simple as abstaining from eating or drinking milk products for a time and observing if symptoms improve. If there is no change in the symptoms of gas, diarrhea, or bloating, then milk products are probably not the cause. There are also several tests that can be used to diagnose lactose intolerance, although they are not commonly used:

  • The lactose tolerance test, which measures blood glucose two hours after ingesting a lactose-containing drink.
  • The hydrogen breath test, which tests a person's breath for hydrogen after they drink a solution containing lactose.
  • The stool acidity test, which tests stool; people who are lactose-intolerant will have acidic stool.
  • The stool antigen test for infection by Helicobacter pylori, which can cause gastrointestinal symptoms.
  • The urea breath test for H. pylori.

If lactose intolerance is diagnosed, the treatment is avoiding all foods, medications, and beverages that contain lactose.

Sugar Alcohols

Sugar alcohols are sweeteners added to many foods in order to lower their calorie content, or to make them suitable to be consumed by people who have diabetes.

Sorbitol, maltitol, mannitol, and xylitol are a few of the sugar alcohol food additives that can cause gas and other digestive symptoms.

Sugar alcohols are not digested fully in the small intestine, and may pass into the large intestine, where they ferment and lead to symptoms of gas and diarrhea. Sorbitol is a sugar found naturally in certain fruits (such as apples, apricots, avocados, blackberries, cherries, nectarines, pears, and plums), and is created synthetically for use as a sugar substitute. Sorbitol and the other sugar alcohols can commonly be found in gum, candy, and other "sugar-free" foods.

Conditions That Cause Excess Intestinal Gas

In more rare cases, symptoms of gas, bloating, and pain might be caused by a disease or condition in the colon or the abdomen.

Celiac disease: Celiac disease is the inability of the body to digest gluten, which is the protein found in wheat. When a person who has celiac disease ingests gluten, a host of symptoms can occur, including excess gas and abdominal bloating. Testing for the presence of celiac disease is a process that includes blood testing, endoscopy with an intestinal biopsy, and sometimes genetic testing. The treatment for celiac disease is avoiding eating gluten.

Diabetes: One complication of diabetes is the slowing down of the process of digestion. Slow digestion could cause food to pass through the small intestine without being fully digested and consequently fermenting in the large intestine. Improper digestion could also cause SIBO (see below).

Scleroderma: Some forms of scleroderma can adversely affect the gastrointestinal tract. A number of intestinal dysfunctions can lead to symptoms of abdominal distention (bloating) and gas. Scleroderma can also be associated with SIBO (see below).

SIBO: SIBO is caused when bacteria from the large intestine back up into the small intestine and grow out of control. Too much bacteria in the intestines can result in gas and bloating. Digestive conditions that put someone at risk for SIBO include short bowel syndrome, irritable bowel syndrome, scleroderma, diabetes, and celiac disease.

A Word From Verywell

Gas is part of the normal digestive process and is, actually, a sign that the bowel is doing the work of digesting foods. Cutting back on gassy foods or drinking through a straw may help lessen gas for some people. If gas and bloating is excessive or becomes too uncomfortable, consult a general practitioner and discuss whether it might be time to see a gastroenterologist.

3 Sources
Verywell Health uses only high-quality sources, including peer-reviewed studies, to support the facts within our articles. Read our editorial process to learn more about how we fact-check and keep our content accurate, reliable, and trustworthy.
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  2. Deng Y, Misselwitz B, Dai N, Fox M. Lactose Intolerance in Adults: Biological Mechanism and Dietary ManagementNutrients. 2015;7(9):8020–8035. doi:10.3390/nu7095380

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Additional Reading

By Amber J. Tresca
Amber J. Tresca is a freelance writer and speaker who covers digestive conditions, including IBD. She was diagnosed with ulcerative colitis at age 16.