A carbohydrate breath test is a non-invasive diagnostic tool used to investigate various digestive complaints. This test measures the levels of specific gases, primarily hydrogen and methane, in a person’s breath. These gases are produced when certain sugars are fermented by bacteria in the digestive tract. The test helps healthcare providers understand how a person’s body processes different carbohydrates after a specific sugar solution is consumed.
Conditions Diagnosed with the Test
This test is frequently used to identify Small Intestinal Bacterial Overgrowth (SIBO), a condition where there is an excessive amount of bacteria in the small intestine. When bacteria in the small intestine ferment carbohydrates, they produce hydrogen and methane gases, which are then absorbed into the bloodstream and exhaled. An early and significant rise in these gas levels after ingesting a test sugar like glucose or lactulose points to SIBO.
Carbohydrate malabsorption is another primary condition diagnosed using this method. This occurs when the small intestine cannot properly break down or absorb certain sugars. Common types include lactose intolerance, where the body lacks the enzyme lactase to digest lactose (milk sugar), and fructose malabsorption, an inability to absorb fructose (fruit sugar) efficiently. The breath test helps differentiate these by using specific sugar challenges; for instance, a lactose breath test assesses lactose digestion.
The Testing Process
Preparation for a carbohydrate breath test ensures accurate results. Patients are instructed to follow a specific low-fermentation diet for 24 to 48 hours before the test. This dietary restriction reduces background gas production from the gut, which can interfere with test clarity. Foods high in fermentable carbohydrates, such as fiber, complex sugars, and certain dairy products, are avoided during this preparation period.
Following the dietary preparation, a fasting period of at least 8 to 12 hours is required before the test begins. During the test, a baseline breath sample is collected, then the patient drinks a measured solution containing a specific carbohydrate like glucose, lactulose, lactose, or fructose. Subsequent breath samples are collected at regular intervals, every 15 to 20 minutes, over a period of two to three hours. Some individuals may experience digestive symptoms like bloating, abdominal discomfort, or gas during the test, as carbohydrate fermentation is an expected part of the process.
Interpreting Test Results
Gastroenterologists analyze the collected breath samples by looking for a significant increase in hydrogen or methane gas levels above the initial baseline reading. The timing of this gas increase helps pinpoint the location of the fermentation within the digestive tract.
An early and rapid rise in hydrogen or methane levels within the first 90 minutes of the test suggests the presence of Small Intestinal Bacterial Overgrowth (SIBO). This early rise indicates that bacteria are fermenting the carbohydrate in the small intestine, rather than the expected fermentation occurring later in the large intestine. In contrast, a later rise in gas levels after 90 minutes or more points towards carbohydrate malabsorption, as the sugar has traveled further down the digestive tract to the large intestine before being fermented by colon bacteria. This information allows healthcare providers to connect a “positive” result to specific conditions, guiding appropriate treatment plans.