SIBO (Small Intestinal Bacterial Overgrowth)

Normally the human small intestine is sparsely colonised by bacteria in comparison to the colon. Structural or functional disorders of the gastrointestinal tract can lead to bacterial overgrowth in the small intestine, with colonic bacteria proliferating in the ileum and jejunum. Small intestinal bacterial overgrowth (SIBO), as it is known, is characterized by steatorrhea and diarrhoea, together with vitamin deficiencies and carbohydrate malabsorption as the overgrowth causes damage to the absorptive surface of the intestine. The syndrome is difficult to diagnose with accuracy using blood tests.

Bacteria growing in the intestine can break down carbohydrates to produce hydrogen and methane, which are rapidly transported to the lungs via the portal blood supply and the liver. The sole source of these gases in alveolar air is bacterial fermentation of carbohydrate in the gut, so estimation of hydrogen and methane in breath samples can be used to study the passage of carbohydrates through the gut and the presence of pathogenic bacteria in the gastro-intestinal lumen.


Breath testing to aid in the diagnosis of small intestinal bacterial overgrowth (SIBO) may also provide a framework for the understanding of irritable bowel syndrome (IBS). Recent work has demonstrated that among IBS subjects, methane production in the lactulose breath test is associated with constipation.

Specimen requirements: alveolar breath samples. Collection bags are available for postal samples.

Turn around time: 5-10 working days