Volume 30, Issue 173, July 2026

Breath testing in SIBO and IMO: interpretation and evidence-informed clinical approach

Jakub Majcherek^1♦, Tomasz Karwowski², Maciej Świerczyna³, Agata Olecka⁴, Filip Gałązka⁵, Fryderyka Orawczak⁶, Julia Gałązka⁷, Mateusz Mazurek⁸, Mikołaj Kotusiewicz⁹, Zuzanna Czuba⁸

¹Voivodeship Hospital in Tarnów, Lwowska Street 178A, 33-100 Tarnów, Poland
²Voivodeship Hospital in Płock, Medyczna Street 19, 09-400 Płock, Poland
³Ministry of the Interior and Administration Hospital, Północna Street 42, 91-425 Łódź, Poland
⁴7th Military Naval Hospital, Polanki Street 117, 80-305 Gdańsk, Poland
⁵Copernicus PL Sp. z o.o., St. Adalbert Hospital, Aleja Jana Pawła II 50, 80-462 Gdańsk, Poland
⁶Medical University of Łódź, Aleja Tadeusza Kościuszki 4, 90-419 Łódź, Poland
⁷Cardinal Stefan Wyszyński University in Warsaw, Wóycickiego Street 1/3, 01-938 Warsaw, Poland
⁸Medical University of Warsaw, Żwirki i Wigury Street 61, 02-091 Warsaw, Poland
⁹Jagiellonian University Collegium Medicum, Świętej Anny Street 12, 31-008 Kraków, Poland

^♦Corresponding author
Jakub Majcherek, Voivodeship Hospital in Tarnów, Lwowska Street 178A, 33-100 Tarnów, Poland

ABSTRACT

Interpretation of breath tests is, however, difficult, because positive results need to be interpreted, including the whole clinical presentation. Tests do not directly show the exact localization of fermentation. These results are estimated based on intestinal transit time. This narrative review gathers currently available guidelines, meta-analyses, and systematic reviews to present a wide spectrum of information about the biological basis, indications, process of testing, and clinical meaning in the context of SIBO and IMO. Difficult interpretation of positive results restrains the indications of glucose and lactulose breath tests to symptomatic patients. For many patients, there are additional factors like motility issues, altered anatomy, history of surgeries or presentation with predominant constipation or diarrhea phenotype. Both glucose and lactulose testing protocols have their own specification that affects interpretation. For example, lactulose testing is more prone to being affected by intestinal transit because it is not absorbed from the intestinal lumen. Intestinal methane overgrowth (IMO) should be considered as another entity. Studies show that, in patients with constipation, the presence of methanogenic archaea is associated. All of this shows that the results of breath testing need to be interpreted with the patient's whole clinical presentation, but technical factors like baseline gas values, transit-related factors, or used substrate need to be included. Future studies should focus on standardization, the three-gas testing method, and the development of validation methods.

Keywords: small intestinal bacterial overgrowth; intestinal methanogen overgrowth; breath testing; hydrogen; methane

Medical Science, 2026, 30, e137ms3937

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DOI: https://doi.org/10.54905/disssi.v30i173.e137ms3937

Published: 29 July 2026