What is IMO?

Intestinal methanogen overgrowth or IMO occurs when there are too many methane producing microorganisms present in the gut. These microorganisms are single-celled microbes called archaea. Whilst archaea naturally occur in the intestines, their colonies can sometimes overgrow, producing much more methane than normal. Hence the condition is called “intestinal methanogen overgrowth”.

IMO can sometimes be misdiagnosed as small intestinal bacterial overgrowth (SIBO) and was once known as a sub-type of SIBO (1). However, SIBO is caused by bacteria, not archaea, and it only occurs in the small intestine, whereas methanogens can be present throughout the entire gut. SIBO is also more commonly associated with diarrhea, where IMO patients usually present with constipation (2).

What are the symptoms of IMO?

IMO causes non-specific gut symptoms such as bloating and abdominal pain. It’s generally associated with slow gut transit and constipation rather than loose stools (3). If no breath tests are performed, it can be misdiagnosed as constipation predominant irritable bowel syndrome (IBS-C) (4). IBS is a complex disorder of the gut-brain axis that you can read about in detail in our eBook.

How is IMO diagnosed?

Although methane is found in 30-50% of adults, people with higher levels of methane production have also been observed to suffer from gastrointestinal symptoms (5). The best way to diagnose IMO is for a doctor to check the levels of methane found in a patient’s breath (6). This can be performed using breath tests at the doctor’s office or by purchasing an OMED Health Breath Analyzer – which allow you to see the levels of both hydrogen and methane on your breath at any time, from the comfort of your home. If purchasing in the UK, an OMED Health doctor can also analyse your results and diagnose IMO if appropriate.

How can you treat IMO?

High levels of methane in the breath indicate abnormal amounts of methane producing archaea in the gut, suggesting that there is a dysbiosis. This imbalance of the gut microbiome can be treated with antimicrobials, or if needed, antibiotics (7). These treatments aim to reduce levels of archaea in the gut so that less symptom causing methane is produced. Some doctors may also advise a special diet to ease symptoms and figure out if certain foods should be avoided or eaten more regularly to support long term gut health (7). This may be followed by a specific supplement for gut recovery.

Have you already tested for IMO? Find out your next steps if you have either a positive or negative diagnosis in our other blogs:

It’s important to recognize that SIBO and IMO are conditions that can flare up without warning. If you’re prone to experiencing gut symptoms, we recommend getting an OMED Health Breath Analyzer, as it allows for repeated use, including long-term monitoring. The device works alongside the OMED Health App, enabling you to log breath data alongside symptoms and lifestyle factors such as diet, sleep, stress and exercise to help you take back control of your gut health.

References

1. Suri J, Kataria R, Malik Z, Parkman HP, Schey R. Elevated methane levels in small intestinal bacterial overgrowth suggests delayed small bowel and colonic transit. Medicine. 2018 May;97(21):e10554. doi: 10.1097/MD.0000000000010554
2. Methanogens in Human Health and Disease – ProQuest [Internet]. [cited 2025 Mar 18]. Available from: https://www.proquest.com/openview/6e81fbd35456ac77185043bf1d356321/1?cbl=2041980&pq-origsite=gscholar
3. Mehravar S, Takakura W, Wang J, Pimentel M, Nasser J, Rezaie A. Symptom Profile of Patients With Intestinal Methanogen Overgrowth: A Systematic Review and Meta-analysis. Clinical Gastroenterology and Hepatology [Internet]. 2024 Aug 13 [cited 2025 Mar 18];0(0). Available from: https://www.cghjournal.org/article/S1542-3565(24)00716-X/abstractdoi: 10.1016/j.cgh.2024.07.020
4. Takakura W, Pimentel M. Small Intestinal Bacterial Overgrowth and Irritable Bowel Syndrome – An Update. Front Psychiatry [Internet]. 2020 Jul 10 [cited 2025 Mar 18];11. Available from: https://www.frontiersin.org/journals/psychiatry/articles/10.3389/fpsyt.2020.00664/fulldoi: 10.3389/fpsyt.2020.00664
5. Triantafyllou K, Chang C, Pimentel M. Methanogens, Methane and Gastrointestinal Motility. J Neurogastroenterol Motil. 2014 Jan 31;20(1):31–40. doi: 10.5056/jnm.2014.20.1.31
6. Rezaie A, Buresi M, Lembo A, Lin H, McCallum R, Rao S, et al. Hydrogen and Methane-Based Breath Testing in Gastrointestinal Disorders: The North American Consensus. Official journal of the American College of Gastroenterology | ACG. 2017 May;112(5):775. doi: 10.1038/ajg.2017.46
7. Rej A, Potter MDE, Talley NJ, Shah A, Holtmann G, Sanders DS. Evidence-Based and Emerging Diet Recommendations for Small Bowel Disorders. Official journal of the American College of Gastroenterology | ACG. 2022 Jun;117(6):958. doi: 10.14309/ajg.0000000000001764