Small Intestinal Bacterial Overgrowth (SIBO) is a gastrointestinal condition where an abnormal number of bacteria is found in the small intestine. Whilst small amounts of bacteria are normal, higher levels can cause uncomfortable digestive issues. SIBO can impact nutritional absorption and affect hydration. In this article, we will take a closer look at the impact of SIBO and how Hydrogen and Methane Breath Testing (HMBT) can aid in a diagnosis.
What is SIBO?1
SIBO is a condition characterised by elevated bacterial levels in the small intestine. This excess amount of bacteria ferments food and interferes with digestion. Common causes of SIBO include:
- Motility issues: Slowed gut movement from conditions like irritable bowel syndrome (IBS), diabetes, or surgery.
- Low stomach acid: Reduced acid allows bacteria to survive and travel to the small intestine.
- Structural problems: Adhesions, scarring, or bowel surgery.
There are different types of SIBO, categorised by the primary gas produced. Hydrogen-dominant, methane-dominant and mixed SIBO are the most common forms. SIBO causes various uncomfortable symptoms, such as:
- Bloating,
- Abdominal pain,
- Diarrhoea or constipation,
- Excess gas,
- Fatigue.
These symptoms can significantly impact a person’s quality of life, underscoring the need for an accurate diagnosis.
Why diagnosis matters.2,3
Symptoms of SIBO can overlap with many other gut conditions, mimicking conditions like IBS, Chron’s disease and coeliac disease. Given the significant overlap in symptoms, a definitive diagnosis is crucial. SIBO is frequently misdiagnosed, and this can lead to inappropriate treatments and ongoing symptoms; an early diagnosis can improve patient outcomes. The primary test for SIBO is a non-invasive HMBT.
What is HMBT?4
A Hydrogen and Methane Breath Test (HMBT) is a non-invasive diagnostic method for measuring hydrogen and methane concentrations in exhaled breath. As approximately 30%–62% of the adult population are methane producers5, there is a clear need for HMBT methods that reliably detect both gases.
Prior to the test, the patient must follow a strict protocol that includes a fasting period. On the day of the test, the patient will be asked to do the following:
- Drink a sugar solution like lactulose or glucose.
- Exhale into an HMBT device at certain timed intervals.
Hydrogen and methane are the gases produced when bacteria ferment food prematurely in the small intestine. High levels of these gases can indicate elevated bacterial levels and support a diagnosis of SIBO.
What happens after diagnosis?6
Once a diagnosis has been confirmed, SIBO can be treated by either:
- Antibiotics,
- Dietary changes,
- Addressing the root cause.
A HMBT allows healthcare professionals to target treatment options, providing the best outcome for the patient.
SIBO is a common condition, but it is often overlooked due to overlap in symptoms. It can affect nutrient absorption, leading to vitamin deficiencies, and can impact hydration through its symptoms. It is vital that you consult with a healthcare professional for an accurate diagnosis. By providing a HMBT for an accurate diagnosis, healthcare professionals can tailor treatment to relieve symptoms, providing better outcomes for patients.
The Gastrolyzer® range by Bedfont® Scientific Limited
The Gastrolyzer® range of HMBT devices is designed to aid the diagnosis of various gastrointestinal conditions, such as SIBO and carbohydrate malabsorption.
The Gastro+™ is a portable, handheld device that measures hydrogen gas levels in exhaled breath. Breath testing can be performed with mouthpieces or by facemask, making it a perfect solution for infants and elderly patients who may struggle to hold their breath before exhaling.
The GastroCH4ECK® is a desktop HMBT device that measures hydrogen and methane gas levels in exhaled breath. Remote testing can be performed with the GastroCH4ECK® using breath bags for accurate, reliable results.
For more information on HMBT and how tools like the Gastrolyzer® are aiding gastrointestinal investigations, visit the educational portal here.
References
- SIBO Symptoms & Diagnosis | Digestive Health | Royal Bucks [Internet]. The Royal Buckinghamshire Hospital. 2025 [cited 2026 Jan 21]. Available from: https://www.royalbucks.co.uk/conditions-and-symptoms/small-intestinal-bacterial-overgrowth/
- Shah A, Thite P, Hansen T, Kendall BJ, Sanders DS, Morrison M, et al. Links between celiac disease and small intestinal bacterial overgrowth: A systematic review and meta‐analysis. Journal of Gastroenterology and Hepatology [Internet]. 2022 Oct 1;37(10):1844–52. Available from: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC9795979/
- Goździewska M, Łyszczarz A, Kaczoruk M, Kolarzyk E. Relationship between SIBO and other bowel diseases and a common eating pattern for them. Part III. Annals of Agricultural and Environmental Medicine. 2024 Sep 19;31(3):322–8.
- Hydrogen/Methane Breath Testing for SIBO and Malabsorption [Internet]. Bsg.org.uk. 2024. Available from: https://www.bsg.org.uk/clinical-resource/agip-protocol-for-hydrogen-methane-breath-testing
- Sahakian AB, Jee SR, Pimentel M. Methane and the Gastrointestinal Tract. Digestive Diseases and Sciences [Internet]. 2009 Oct 15;55(8):2135–43. Available from: http://image.sciencenet.cn/olddata/kexue.com.cn/upload/blog/file/2010/1/2010123203248875447.pdf
- Gastroadmin. Management of Small Intestinal Bacterial Overgrowth – SIBO [Internet]. London Gastroenterology Centre. 2019. Available from: https://www.gastrolondon.co.uk/management-of-small-intestinal-bacterial-overgrowth-sibo/
