SIBO Breath Test (Lactulose): Non-Invasive Assessment of Small Intestine Bacterial Overgrowth

The Lactulose SIBO Breath Test is a three-hour, non-invasive diagnostic tool that measures hydrogen (H₂) and methane (CH₄) gas levels in the breath following ingestion of lactulose. It provides valuable insight into the function and microbial balance of both the small and large intestines.

This test is primarily used to detect Small Intestinal Bacterial Overgrowth (SIBO) and Intestinal Methanogen Overgrowth (IMO), both of which are associated with a range of gastrointestinal symptoms and systemic conditions.

What the SIBO Breath Test Measures

• Hydrogen (H₂) and methane (CH₄) gas production following lactulose ingestion
• Carbon dioxide (CO₂) levels to verify sample viability
• Early rises in gas production may indicate SIBO or IMO
• Later peaks in gas levels may reflect colonic fermentation or excessive methanogenesis

This testing method enables clinicians to distinguish between different forms of gut dysbiosis and tailor treatment accordingly.

Who Should Consider This Test

The test is appropriate for individuals presenting with:

• Unresolved irritable bowel syndrome (IBS)-like symptoms
• Chronic bloating, abdominal discomfort, or flatulence
• Alternating bowel habits (constipation, diarrhoea, or both)
• A history of gastroenteritis, antibiotic use, or food poisoning
• Suspected methane-dominant constipation or mixed-type SIBO

Important Note:
This test is not suitable for individuals with diabetes, due to the impact of lactulose on blood sugar regulation.

How the Test Works

Patients ingest a standard dose of lactulose, a non-absorbable sugar, and provide breath samples at regular intervals over a 3-hour period. The gases measured in these samples reflect bacterial activity in the gastrointestinal tract. An abnormal pattern of gas elevation can indicate the presence of fermenting bacteria or methanogens in the small intestine, where they are not typically found in high numbers.

Turnaround Time

Laboratory processing typically takes 3 business days, excluding courier transit.

What to Expect

Following testing, your clinician at The Long COVID Clinic will interpret the results and, if appropriate, initiate a personalised treatment plan that may include antimicrobial therapies, dietary changes, and microbiome support.

To learn more or to arrange a SIBO Breath Test, please contact The Long COVID Clinic.