Breath Test Helps Diagnose Bacterial Overgrowth in IBS Patients
Extended hydrogen breath test analysis for optimized diagnosis of SIBO-positive IBS patients
Research hubs: Digestive System
- Evidence type
- Observational study · Human study
- Authors
- A Dahlgren, P Grybäck, H Jacobsson, PM Hellström
- Journal
- BMC Gastroenterology
- Year
- 2026
- PMID
- 41942940
- Study Type
- Human
- Participants
- 462
- Delivery
- Gas
- H₂ concentration
- ≥20 ppm
- Outcome
- Neutral
- Peer Reviewed
- Yes
- Cited by
- 0 (OpenAlex, as of November 2026)
- Country
- Sweden
TL;DR
In IBS patients, a lactulose hydrogen breath test threshold of ≥20 ppm within the first 80 minutes helped identify likely SIBO, especially in IBS-D, and high-hydrogen patients often showed reduced breath hydrogen after antibiotics.
Key Finding
A hydrogen breath test threshold of ≥20 ppm at 80 minutes can effectively distinguish SIBO-positive from SIBO-negative IBS patients, with the highest diagnostic accuracy (61% sensitivity) in patients with diarrhea-dominant IBS.
Summary
This study tested 462 people (92 healthy and 370 with irritable bowel syndrome, or IBS) using a hydrogen breath test to detect small intestinal bacterial overgrowth (SIBO—when too many bacteria grow in the small intestine). Researchers found that a hydrogen level of 20 parts per million or higher at 80 minutes after drinking a test solution could reliably identify SIBO in IBS patients, especially those with diarrhea-dominant IBS. Most patients with high hydrogen levels improved after taking antibiotics, suggesting the test could identify people who might benefit from treatment.
Practical Takeaway
This study suggests that hydrogen breath testing may help identify which IBS patients have bacterial overgrowth that could respond to antibiotics. However, this research focuses on diagnostic testing rather than hydrogen water consumption, so it does not directly inform whether drinking hydrogen water would benefit IBS or SIBO. Anyone considering hydrogen water or breath testing should consult their healthcare provider.
Abstract (excerpt)
Abstract Background Small intestinal bacterial overgrowth (SIBO) is suggested in irritable bowel syndrome (IBS). Optimal hydrogen levels and time frame for diagnosing SIBO are still under discussion. Our primary aim was to consolidate a discriminating threshold for a positive lactulose hydrogen…