Breath Test Helps Diagnose Bacterial Overgrowth in IBS Patients
- Authors
- A Dahlgren, P Grybäck, H Jacobsson, P M Hellström
- Journal
- BMC Gastroenterology
- Year
- 2026
- DOI
- 10.1186/s12876-026-04782-w
- Study Type
- Human
- Outcome
- Neutral
- Peer Reviewed
- Yes
- Country
- Sweden
- Health Condition
- Irritable Bowel Syndrome (IBS)
- Body System
- Gastrointestinal
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
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 breath test (LHBT) in IBS. As a secondary aim, we optimized the diagnostic time frame for the small bowel. Methods: LHBT was performed on 503 subjects who met the inclusion criteria. After excluding non-hydrogen producers, the remaining 462 subjects were 92 healthy individuals and 370 IBS patients. Peak hydrogen levels were summarized as median values with interquartile range. Results: At the 80-min orocecal cut-off, healthy subjects showed a peak hydrogen of 8(4–11) ppm compared with 10(4–29) ppm in the overall IBS group (p <0.0001). Using ≥20 ppm cut-off, sensitivity was 38% and specificity 77%. Peak hydrogen was highest in IBS-D (24(9-40) ppm; p <0.0001), intermediate in IBS-M (7(4-14) ppm), and lowest in IBS-C (7(4-10) ppm), showing sensitivities of 61%, 23%, and 10%, respectively, with specificity 77%.After antibiotics, IBS patients with low hydrogen were unchanged, whereas most with high hydrogen reduced their hydrogen levels (p <0.01). Conclusion: Using a cut-off level of ≥20 ppm during the first 80 minutes, LHBT can diagnose SIBO in people with IBS showing high breath hydrogen, as compared with those having low breath hydrogen. Hence, SIBO-positive patients can be separated from SIBO-negative IBS patients. To this end, a majority of SIBO-positive subjects respond to antibiotic treatment.