Breath Matrix • SIBO/IMO Interpretation
Enter the hydrogen and methane gas levels from the report to visualize the gas-dynamic profile.
Guidelines & Evidence
Verified
Last Review: 2026-07-17
When to Use
When to Use
Investigation of chronic bloating, gas, and diarrhea (suspected SIBO)
Evaluation of "IBS-overlap" patients who fail to respond to standard diet
Screening for Intestinal Methanogen Overgrowth (IMO) in chronic constipation
Assay Selection
The North American Consensus (2017) recommends the use of Glucose or Lactulose as the substrate. Simultaneous measurement of Hydrogen (H2) and Methane (CH4) is mandatory.
How it Works
Positive Diagnostic Thresholds
| Hydrogen (H2) | A rise of ≥ 20 ppm from baseline within 90 minutes |
| Methane (CH4) | A concentration of ≥ 10 ppm at ANY point during the test |
| Combined | Rise of H2 and CH4 combined (Non-standard but sometimes used) |
Intestinal Methanogen Overgrowth (IMO)
Methane production is now classified as IMO rather than "Methane-SIBO" because methanogens are archaea (not bacteria) and can reside in the colon as well as the small bowel.
Clinical Pearls
Lactulose vs. Glucose
Glucose is highly specific but less sensitive because it is absorbed in the proximal jejunum (missing distal SIBO). Lactulose is not absorbed, reaching the ileum, but it can produce false positives in patients with "Rapid Transit." Ideally, both should be considered alongside clinical duration.
The "Flatline" Result
A "flatline" result (0 ppm across the board) may represent "Hydrogen Sulfide (H2S) SIBO," where H2S-producing bacteria consume the hydrogen produced by others. This is not captured on standard 2-gas machines.
Next Steps
Management Action
01
H2 Positive: Rifaximin (550mg TID) for 14 days.
02
CH4 Positive (IMO): Rifaximin + Neomycin (or Metronidazole) for 14 days.
03
Negative: Look for other causes (EPI, Celiac, Sucrose malabsorption).
The Evidence
North American Consensus
Hydrogen and methane-based breath testing in gastrointestinal disorders: The North American Consensus.
Rezaie A et al. • American Journal of Gastroenterology. 2017;112(5):775-784. The definitive modern protocol for breath testing.
View Source• . ;
Last Comprehensive Review: 2026-07-17