Enter the hydrogen and methane gas levels from the report to visualize the gas-dynamic profile.
Guidelines & Evidence
Clinical Details
Section 1
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.
Section 2
Formula & Logic
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.
Section 3
Pearls/Pitfalls
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.
Clinical Pearls
Methane (CH4) levels correlate directly with the severity of constipation
Antibiotics, bismuth, and probiotics must be stopped 4 weeks prior to testing
The "Baseline" must be low (< 10 H2); a high baseline suggests an inadequate low-fiber "Prep Diet"
