SIBO, IMO, and Why the Difference Matters

Small intestinal bacterial overgrowth and intestinal methanogen overgrowth are often grouped together, but methane is produced by archaea rather than bacteria and the symptom patterns can differ.

What Breath Testing Measures

Breath testing tracks hydrogen and methane after a test substrate. Results must be interpreted with preparation quality, symptoms, transit time, and clinical history.

Key Patterns to Understand

Hydrogen Patterns

Higher hydrogen is often associated with diarrhea or faster transit, although symptoms are not perfectly predictable.

Methane Patterns

Methane is strongly associated with slower intestinal transit and constipation, which is why the term IMO can be more accurate.

Why Recurrence Happens

Motility, anatomy, medications, constipation, adhesions, and underlying disease can matter as much as the initial antimicrobial strategy.

What a Thoughtful Evaluation Includes

Testing is not necessary for every person with bloating. A thoughtful evaluation also considers celiac disease, pelvic-floor dysfunction, pancreatic issues, infection, and inflammatory disease.

A Functional Medicine Perspective

A root-cause approach does not assume one symptom has one universal cause. It looks at the timing of symptoms, cycle patterns, stress, nutrition, medications, relevant laboratory findings, and the way multiple body systems communicate.

The Bottom Line

The label should guide—not replace—clinical reasoning. Treatment and prevention depend on the gas pattern and the underlying reason overgrowth developed.