SIBO: when “IBS” is not actually IBS
A 2020 meta-analysis put the overlap between IBS and SIBO at roughly 60 to 80%. The takeaway: most “irritable bowel” is actually small intestinal bacterial overgrowth that nobody tested for. Different problem, different protocol, very different outcome.
How IBS gets diagnosed today
Most gastroenterology workups for chronic bloating include a colonoscopy (to rule out IBD), a CBC, a CMP, and sometimes a stool test for parasites and pathogens. If nothing structural shows up, the diagnosis is IBS by exclusion. The treatment is usually a low-FODMAP diet, a fiber supplement, and an antispasmodic. Sometimes that helps. Often it does not.
What SIBO actually is
Small intestinal bacterial overgrowth means too many bacteria living in the small intestine, where the bacterial count is supposed to be low. The bacteria ferment carbohydrates, produce gas (hydrogen, methane, hydrogen sulfide), and cause the cluster of symptoms most people call IBS:
- Bloating that gets worse as the day goes on
- Post-meal abdominal pain
- Constipation (methane-dominant SIBO) or diarrhea (hydrogen-dominant)
- Reflux and belching
- Brain fog after meals, especially carb-heavy ones
- Skin issues (rosacea, eczema, adult acne) that flare with the gut
The breath test
SIBO is diagnosed with a lactulose breath test. The patient drinks a measured carbohydrate solution and breathes into collection tubes every 15 to 20 minutes for three hours. The lab measures hydrogen and methane production over time. A positive test shows the gases spiking before the carbohydrate has time to reach the colon – i.e., the bacteria fermenting it are in the small intestine, where they should not be.
The test costs roughly $180 to $230 cash pay. We almost always pair it with the GI-MAP DNA stool analysis to see what else is going on (pathogens, dysbiosis, candida, intestinal inflammation markers).
The protocol
Treatment is targeted. Hydrogen SIBO usually responds to rifaximin (a non-absorbed antibiotic) or to a strict herbal protocol (berberine, oregano oil, neem). Methane SIBO needs rifaximin plus neomycin or specific herbal pairs. Diet adjustments are temporary, not lifelong.
Two-to-four weeks of targeted treatment plus a structured re-introduction phase clears most cases. The recurrence rate is real (~30 to 40%), which is why we screen for the underlying drivers: poor motility, low stomach acid, ileocecal valve dysfunction, structural issues, chronic stress. The recurrences come from the same upstream cause.
If you have been “IBS” for years
If your previous workup did not include a SIBO breath test, the diagnosis is incomplete. The breath test takes one morning. The answer changes the entire treatment plan. See how the gut workup runs at Copper Sage.