SIBO vs IBS: How to Tell the Difference (And Why It Matters)

SIBO vs IBS: How to Tell the Difference (And Why It Matters)

By Dr. Onikepe Adegbola, MD PhD — Johns Hopkins-trained physician-scientist

Up to 78% of IBS patients actually have SIBO (small intestinal bacterial overgrowth). This means most "IBS" diagnoses may be missing the underlying cause. Understanding the difference changes your treatment approach entirely.

Key Takeaways

• IBS is a symptom-based diagnosis (Rome IV criteria) — it tells you WHAT, not WHY
• SIBO is a measurable overgrowth of bacteria in the small intestine — it tells you WHY
• SIBO is diagnosed by lactulose or glucose breath test — IBS has no specific test
• SIBO treatment is antimicrobial (rifaximin, herbal antimicrobials); IBS treatment is symptom management
• Both benefit from digestive enzymes and probiotics

Comparison

The Overlap

Many patients have both. SIBO causes IBS-type symptoms, and having IBS (specifically slow motility) makes you more susceptible to developing SIBO. Treatment approach:

1. Test for SIBO first: If positive, treat the overgrowth
2. During treatment: Low FODMAP diet + digestive enzymes to reduce bacterial substrate
3. After treatment: Rebuild with probiotics + psyllium fiber
4. Prevention: Prokinetic agent + continued enzyme/probiotic support

See our SIBO treatment guide and Berberine vs Rifaximin comparison.

This article is educational only. SIBO testing and treatment requires medical supervision.