SIBO occurs when bacteria normally found in the colon overgrow in the small intestine, where they ferment carbohydrates before they can be properly absorbed — producing gas, bloating, diarrhea, and sometimes malabsorption. It's associated with IBS and multiple GI and systemic conditions.

Glucose or lactulose breath testing — measuring exhaled hydrogen and methane produced by intestinal bacteria — is the most widely used diagnostic method. It's non-invasive but has limitations in accuracy. Small bowel aspiration and culture is more definitive but rarely performed outside specialized centers.

Risk factors include prior abdominal surgery, small bowel dysmotility, gastroparesis, IBS, celiac disease, Crohn's disease, hypothyroidism, chronic PPI use, and anatomical abnormalities. Identifying and addressing the underlying cause is important to prevent recurrence after treatment.

Recurrence is common — particularly when an underlying predisposing condition isn't addressed. Some patients require repeated treatment courses or rotating antibiotic strategies. Dietary approaches (low-FODMAP, specific carbohydrate diet) may reduce symptom burden between courses but don't eliminate the bacterial overgrowth.

Rifaximin — the most commonly prescribed antibiotic for SIBO — is generally very well tolerated due to minimal systemic absorption. GI symptoms are the most reported side effect. Herbal antimicrobial protocols are used by some patients — evidence is limited and tolerability varies. Elemental diet is effective but difficult to sustain. Small Intestinal Bacterial Overgrowth (SIBO) visit What to expect from a Small Intestinal Bacterial Overgrowth (SIBO) visit