Small intestinal bacterial overgrowth: SIBO
Content date: 14 November 2026
Bloating alone does not establish SIBO. Assessment depends on context and suitable testing; treatment addresses causes and nutrition, not repeated antibiotics alone.
Your next step
Bring your surgical history, medicines, previous antibiotics and full breath-test report if available.
Get urgent help: Severe pain, possible obstruction, major bleeding, fainting or severe dehydration needs urgent assessment.
What is SIBO?
- Changes in small-bowel bacterial numbers or composition can become clinically important after some operations or with motility disorders. Possible symptoms include bloating, discomfort, diarrhoea and occasionally nutritional deficiencies; these are shared by many other conditions.
Is it the same as IBS?
- No. IBS is a disorder of gut–brain interaction; SIBO is a separate consideration in selected circumstances. Neither bloating nor improvement with an antibiotic proves SIBO, and testing is not appropriate for every person with IBS.
Tests and their limitations
- A clinician may use a breath test after a test substrate with specific preparation. Transit speed and preparation affect results, and false results occur. Interpret testing with history and symptoms; other investigations may suit selected cases.
- Methane elevation, sometimes associated with constipation, is termed intestinal methanogen overgrowth and is not identical to bacterial overgrowth. Calprotectin and commercial microbiome tests do not establish SIBO.
What does treatment involve?
- Treatment addresses modifiable causes and nutritional deficiencies and may include a selected antibiotic. Persistent underlying problems can lead to recurrence, requiring reassessment rather than automatic repeat courses.
- Food adjustments may relieve symptoms but do not prove the diagnosis or guarantee eradication. Avoid prolonged restrictive diets and “gut cleansing” mixtures; review supplements with your team.
When to get help
Severe pain, possible obstruction, major bleeding, fainting or severe dehydration needs urgent assessment.
Weight loss, greasy stools, anaemia or persistent diarrhoea should not automatically be attributed to IBS or SIBO.
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