SIBO

SIBO means too many bacteria in the small intestine, causing bloating, wind, diarrhoea and sometimes poor absorption. It’s real and treatable in people with clear risk factors. It’s also heavily overdiagnosed with unreliable breath tests, at considerable cost.

If an online quiz diagnoses you with SIBO and then sells you the herbs, that’s not a test. That’s a shop.

Who really gets it

• People who’ve had bowel or stomach surgery, especially loops or bypasses
• Slow gut movement: scleroderma, diabetes with nerve damage, intestinal pseudo-obstruction
• Very low stomach acid, older age, cirrhosis, some immune problems
• Long-term opioids or strong acid suppression may add to risk
• Its role in everyday IBS is debated

Symptoms

• Bloating, wind, tummy discomfort and diarrhoea
• In more severe cases: weight loss, low B12, iron or fat-soluble vitamins, fatty pale stools

See your GP soon for any of these: weight loss you can’t explain, vomiting that won’t settle, trouble swallowing, black or bloody stools, low iron or anaemia, a family history of bowel or stomach cancer, or new symptoms after 60.

Testing

• Breath tests (glucose or lactulose) are widely used but often wrong: false positives with fast gut transit, false negatives otherwise.
• The gold standard, sampling fluid from the small bowel, is rarely done outside research.
• In people with strong risk factors, doctors sometimes treat without a test.
• Also check for coeliac disease, IBD, pancreatic problems and bile acid diarrhoea, which cause similar symptoms.

What helps

Treat the cause where possible; antibiotics treat the overgrowth.

1. Step 1 · GP or specialistAntibiotics: rifaximin, or amoxicillin-clavulanate, metronidazole or doxycyclineA 1–2 week course.

   Works

   Relieves symptoms in many with true SIBO; rifaximin isn’t PBS-listed for SIBO in Australia, so it’s expensive

   Cost

   Low cost for older antibiotics; rifaximin costs hundreds privately

   How long

   1–2 weeks

   Watch for

   Recurrence is common, especially when the underlying cause stays.

2. Step 2 · Treat the causeReview medicines, treat motility problems, correct anatomy where possibleOpioids and acid suppression reviewed; prokinetics for slow motility.

   Works

   Reduces recurrence

   Cost

   Varies

   How long

   Ongoing

   Watch for

3. Step 3 · NutritionCorrect deficiencies: B12, iron, vitamin D and othersWith a dietitian if weight is falling.

   Works

   Essential when absorption is affected

   Cost

   Varies

   How long

   Ongoing

   Watch for

4. Step 4 · SpecialistRotating antibiotic courses for frequent relapseFor clear underlying causes like surgery or scleroderma.

   Works

   Helpful for selected people

   Cost

   Varies

   How long

   Long term

   Watch for

   Antibiotic resistance, C. difficile.

Costs are rough Australian prices and vary by pharmacy and provider. PBS co-payment: $25, or $7.70 with a concession card. Results are typical figures from trials, not promises.

Save your money

Popular, heavily marketed or often asked about, but the evidence is weak or says no.

• Repeated breath tests to “track” SIBOThey’re unreliable and don’t guide treatment well.
• Long-term restrictive “SIBO diets”Can harm nutrition and gut bacteria diversity. Short low-FODMAP trials with a dietitian are better evidenced for IBS.
• Herbal antimicrobial protocolsOne small study; quality and dosing vary. Not proven.
• Elemental dietsSome evidence, but very hard to tolerate and expensive. Specialist-guided only.

Helpful resources

• GESAPatient information on gut conditions. Free.

Evidence and more information

• Pimentel M et al. ACG clinical guideline: small intestinal bacterial overgrowth (2020)
• Rezaie A et al. Hydrogen and methane-based breath testing: North American consensus (2017)

Updated 14 November 2026. General education, not personal medical advice. Treatment depends on your situation, so talk to your GP or pharmacist.

maladywise.com/sibo/