SIBO (small intestinal bacterial overgrowth)
Reviewed by Dr. Nikita Dinger, Founder & CEO, BioMeBar. Last reviewed 7 October 2026.
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What it is
The small intestine normally holds far fewer bacteria than the colon. Small intestinal bacterial overgrowth, or SIBO, is a diagnosis made when there are too many bacteria in that upper stretch, or when bacteria that usually live lower down have moved up. Their fermentation of food produces gas early in the digestive path, which can cause symptoms.
It is a topic where opinions among clinicians differ. Testing, interpretation and management are debated, and it has become something of an internet catch-all for bloating. A fair summary is that SIBO is real, it is probably over-suspected, and it should be diagnosed by a doctor.
In India, the discussion is complicated further by high rates of previous gut infection, widespread use of acid-suppressing tablets bought over the counter and diets rich in fermentable carbohydrates. All of these can produce SIBO-like symptoms without overgrowth, so it is sensible to look at the wider picture first.
Common symptoms
- Bloating, often within an hour or two of eating
- Gas, belching and abdominal discomfort
- Diarrhoea, constipation or alternating patterns
- Loose, greasy stools and weight loss in more severe cases
- Nutrient deficiencies, particularly vitamin B12 and sometimes iron or fat-soluble vitamins
These overlap strongly with IBS and with ordinary bloating, which is why testing and clinical judgement both matter.
How gut bacteria may be involved
Several factors normally keep bacterial numbers low in the small intestine: stomach acid, regular wave-like movements that sweep the gut clean, bile, and the valve between small and large intestine. If any of these is disturbed, overgrowth becomes more likely. Examples include long-term acid-suppressing medicines, previous abdominal surgery, strictures, diabetes, scleroderma, Crohn’s disease and slow gut movement.
The standard tests are hydrogen and methane breath tests after a sugar drink. They are imperfect: results can be affected by how fast sugar travels through the gut, by preparation diet, and by differing thresholds between labs. A positive result does not always mean overgrowth, and a negative one does not always rule it out. Stool microbiome tests cannot diagnose SIBO because they sample the colon.
When SIBO is diagnosed, doctors often prescribe a course of prescribed antibiotics and look for the underlying reason. Recurrence is common if that reason remains.
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Diet and everyday habits
Long restrictive diets are not recommended for SIBO, and there is no firm evidence for any single regimen. Practical measures during a medically supervised plan may include the following.
- Regular meals with gaps of about three to four hours, which gives the gut time to sweep between meals
- Smaller portions of high-FODMAP foods such as onion, garlic, wheat in large amounts, rajma, chana and sweet fruits, with reintroduction afterwards
- Easier choices in the meantime: rice, idli, khichdi, moong dal, lauki, carrot, pumpkin and curd if tolerated
- Protein and enough calories if you have lost weight
- Do not make long restrictive lists on your own. A dietitian can keep nutrition on track
Bile, enzymes and motility all depend on a steady eating pattern. Avoiding constant grazing, and allowing a gap overnight of at least ten to twelve hours, supports the natural cleaning waves of the small bowel that run between meals.
When to see a doctor first
- Unplanned weight loss, anaemia or persistent greasy stools
- Numbness, tingling or marked fatigue, which can reflect low B12
- Blood in the stool, fever or severe pain
- Symptoms after abdominal surgery, or in the context of diabetes, Crohn’s disease or long-term acid medicines
- Repeated courses of antibiotics from different sources with symptoms that keep returning
How BioMeBar approaches it
We ask whether you have had a diagnosis and which tests were done. If you have, we work around your doctor’s plan. If you have not, we recommend a medical review before assuming SIBO. Your gut profile and symptoms then inform a personalised synbiotic match, with food and lifestyle guidance and check-ins.
We do not diagnose, treat or cure SIBO and do not suggest synbiotics as a substitute for medical care.
Because SIBO is often linked to an underlying reason, our role is a supportive one around your doctor’s plan, with a focus on routine, nutrition and symptom tracking.
Common questions
Can probiotics cause SIBO?
This has been proposed in small studies of people with brain fogginess and bloating, but evidence is limited and debated. Anyone worried should discuss their product with their doctor.
Why does SIBO come back?
Often because the underlying reason, such as slow motility or anatomy, has not changed. This is why doctors look for a cause and not only the overgrowth.
Is a breath test enough to diagnose it?
It is useful but imperfect. Doctors weigh the result alongside your symptoms and history.
Do I need to avoid all fibre?
No. Fibre keeps the colon community supplied and supports regular bowels. During a supervised plan, doctors may ask you to adjust the type and amount, and then rebuild.
Sources
- ACG Clinical Guideline: Small Intestinal Bacterial Overgrowth (2020)
- North American Consensus on Breath Testing for Small Intestinal Bacterial Overgrowth and carbohydrate malabsorption (2017)
- Rome IV diagnostic criteria for functional gastrointestinal disorders (Rome Foundation)
- ICMR-NIN Dietary Guidelines for Indians
Talk to us
If you would like to know whether BioMeBar can support you, message us on WhatsApp. Tell us your symptoms and your pincode and we will take it from there. Not sure where to start? Take the free gut assessment, which takes about three minutes.
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BioMeBar provides nutrition and gut health guidance and does not replace medical care. See a doctor for severe, persistent or worrying symptoms.