Your small intestine is supposed to have relatively few bacteria living in it. The bulk of your gut bacteria live much further down, in the large intestine. When bacteria start overgrowing in the small intestine — where they should not be — the condition is called small intestinal bacterial overgrowth, or SIBO.
Why the small intestine is normally kept clean
Several protective mechanisms work together. Stomach acid kills most bacteria before they travel further down. During fasting periods, your gut runs a self-cleaning cycle that sweeps bacteria downward. A valve between the small and large intestine prevents bacteria from backing up. When any of these systems are disrupted, bacteria can overgrow in the wrong place.
Common triggers include impaired gut motility (from conditions like diabetes, an underactive thyroid, or past gut infections), reduced stomach acid (sometimes from long-term use of acid-suppressing medications), previous abdominal surgery, or no identifiable cause.
What SIBO feels like
The symptoms overlap heavily with IBS, which is part of why it often goes undiagnosed for years. Bloating is the most consistent symptom — usually appearing within an hour or two of eating, often worse after carbohydrate-heavy meals, sometimes severe enough to cause visible abdominal distension. Excess gas, belching, cramping, irregular bowel habits, and fatigue are all common.
The key distinguishing feature from IBS: in SIBO, symptoms tend to appear quickly after eating almost any meal, not just after specific trigger foods.
How it is diagnosed and treated
A breath test is the standard diagnostic tool. You drink a sugar solution, bacteria in the small intestine ferment it, and gases appear in your breath in a pattern that indicates overgrowth.
Treatment typically involves a specific antibiotic that works in the gut without being absorbed into the bloodstream. For some people, herbal antimicrobial protocols are an alternative worth discussing with a practitioner.
The most important piece for long-term recovery: addressing the underlying cause. If the motility problem driving SIBO is not fixed, it comes back. Eating with consistent gaps between meals — around four to five hours during the day — and not eating late into the night gives the small intestine the fasting time it needs to run its cleaning cycle and keep bacteria in the right place.
Your next steps: If you have persistent bloating that appears quickly after almost any meal, irregular digestion, and fatigue that has not responded to dietary changes, ask your GP or gastroenterologist about SIBO breath testing. Do not self-treat without a diagnosis — the treatment differs depending on the type of SIBO, and getting it wrong can make things worse. If SIBO is confirmed, work with a practitioner who understands both the treatment and the post-treatment support needed to prevent recurrence.
This content is for educational purposes only and is not a substitute for professional medical advice.