A patient’s story
Emma, a 38-year-old professional working in central London, came to see me after months of persistent bloating. Each morning she felt relatively comfortable, but by early afternoon her abdomen became tight, uncomfortable, and visibly distended. She had already been told she had IBS, tried eliminating foods, followed dietary advice, and adjusted her lifestyle, yet nothing had changed.
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What frustrated her most was being reassured that her tests were “normal” while her symptoms clearly were not. This is a situation I see regularly in clinic. If you are experiencing daily bloating that has never been properly explained, there is often an underlying cause that has simply not been identified yet. One of the most common is small intestinal bacterial overgrowth, commonly known as SIBO.
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SIBO occurs when excessive amounts of bacteria are present in the small intestine, an area that normally contains relatively few bacteria compared to the large bowel. These bacteria ferment food earlier than they should, producing gas that leads to bloating, discomfort, and changes in bowel habits.
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Clinically, SIBO is not a vague or alternative diagnosis. It is a well-recognised gastrointestinal condition that can be objectively tested for and explained by gut physiology.
What is SIBO?
SIBO occurs when excessive amounts of bacteria are present in the small intestine, an area that normally contains relatively few bacteria compared to the large bowel. When bacteria are present where they should not be, they begin fermenting food too early in the digestive process.
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This fermentation produces gas inside the small intestine, leading to bloating, discomfort, and changes in bowel habits.
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From a clinical perspective, SIBO is not a vague or alternative diagnosis. It is a well-recognised gastrointestinal condition, supported by gut physiology and validated testing methods. When identified correctly, it provides a clear explanation for symptoms that are often otherwise labelled as functional.
SIBO vs IBS and functional bloating
This distinction is crucial.
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You may have been told you have IBS. IBS is a symptom-based diagnosis. It describes a pattern of abdominal pain, bloating, and bowel disturbance, but it does not explain why those symptoms are happening.
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Functional bloating is similar. It refers to bloating without an identifiable structural cause on routine testing.
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SIBO is different. It is a specific diagnosis with a measurable cause. Rather than labelling symptoms, it explains their origin.
In my clinical practice, I frequently see patients who were previously diagnosed with IBS, but further assessment and breath testing revealed underlying SIBO. This does not mean the IBS diagnosis was wrong, but rather incomplete.
Patients with SIBO often report a combination of symptoms, including:
Persistent bloating that worsens through the day
Excessive gas or belching
Abdominal discomfort or cramping
Diarrhoea, constipation, or alternating bowel habits
Symptoms that do not respond to standard IBS advice
If bloating is your dominant and most troubling symptom, SIBO should be considered.
Symptoms that raise suspicion for SIBO
Patients with SIBO often report a combination of:
Persistent bloating that worsens through the day
Excessive gas or belching
Abdominal discomfort or cramping
Diarrhoea, constipation, or alternating bowel habits
Symptoms that do not respond to standard IBS advice
If bloating is your dominant and most troubling symptom, SIBO should be considered as part of a structured assessment.
How SIBO is diagnosed at LSDC
At LSDC in central London, I actively test for SIBO using validated breath testing. This test measures hydrogen and methane gases produced by bacteria after ingestion of a specific substrate.
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Testing matters. Without objective assessment, SIBO can be missed, mislabelled, or repeatedly treated as IBS without addressing the underlying issue.
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Breath testing allows us to:
Confirm or exclude SIBO
Identify the gas pattern involved
Build an appropriate diagnostic plan
This approach replaces guesswork with clarity.
When to seek specialist assessment
You should consider specialist review if:
Bloating is persistent and unexplained
Dietary changes have not helped
IBS treatments have failed
Symptoms are affecting your quality of life
Early assessment can prevent months or years of ongoing symptoms and uncertainty.
Speak to a gastroenterologist about SIBO
If you are experiencing ongoing bloating and suspect SIBO may be contributing, the next step is a clinical consultation and appropriate testing, rather than guessing or self-treating.
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At LSDC, I see patients with complex digestive symptoms every day and provide structured assessment based on evidence and experience.
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To discuss your symptoms and arrange testing, book an appointment through our online form.