The gold-standard test for SIBO is a hydrogen/methane breath test. You consume a sugar solution (lactulose or glucose) and breath samples are taken at regular intervals over 2–3 hours. If bacteria in the small intestine ferment the sugar and produce hydrogen and/or methane gas, this will be detected in the breath. The pattern and timing of the gas response indicates both the presence and type of SIBO.

Clinically, the symptoms I look for that suggest SIBO include: significant bloating that worsens throughout the day and after meals; excessive gas or belching; alternating diarrhoea and constipation; brain fog, fatigue, and nutritional deficiencies disproportionate to diet; and IBS symptoms that haven't responded to standard dietary management. A history of food poisoning or a gut infection that marked the onset of gut symptoms is also a strong clinical indicator.

I can arrange breath testing for clients as part of an assessment. If you recognise your symptoms in this description, a breath test can give us a clear diagnostic picture to work from. Book a free Strategy Session to discuss testing options: vibrantnutrition.com.au.

A SIBO flare-up typically involves a dramatic increase in digestive symptoms, often appearing or worsening shortly after eating. The hallmark symptom is intense bloating — often severe enough to make clothing uncomfortable and visible to others — accompanied by abdominal pain or cramping. Excessive gas, belching, diarrhoea, constipation (particularly in methane-dominant SIBO), or a combination of both are common.

Unlike IBS flares, which can be more generalised, SIBO flares often have a clear timing pattern: symptoms tend to worsen throughout the day and after meals, particularly meals containing fermentable carbohydrates. Fatigue, brain fog, and nausea during flares are also frequently reported by my clients.

If you're experiencing regular flares despite dietary management, it may indicate that the underlying SIBO hasn't been fully treated or has recurred. Recurrence is common with SIBO — this is why addressing the root cause and implementing motility support is as important as the treatment itself.

SIBO doesn't occur randomly — it develops when the body's defence mechanisms against bacterial overgrowth in the small intestine are impaired. The most fundamental trigger is poor gut motility, specifically dysfunction of the Migrating Motor Complex (MMC) — the housekeeping wave that sweeps bacteria through the small intestine between meals. When the MMC is impaired (often following a gut infection or injury), bacteria accumulate.

Common underlying triggers include a history of food poisoning or gastroenteritis (post-infectious IBS/SIBO is well-documented), low stomach acid (which allows bacteria from the mouth and food to survive into the small intestine), structural issues like adhesions or diverticula, hypothyroidism, diabetes, and the regular use of medications like proton pump inhibitors or opioids that slow gut motility.

Understanding your personal underlying trigger is essential for preventing SIBO from recurring — treating the overgrowth without addressing what caused it means it's highly likely to come back. This is a key focus of the work I do with SIBO clients.

Changes in bowel habits are often one of the most distressing aspects of SIBO, and the pattern depends on which type you have. Hydrogen-dominant SIBO tends to be associated with diarrhoea — loose, frequent, urgent stools, often pale or floating (indicating fat malabsorption). Methane-dominant SIBO (IMO) is more typically associated with constipation, slow transit, and hard, difficult-to-pass stools.

Floating, pale, foul-smelling stools are a sign of fat malabsorption — something that occurs when SIBO interferes with bile acids and digestive enzymes in the small intestine. Undigested food in stools and significant bloating alongside bowel changes are also common. These aren't just uncomfortable — they indicate your body isn't absorbing nutrients properly, which has wider health implications.

If you've noticed these kinds of changes, it's worth proper investigation. SIBO can be accurately tested using a breath test, and the results guide the treatment approach.