SIBO and bloating

Small intestinal bacterial overgrowth, known as SIBO, is a condition where excess bacteria build up in the small intestine. It is a recognised cause of persistent bloating, abdominal discomfort and changes in bowel habits. Understanding both the underlying cause and the symptoms is important, as effective treatment often needs a combined approach.

What is SIBO and why does it cause bloating?

The small intestine normally contains relatively low levels of bacteria. Its main job is to digest and absorb nutrients. When bacteria grow in higher numbers than expected, they interfere with digestion and produce gas. This often leads to bloating, distension, burping, wind and discomfort after eating.

Patients may also experience diarrhoea, constipation or a mixture of both. Symptoms can fluctuate, which sometimes makes the condition difficult to identify without specialist assessment.

What causes SIBO to develop?

SIBO has several possible causes. Anything that slows down the movement of food and waste through the gut can contribute, as this allows bacteria to multiply. Conditions such as irritable bowel syndrome, coeliac disease, diabetes, previous abdominal surgery or structural problems in the gut can make SIBO more likely.

Certain medications, including long-term acid suppression, can also affect the balance of bacteria. A specialist assessment helps pinpoint the most likely cause so that treatment can be tailored.

What symptoms suggest SIBO might be present?

SIBO symptoms can include:

Abdominal bloating, often worse after eating
Feeling full quickly, even after small meals
Excessive gas or burping
Diarrhoea, constipation or alternating bowel habits
Abdominal pain or cramping
Unexplained fatigue, due to poor nutrient absorption
Symptoms that improve after antibiotics, which is a helpful clinical clue

How is SIBO diagnosed?

A hydrogen or methane breath test is commonly used. This measures the gases produced after drinking a sugar solution, which can indicate the presence of excess bacteria. In some cases, diagnosis is made based on symptoms and response to treatment, especially when breath testing is not suitable.

Blood tests, stool tests and imaging may also be recommended to identify underlying conditions that could contribute to SIBO.

How is SIBO treated?

Treatment has two main goals: clearing the excess bacteria and addressing the cause so symptoms do not return. Antibiotics are often used to reduce bacterial levels and can provide quick relief from bloating and discomfort.

Dietary changes may also help. Some patients benefit from reducing fermentable carbohydrates that feed gut bacteria, although strict diets are not always necessary. Targeted nutritional advice ensures patients avoid unnecessary restrictions.

Managing underlying conditions is important. For example, improving gut motility, treating coeliac disease or adjusting certain medications can support long-term control.

What can patients expect in the long term?

SIBO can recur, especially if the underlying cause remains. Ongoing management may involve gentle pro-motility treatments, periodic follow-up and support from a gastroenterology specialist or dietitian. With the right approach, many patients experience lasting improvement in bloating, comfort and digestive health.

A personalised plan that treats both the cause and the symptoms gives the best chance of reducing flare-ups and restoring day-to-day wellbeing.