SIBO (Small Intestinal Bacterial Overgrowth)

Digestive Health & Nutrition Care
Written By Jennifer Tang

Overview

Small intestinal bacterial overgrowth, or SIBO, describes an excessive number of bacteria in the small intestine associated with gastrointestinal symptoms. It is more likely to develop when the normal movement or anatomy of the digestive tract is disrupted, allowing bacteria to accumulate where they would not normally be present in large numbers.¹˒²

At Tangible Health, we take an individualized approach to suspected or diagnosed SIBO by looking at your symptom pattern, bowel habits, previous digestive conditions or surgeries, medications, intestinal motility, nutrition, and previous testing or treatment. Because symptoms such as bloating, gas, abdominal pain, diarrhea, and constipation overlap with many other digestive conditions, care starts with determining whether SIBO is actually a likely explanation rather than assuming it is the cause of every digestive symptom.³˒⁴

What Is SIBO?

The small intestine naturally contains bacteria, but normally in different concentrations and communities than the large intestine. SIBO occurs when bacterial numbers or composition in the small bowel become excessive enough to contribute to digestive symptoms or impaired nutrient absorption.¹˒²

SIBO is particularly well recognized in situations that interfere with the normal clearance of intestinal contents, such as certain structural abnormalities, previous gastrointestinal surgery, or disorders that significantly slow intestinal movement. In more severe cases, excessive bacterial activity can interfere with digestion and nutrient absorption, contributing to deficiencies or weight loss.¹˒⁵

The role of SIBO in people with IBS, bloating, or other disorders of gut-brain interaction is more controversial. These symptoms can occur with or without SIBO, and current research has raised concerns about overdiagnosis based on breath testing alone.³˒⁴

Common Symptoms of SIBO

Symptoms associated with SIBO may include:¹˒⁵˒⁶

  • Bloating or abdominal distension

  • Excess gas

  • Abdominal discomfort or pain

  • Diarrhea

  • Changes in bowel habits

  • Nausea

  • Uncomfortable fullness after meals

  • Fatigue

More significant bacterial overgrowth can interfere with nutrient absorption and may contribute to:

  • Unintentional weight loss

  • Vitamin B12 or other nutrient deficiencies

  • Fat malabsorption

  • Malnutrition in more severe cases¹˒⁵

These symptoms are not specific to SIBO. Bloating, abdominal pain, diarrhea, constipation, and gas can also occur with IBS, celiac disease, food intolerances, inflammatory bowel disease, and several other digestive conditions.³˒⁴

Causes & Contributing Factors

SIBO usually develops when one or more normal mechanisms that regulate bacteria in the small intestine are disrupted.

Slowed Intestinal Motility
Regular muscular contractions help move food and bacteria through the small intestine. Conditions or medications that significantly slow intestinal movement can increase the risk of bacterial accumulation.¹˒²

Structural Changes & Previous Surgery
Certain gastrointestinal surgeries, strictures, diverticula of the small intestine, fistulas, or other structural changes can create areas where intestinal contents stagnate and bacteria can accumulate.¹˒⁵

Underlying Medical Conditions
Conditions affecting intestinal movement or digestion, including some neurological, connective-tissue, metabolic, and gastrointestinal disorders, may increase SIBO risk. Diabetes and certain thyroid conditions may also affect intestinal motility in some people.¹

Medications
Medications that slow intestinal movement, particularly opioids, can increase SIBO risk in susceptible individuals. Medication history is therefore an important part of assessment.¹

IBS & Other Digestive Symptoms
SIBO is sometimes diagnosed in people with IBS, especially when bloating or altered bowel habits are prominent. However, the relationship between SIBO and IBS remains debated, and a positive breath test does not necessarily prove that bacterial overgrowth is the cause of someone’s symptoms.³˒⁴

SIBO vs. Intestinal Methanogen Overgrowth (IMO)

People sometimes hear terms such as “hydrogen SIBO” and “methane SIBO.” More accurately, elevated methane is now generally referred to as intestinal methanogen overgrowth (IMO). Methane is produced primarily by microorganisms called methanogens, which are archaea rather than bacteria. They can be present in both the small and large intestine, so methane overgrowth is not technically the same condition as bacterial overgrowth limited to the small bowel. Elevated methane production is particularly associated with constipation.²

This distinction can be useful when interpreting breath testing and deciding whether constipation should be assessed and treated as part of the overall digestive picture.

Our Approach to SIBO

At Tangible Health, we focus on determining whether SIBO is a plausible contributor to your symptoms and what factors may be increasing the likelihood of recurrence.

Your Digestive & Bowel Patterns
We review bloating, gas, abdominal discomfort, diarrhea or constipation, meal-related symptoms, nausea, previous diagnoses, and whether symptoms changed after previous antibiotic or dietary treatment.

Your SIBO Risk Factors
We look for factors that make SIBO more likely, such as previous gastrointestinal surgery, significant motility problems, medications that slow bowel movement, structural digestive conditions, or documented nutrient malabsorption. If the main symptoms are otherwise typical of IBS or functional bloating without clear SIBO risk factors, we avoid assuming bacterial overgrowth is necessarily the underlying explanation.³˒⁴

Your Goals
Your priorities may include reducing bloating or bowel symptoms, understanding a previous breath-test result, improving nutritional status, preventing unnecessary food restriction, addressing constipation or motility concerns, or reducing recurrence after previous SIBO treatment. Your care plan is developed around your symptom pattern, diagnosis, and goals.

Treatments That May Be Included

Treatment depends on whether SIBO has been appropriately diagnosed and whether an underlying condition is contributing. Your individualized care plan may include:

  • Clinical Nutrition to maintain adequate nutrition, identify foods that meaningfully worsen symptoms, and use temporary dietary modifications when appropriate

  • Lifestyle Medicine to support bowel regularity, movement, sleep, meal patterns, and other factors relevant to digestive function

  • Nutraceuticals & Supplements when there is a specific nutritional deficiency or other clinical indication

  • Botanical Medicine in selected situations, with careful consideration of the limited evidence for herbal antimicrobial protocols compared with established medical treatment

  • Naturopathic Counselling when stress or gut-brain interactions are contributing to symptom burden

  • Medication & Supplement Review to identify medications that may affect intestinal motility or digestive symptoms

  • Collaborative Care with a family doctor or gastroenterologist for diagnosis, antibiotic treatment, investigation of underlying conditions, or persistent symptoms

Antibiotics are the main established medical treatment used to reduce bacterial overgrowth, while correcting nutrient deficiencies and addressing an identifiable underlying cause are also important parts of management.¹˒⁵ Diet can help manage symptoms, but a restrictive diet by itself should not be described as “killing” or eradicating SIBO. Long-term unnecessary restriction can also make it harder to meet nutritional needs.

What to Expect

Initial Assessment
We begin with a detailed review of your bloating, gas, abdominal symptoms, bowel habits, diet, symptom timing, medications and supplements, previous gastrointestinal surgery or conditions, nutrient status, previous breath testing, and any previous SIBO treatments.

SIBO Risk & Diagnostic Review
We assess whether your history makes SIBO reasonably likely and review any previous testing in context. Glucose or lactulose hydrogen and methane breath tests are commonly used because they are non-invasive, but they have important limitations and can produce false-positive or false-negative results.²˒³˒⁴ This is particularly important when breath testing is used in people whose symptoms could otherwise be explained by IBS or another disorder of gut-brain interaction. A breath-test result should therefore be interpreted alongside symptoms and clinical risk factors rather than treated as a diagnosis in isolation.³˒⁴

Personalized Plan
Your care plan is developed around your symptoms, SIBO risk factors, test results when available, bowel pattern, nutritional needs, medical history, previous treatment response, and goals. When antibiotic therapy or further investigation is appropriate, this can be coordinated with your medical team.

Ongoing Support
SIBO can recur, particularly when the factor that predisposed someone to bacterial overgrowth remains present. Follow-up focuses on symptom response, nutritional status, bowel function, and whether recurrent symptoms genuinely suggest recurrent SIBO or require assessment for another condition.¹˒⁵

When to Seek Support for SIBO

Consider speaking with a healthcare provider if you experience:

  • Persistent or recurrent bloating and abdominal discomfort

  • Ongoing diarrhea or significant changes in bowel habits

  • Recurrent symptoms after previous SIBO treatment

  • A history of gastrointestinal surgery alongside new digestive symptoms

  • Symptoms of possible malabsorption

  • Known nutritional deficiencies without a clear explanation

  • Persistent digestive symptoms despite reasonable dietary or IBS-directed treatment

Seek prompt medical assessment if symptoms include:

  • Significant or unexplained weight loss

  • Persistent vomiting

  • Blood in the stool or black stools

  • Severe or progressively worsening abdominal pain

  • Fever with significant digestive symptoms

  • Significant dehydration

  • Signs of malnutrition

These symptoms should not automatically be attributed to SIBO, since other gastrointestinal conditions may require investigation.

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Frequently Asked Questions

  • SIBO often occurs when intestinal movement is slowed or when structural changes allow bacteria to accumulate in the small intestine. Gastrointestinal surgery, certain motility disorders, medications, and other medical conditions may increase risk.¹˒⁵

  • Glucose or lactulose hydrogen breath testing is commonly used because it is non-invasive. Diagnosis should also consider symptoms, risk factors, medical history, and other possible causes of digestive symptoms.²˒³

  • They are useful in selected clinical situations but are not perfect tests. Intestinal transit and other factors can affect results, and recent expert reviews have raised particular concerns about using breath tests routinely to diagnose SIBO in people with uncomplicated IBS-like symptoms.³˒⁴

  • No. IBS is a disorder of gut-brain interaction characterized by recurrent abdominal pain and changes in bowel habits. SIBO refers to excessive bacteria in the small intestine. They can have similar symptoms, and the extent to which SIBO explains symptoms in people with IBS remains controversial.³˒⁴

  • SIBO refers to bacterial overgrowth in the small intestine. IMO refers to excessive methane production by methanogens, which are not bacteria and may live in the small or large intestine. IMO is particularly associated with constipation.²

  • Yes. Recurrence can occur, especially when an underlying structural or motility problem remains. Recurrent symptoms should be reassessed rather than assuming that every episode automatically requires another course of treatment.¹˒⁵

  • Not necessarily. Reducing fermentable carbohydrates may help symptoms such as bloating for some people, particularly when IBS overlaps, but diet alone has not been established as a way to eradicate SIBO. Any restrictive diet should ideally be temporary and followed by food reintroduction when appropriate.

  • Probiotics are not a universal SIBO treatment, and evidence varies considerably depending on the product and clinical situation. They should not automatically be used simply because SIBO involves intestinal bacteria.

  • Naturopathic care can help evaluate dietary patterns, nutritional status, bowel function, medications, motility-related factors, previous testing, and symptom patterns. Care can also support nutrition and symptom management while coordinating appropriate medical testing or antibiotic treatment when needed.

 

Related Care

SIBO may overlap with several areas of health. You may also benefit from:

Jennifer Tang
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