What Causes SIBO?
The small intestine normally contains relatively few bacteria, unlike the large intestine. Bacteria levels in the small intestine are maintained by peristalsis, gastric acid, and bile. However, certain factors can interfere with these mechanisms, resulting in migration and subsequent proliferation of bacteria in the small intestine. Factors that contribute to SIBO include anatomic anomalies, surgical sequelae, systemic disease, and certain medications.
Anatomic anomalies
Anatomic anomalies, such as small intestine diverticula or obstructions, can increase the risk for developing SIBO. The diverticula provide pockets in the lining of the small intestine where bacteria can flourish, while obstructions, such as tumors, hinder gut motility. Patients with hypochlorhydria or achlorhydria may also develop SIBO, as they lack sufficient gastric acid and bile to mitigate bacterial overgrowth.
Surgical sequelae
Examples of surgical sequelae that could lead to SIBO include abdominal surgery in which bacteria migrate into the small intestine, strictures or scar tissue from abdominal surgeries that prevent satisfactory peristalsis, and peristalsis after abdominal procedures.
Systemic conditions
Systemic diseases that can contribute to the development of SIBO include:
- Acquired immunodeficiency syndrome (AIDS)
- Celiac disease
- Cirrhosis
- Colon cancer
- Crohns disease
- Diabetes
- Human immunodeficiency virus (HIV)
- Inflammatory bowel disease
- Irritable bowel syndrome (IBS)
- Lupus
- Pancreatitis
- Renal failure
SIBO and GLP-1s
Recent studies suggest that patients taking glucagon-like peptide-1 (GLP-1) medications have a slightly increased short-term risk of developing SIBO. Glucagon-like peptide-1 receptor agonists (GLP-1 RAs) have become widely used in the U.S. to help patients with type 2 diabetes mellitus maintain glycemic control. The medications have also been used to promote weight loss, lower blood pressure, and improve renal function.
GLP-1 RAs and their brand names that have been approved by the Food and Drug Administration (FDA) include:
- Dulaglutide (Trulicity)
- Exenatide (Byetta, Bydureon, Bydureon BCise)
- Liraglutide (Victoza, Saxenda)
- Lixisenatide (Adlyxin)
- Semaglutide (Ozempic, Rybelsus, Wegovy)
Tirzepatide (brand names Mounjaro, Zepbound), a dual glucose-dependent insulinotropic peptide and GLP-1 RA, is also prescribed for weight loss.
While delayed gastric emptying has not been linked to an increased risk of developing SIBO, delayed orocecal and small intestinal transitwhich are known symptoms of GLP-1 medications can predispose patients to developing SIBO. Symptom-driven SIBO breath-test evaluation may be warranted in patients initiating these agents, a 2025 study advises.
Patients taking broad-spectrum antibiotics should also be wary of developing SIBO. Broad-spectrum antibiotics kill both harmful and beneficial bacteria, allowing harmful bacteria to overgrow unchecked.
What are the Symptoms of SIBO?
SIBO is associated with many symptoms. Patients with SIBO can present with any number of the following symptoms:
- Abdominal bloating
- Abdominal pain or discomfort
- Constipation
- Diarrhea
- Indigestion
- Nausea
- Weight loss
- Flatulence
- Steatorrhea
Prolonged or severe SIBO can also lead to poor micronutrient absorption, causing serious conditions such as malnutrition, anemia, vitamin deficiencies, unintentional weight loss, osteoporosis, kidney stones, nerve damage, and mental confusion.
How is SIBO Diagnosed?
The most common testing methods that healthcare providers use for SIBO are breath tests or bowel aspiration. The criteria to diagnose SIBO are:
- Positive hydrogen lactulose or glucose breath test
OR
- Presence of ≥103 to 105 colony-forming units per milliliter of jejunal aspirate
Breath tests involve a patient consuming a substrate and exhaling into a receptacle at multiple time intervals after ingestion. Microbial metabolism produces hydrogen, hydrogen sulfide, and methane, which are expelled through exhalation. Therefore, elevated levels of hydrogen or methane in the exhaled sample indicate an overpopulation of microbes in the small intestine. The type or types of SIBO can be determined based on gas concentrations in patients samples.
Intestinal methanogen overgrowth (IMO) is often grouped with SIBO, as it was previously known as methane-dominant SIBO, although further research has determined that methanogens, rather than bacteria, produce methane.
How is SIBO Treated?
SIBO is commonly treated with the administration of antibiotics, such as rifaximin or metronidazole, to reduce bacterial overgrowth. Administer rifaximin 1650 mg/day for two weeks for patients with hydrogen-predominant bacterial overgrowth, and combine neomycin 1000 mg/day and rifaximin 1650 mg/day for two weeks for patients with methane-predominant bacterial overgrowth,StatPearls from the National Library of Medicine recommends. Additionally, nutritional deficiencies should be addressed if needed.
About 45% of patients experience SIBO recurrence within nine months after antibiotic therapy. In such cases, specialists recommend administering an alternate antibiotic.
Patients may find symptom relief by consuming foods rich in probiotics and abiding by a diet containing limited fermentable oligosaccharides, disaccharides, monosaccharides, and polyols (FODMAP), although expert opinion of the diets efficacy remains mixed. The low-FODMAP diet aims to decrease the opportunity for bacteria to flourish in the gut by limiting the patients intake of carbohydrates.
Nurses and other healthcare providers should educate patients on the types of food that contribute to SIBO symptoms. Its also important to assess the patients food literacy and provide them with appropriate resources to ensure consistent, comprehensive care and adherence to the plan of treatment. Collaboration with dieticians or nutritionists can be invaluable in this process.
Conclusion
Small intestinal bacterial overgrowth (SIBO) is a gastrointestinal condition in which bacteria overpopulate the small intestine. The condition can be caused by mechanical, systemic, or environmental means. Nurses should conduct thorough histories, with emphasis on gastrointestinal issues, dietary habits, and gastrointestinal surgeries. The condition is treated with antibiotics, and symptoms may be managed with diet.
About the Author
Savannah Schmidt is a medical content writer and editor with five years of professional experience. She has a BA in English Literature and has had a hand in creating, editing, and publishing over 500 pieces of content for CEUs for healthcare and medical coding professionals.
Savannah is an independent contributor to CEUfast's Nursing Blog Program. Please note that the views, thoughts, and opinions expressed in this blog post are solely those of the independent contributor and do not necessarily represent those of CEUfast. This blog post is not medical advice. Always consult with your personal healthcare provider for any health-related questions or concerns.
If you want to learn more about CEUfast's Nursing Blog Program or would like to submit a blog post for consideration, please visit https://ceufast.com/blog/submissions.
References
Calderon, G., Siwiec, R., Bohm, M., et al. (2021). Delayed Gastric Emptying Is Not Associated with a Microbiological Diagnosis of Small Intestinal Bacterial Overgrowth. Digestive Diseases and Sciences, 66, 160166. https://doi.org/10.1007/s10620-020-06153-1
Cutler, R., Sridharan, M., Sullivan, M., Doran, A., Frye, J. (2024). Weighting on Methane: Weight Loss Medications Associated With Increased Incidence of SIBO. The American Journal of Gastroenterology 119(10S), S546-S547. https://doi.org/10.14309/01.ajg.0001032536.53564.9a
Feingold, K. (updated 2024). Oral and Injectable (Non-Insulin) Pharmacological Agents for the Treatment of Type 2 Diabetes. Endotext. https://www.ncbi.nlm.nih.gov/books/NBK279141/
Gandhi, A., Shah, A., Jones, M., Koloski, N., Talley, N., Morrison, M., & Holtmann, G. (2021). Methane positive small intestinal bacterial overgrowth in inflammatory bowel disease and irritable bowel syndrome: A systematic review and meta-analysis. Gut microbes, 13(1), 1933313. https://doi.org/10.1080/19490976.2021.1933313
SIBO Awareness. (n.d.). Root causes of SIBO. SIBO Awareness. https://siboawareness.org/root-causes-sibo
Silva, P., Araújo, R., Lopes, F., Ray, S. (2023). Nutrition and Food Literacy: Framing the Challenges to Health Communication. Nutrients, 15(22), 4708. https://doi.org/10.3390/nu15224708
Skrzydo-Radomaska, B., & Cukrowska, B. (2022). How to Recognize and Treat Small Intestinal Bacterial Overgrowth?. Journal of Clinical Medicine, 11(20), 6017. https://doi.org/10.3390/jcm11206017
Sorathia, S., Chippa V., Rivas J. (2023). Small Intestinal Bacterial Overgrowth. StatPearls Publishing. https://www.ncbi.nlm.nih.gov/books/NBK546634/
Sun, Y., Veccia, D., Liu, B. D. X., Tse, W., Fass, R., & Song, G. (2025). Diagnostic Evaluation of an Increased Risk of Developing Small Intestinal Bacterial Overgrowth Associated with Glucagon-like Peptide-1 (GLP-1) Receptor Agonists and Dual GLP-1/GIP Receptor Agonists: A Global Retrospective Multicenter Cohort Analysis. Diagnostics, 15(17), 2264. https://doi.org/10.3390/diagnostics15172264
About the Author
Savannah Schmidt is a medical content writer and editor with five years of professional experience. She has a BA in English Literature and has had a hand in creating, editing, and publishing over 500 pieces of content for CEUs for healthcare and medical coding professionals.
<Savannah is an independent contributor to CEUfast's Nursing Blog Program. Please note that the views, thoughts, and opinions expressed in this blog post are solely those of the independent contributor and do not necessarily represent those of CEUfast. This blog post is not medical advice. Always consult with your personal healthcare provider for any health-related questions or concerns.
If you want to learn more about CEUfast's Nursing Blog Program or would like to submit a blog post for consideration, please visit https://ceufast.com/blog/submissions.
