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Small Intestinal Bacterial Overgrowth: Part 1

The connections between gut function, health, and disease are complex.  When the normal function and health of a person’s GI tract are compromised, any organ system of the body can be adversely affected.  In a healthy person, there is typically a normal amount and type of bacteria in the gut. Some of these bacteria reside in the small intestine, while a much larger number reside in the large intestine. Small intestinal bacterial overgrowth (SIBO) is characterized by a higher than normal amount of bacteria in the small intestine1 and has been shown to play a role in irritable bowel syndrome (IBS).2  An imbalance in gut microbes, including SIBO, can cause symptoms of IBS including abdominal pain and/or discomfort, bloating, and irregular stool form and passage.2

Testing for SIBO

Small bowel culture1,3

The gold standard for SIBO diagnosis is a culture of the upper gut aspirate. A small tube is inserted through the mouth, down through the stomach, and into the first part of the intestine. It suctions out a small amount of fluid from the small intestine, which is then incubated for 5 days to see how many bacteria grow. A result equal to or greater than 103 cfu/mL indicates a positive SIBO test. Limitations of this test are that it’s invasive, expensive, and there’s a potential for sample contamination.

Breath test2,3

Breath tests have become common due to the fact that they are noninvasive and patient-friendly. They can be done at a medical facility or at home with an at-home test kit. A patient ingests a carbohydrate substrate (glucose or lactulose) which is broken down in the stomach, leading to the production of hydrogen and methane. The bloodstream absorbs some of the gas which is then exhaled in breath. Breath samples are collected at baseline and every 15 minutes for a specified amount of time. Patients who produce hydrogen alone are more likely to have diarrhea, whereas patients who have elevated methane are more likely to have constipation.

Stool testing

Comprehensive stool testing is an option for a more extensive look at the microbiome, inflammation, digestive markers, and potential pathogens. Stool testing generally gives us a picture of what is in the large intestine/colon, so it tell us about SIBO but can be helpful in guiding treatment and overall gut restoration. 

Stay tuned for Part 2 of the SIBO blog post coming next week in which we’ll discuss treatment options for SIBO.

Gut health is something we are passionate about at PharmToTable. If you are experiencing gas, bloating, abdominal pain, heartburn, or other GI symptoms. Please reach out. Healing the gut is the first step on the journey back to wellness and thriving. You can learn more about the functional medicine approach by joining our next discovery class or book an appointment to work with our team!

Written by Kristina Burban, PharmD during her internship with our team.


  1. Drake LE, Guilliams TG. Small intestinal bacterial overgrowth (SIBO): diagnostic challenges and functional solutions. Point Institute. 2018;14(2)1-15.
  2. Ghoshal UC, Shukla R, Ghoshal U. Small Intestinal Bacterial Overgrowth and Irritable Bowel Syndrome: A Bridge between Functional Organic Dichotomy. Gut Liver. 2017;11(2):196–208. doi:10.5009/gnl16126
  3. Rao SSC, Bhagatwala J. Small Intestinal Bacterial Overgrowth: Clinical Features and Therapeutic Management. Clin Transl Gastroenterol. 2019;10(10):e00078.
  4. Dukowicz AC, Lacy BE, Levine GM. Small intestinal bacterial overgrowth: a comprehensive review. Gastroenterol Hepatol (N Y). 2007;3(2):112-122.

1 thought on “Small Intestinal Bacterial Overgrowth: Part 1

  1. […] part one of our small intestinal bacterial overgrowth (SIBO) blog post, we defined SIBO and discussed risk […]

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