Small Bowel Bacterial Overgrowth

(SBBO; Bacterial Overgrowth, Small Bowel; Small Intestine Bacterial Overgrowth; SIBO; Bacterial Overgrowth, Small Intestine)



Small bowel bacterial overgrowth (SBBO) occurs when there is a build-up of too much bacteria in the small bowel.

The Small Intestines

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SBBO is often caused by an abnormality in the small bowel. Food is not able to flow properly though the intestines. Conditions that may cause this include:

  • Birth defect
  • Injury
  • Surgery
  • Digestive disorders

Risk Factors

Risk Factors

Factors that may increase your chance of SBBO include:

Other risk factors include:

  • Intestinal surgery
  • An obstruction in the small intestine
  • Weakened immune system
  • Older age

Any condition that affects how food moves through the small bowel may increase the risk of SBBO.



SBBO may cause:



Your doctor will ask about your symptoms and medical history. A physical exam will be done.

Tests may include

  • Blood tests
  • Breath tests—to analyze certain gases that may be present after fasting and eating specific sugars
  • Culture of intestinal fluid (aspirate)—a catheter is used to get a sample of fluid from the small bowel



The goals are to:

  • Reduce the levels of harmful bacteria in the small bowel
  • Treat the underlying condition


Antibiotics are often prescribed to treat SBBO. Usually treatment is temporary, but in some cases you may need to take antibiotics for a longer period.

Nutritional Support

To make sure that you get the proper nutrients, you may need to:

  • Work with a dietitian
  • Follow a special diet, such as a carbohydrate-restricted diet
  • Take vitamins and/or supplements
  • Take probiotics

In some cases, tube feeding is needed with a special formula.


For severe cases, surgery may be needed. This is done to correct an abnormality in the small bowel.



If you have any of the conditions that are linked to SBBO, get proper treatment. This may reduce your chance of having a build-up of bacteria in the small bowel.


Gastro—American Gastroenterological Association

National Digestive Diseases Information Clearinghouse


Canadian Association of Gastroenterology

Canadian Digestive Health Foundation


Bacterial overgrowth syndrome. The Merck Manual Professional Edition website. Available at:
Updated May 2014. Accessed September 29, 2014.

Bures J, Cyrany J, Kohoutova D, et al. Small intestinal bacterial overgrowth syndrome. World J Gastroenterol. 2010;16(24):2978–2990.

Lactose and glucose hydrogen breath test. Cleveland Clinic website. Available at:
Accessed September 29, 2014.

Lin H. Small intestinal bacterial overgrowth. JAMA. 2004;292(7):852-858.

Parrish C. Nutritional consequences of small intestinal bacterial overgrowth. University of Virginia, School of Medicine website. Available at:
Published December 2008. Accessed September 29, 2014.

Short bowel syndrome. EBSCO DynaMed website. Available at:
Updated May 6, 2014. Accessed September 29, 2014.

Vanderhoof J, Young R. Bacterial overgrowth. The Oley Foundation website. Available at:
Accessed September 29, 2014.

Vanderhoof J, Young R, Murray N, Kaufman SS. Treatment strategies for small bowel bacterial overgrowth in short bowel syndrome. J Pediatr Gastroenterol Nutr. 1998;27(2):155-160.

Last reviewed August 2014 by Daus Mahnke, MD
Last Updated: 9/30/2013

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