by EBSCO Medical Review Board
(SIBO; Small Bowel Bacterial Overgrowth; SBBO)


Bacteria normally exists in the intestines. It plays a role in digestion and overall health. Small intestine bacterial overgrowth (SIBO) is when there is too much bacteria in the small intestine.

The Small Intestines
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SIBO is often caused by a problem with the small intestine. Damage or defects to the intestine may slow the flow of food. The slowed food may encourage the increased growth of bacteria. Problems of the intestine may be caused by:

  • Birth defect
  • Injury
  • Surgery
  • Digestive disorders

Risk Factors

Any condition that affects how food moves through the intestines may increase the risk of SIBO. Some problems are:

This problem is also more common in older adults. Other risk factors are:

  • Prior intestinal surgery
  • An obstruction in the small intestine
  • Having a weakened immune system


Problems may be:


The doctor will ask about your symptoms and health history. A physical exam will be done.

Tests may include:

  • Blood tests
  • Breath tests—to look for certain gases after fasting and eating specific sugars
  • Culture of intestinal fluid—a sample of fluid from the small bowel will be taken to see what bacteria is present


Any underlying health problems will need to be treated. The goal of treatment is to lower the levels of harmful bacteria.


Antibiotics are often used to treat SIBO. Usually treatment is temporary. Some may need to take antibiotics for a longer period.

Nutritional Support

Proper nutrients can help bring back the balance of bacteria. Steps that may help are:

  • Working with a dietitian
  • Following a special diet, such as a carbohydrate-restricted diet
  • Taking vitamins and/or supplements
  • Taking probiotics

Some people may need tube feeding with a special formula.


Surgery may be needed for severe SIBO. It may be done to correct a problem in the small bowel.


There are no known guidelines to prevent this health problem.


American Gastroenterological Association 

National Institute of Diabetes and Digestive and Kidney Diseases 


Canadian Association of Gastroenterology 

Canadian Digestive Health Foundation 


Hydrogen breath test for lactose intolerance. Cleveland Clinic website. Available at: Accessed August 20, 2021.

Short bowel syndrome. EBSCO DynaMed website. Available at: Accessed August 20, 2021.

Small intestinal bacterial overgrowth (SIBO). Merck Manual Professional Version website. Available at: Accessed August 20, 2021.

Revision Information

  • Reviewer: EBSCO Medical Review Board James Cornell, MD
  • Review Date: 07/2021
  • Update Date: 08/20/2021