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

    Factors that may increase your chance of SBBO include:

  • Crohn’s disease
  • Irritable bowel syndrome (IBS)
  • Short bowel syndrome
  • Diverticulitis
  • Intestinal stricture (narrowing in the small intestine)
  • Digestive disorders, such as celiac disease or lactose intolerance
  • Blind loop syndrome (when part of the intestine is bypassed)
  • Intestinal infections, such as food poisoning or traveler’s diarrhea
  • Cirrhosis
  • Diabetes
  • Chronic pancreatitis
  • End-stage kidney or liver disease
  • 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:

  • Abdominal pain
  • Bloating and gas
  • Feeling of fullness
  • Constipation or diarrhea
  • Nutritional deficiencies, such as vitamins B12 , A, D, E, iron, or thiamine
  • Weight loss
  • Diagnosis

    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
  • Treatment

    The goals are to:

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

    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.