Small Bowel Bacterial Overgrowth



SIBO is often caused by a problem with the small intestine. Problems with the intestine may slow the flow of food. The slowed food may lead to more bacteria growing. Intestine problems may be caused by:

  • Problems that were there from birth
  • Injury
  • Surgery
  • Digestive disorders

Risk Factors

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

  • Crohn 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
  • A pancreas that is not making enough of the enzymes to break down food
  • Blind loop syndrome—part of the intestine is bypassed
  • Infections, such as food poisoning or traveler’s diarrhea
  • Cirrhosis
  • Diabetes
  • Chronic pancreatitis
  • End-stage kidney or liver disease

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

  • Past intestinal surgery
  • An blockage in the small intestine
  • Having a weakened immune system



A person with SIBO may have:

  • Belly pain
  • Bloating and gas
  • A feeling of fullness
  • Constipation or diarrhea
  • Weight loss


The doctor will ask about 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 certain sugars
  • Culture of intestinal fluid—a sample of fluid from the small bowel will be taken to see what bacteria is there



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


Antibiotics are often used to treat SIBO. Some may need to take antibiotics for a long 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 one that limits carbohydrates
  • Taking vitamins 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 fix a problem in the small bowel.


SIBO cannot be prevented.

This content is reviewed regularly and is updated when new and relevant evidence is made available. This information is neither intended nor implied to be a substitute for professional medical advice. Always seek the advice of your physician or other qualified health provider prior to starting any new treatment or with questions regarding a medical condition.

Edits to original content made by Denver Health.