Small Bowel Bacterial Overgrowth



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:

  • 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 needed to break down food
  • 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

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:

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


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.

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.