Key Points about Small Intestinal Bacterial Overgrowth (SIBO)

  • SIBO occurs when there are extra or unusual bacteria present in the small intestine.
  • SIBO is also known as blind loop syndrome.
  • A breath test or small intestine aspirate and fluid culture can diagnose SIBO.  Blood, stool and imaging tests may also be used.
  • Treatment for SIBO usually includes antibiotic medications and nutritional therapy.


Small intestinal bacterial overgrowth – or SIBO – is a condition in which there are excessive amounts of bacteria present in the small intestine. Typically, these bacteria are not present in that area of the digestive tract. Another name for SIBO is blind loop syndrome. If not properly treated and managed, SIBO can lead to malnutrition, vitamin deficiency, osteoporosis (weak bones) or kidney stones.

Small Intestinal Bacterial Overgrowth causes 

There are a variety of potential causes of SIBO, which include:

  • Celiac disease
  • Complication of abdominal surgery, such as gastric bypass or gastrectomy (procedure that treats peptic ulcers and stomach cancer)
  • Crohn’s disease
  • Diabetes
  • Other conditions that slow the digestive process
  • Scleroderma
  • Structural problem of the small intestine, including scar tissue

Small Intestinal Bacterial Overgrowth risk factors

Factors that may increase your risk for developing SIBO are having:

  • A fistula (abnormal connection) between two segments of your bowel
  • An injury to your small intestine
  • Adhesions or scar tissue from prior abdominal surgery
  • Crohn’s disease
  • Diabetes
  • Diverticulosis of the small intestine
  • Intestinal lymphoma
  • Received radiation therapy to your abdomen
  • Scleroderma
  • Undergone gastrectomy
  • Undergone gastric bypass surgery

Small Intestinal Bacterial Overgrowth symptoms

The signs and symptoms of acute SIBO can include:

  • Abdominal pain
  • Bloating
  • Decreased appetite
  • Diarrhea
  • Feeling of uncomfortable fullness after eating
  • Malnutrition
  • Nausea
  • Unintended weight loss

Small Intestinal Bacterial Overgrowth diagnosis

Your gastroenterologist may use one or more of the following diagnostic tools to diagnose your SIBO:

Breath testing. In this test, you’ll drink a mixture of glucose (sugar) and water. Then, the technician will measure the level of hydrogen or methane in your breath. This will help determine the levels of bacterial overgrowth in your small intestine.

Small intestine aspirate and fluid culture. In this test, your specialist threads a long, flexible tube (endoscopy) through your mouth, down your throat and into your upper digestive tract to your small intestine. Once there, your specialist withdraws a small sample of intestinal fluid. Technicians test this sample in the laboratory for the overgrowth of bacteria. 

Blood test. This test can check for vitamin deficiency.

Stool test. This test can check how your body is absorbing fat.

Imaging tests. Your specialist may order an imaging test – such as an X-ray, computerized tomography (CT) scan or magnetic resonance imaging (MRI) scan – to check for structural abnormalities of your intestine.

Small Intestinal Bacterial Overgrowth treatment

Treatment for SIBO focuses on correcting the underlying problem, when possible. Treatment may include:

Antibiotic medication. Your specialist may prescribe antibiotic medication to help reduce the overgrowth of bacteria that has caused SIBO.

Nutritional therapy. Long-term management and prevention of the reoccurrence of SIBO almost always involve nutritional therapy. Nutritional supplements, such as vitamin B-12 injections or calcium and iron supplements, may help. You may also need to follow a lactose-free diet.

When should I seek care?

If you experience any of these symptoms, start by voicing your concerns and symptoms to your primary care provider. From there, your doctor may suggest seeing a gastroenterologist for more specialized treatment.

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