In order to diagnose small intestinal bacterial overgrowth (SIBO), you may have tests to check for bacterial overgrowth in your small intestine, poor fat absorption, or other problems that may be causing or contributing to your symptoms. Common tests include:

  • Breath testing. This type of noninvasive test measures the amount of hydrogen or methane that you breathe out after drinking a mixture of glucose and water. A rapid rise in exhaled hydrogen or methane may indicate bacterial overgrowth in your small intestine. Although widely available, breath testing is less specific than other types of tests for diagnosing bacterial overgrowth.
  • Small intestine aspirate and fluid culture. This is currently the gold standard test for bacterial overgrowth. To obtain the fluid sample, doctors pass a long, flexible tube (endoscope) down your throat and through your upper digestive tract to your small intestine. A sample of intestinal fluid is withdrawn and then tested in a laboratory for the growth of bacteria.

In addition to these tests, your doctor may recommend blood testing to look for vitamin deficiency or a stool evaluation to test for fat malabsorption. In some cases, your doctor may recommend imaging tests, such as X-rays, computerized tomography (CT) scanning or magnetic resonance imaging (MRI) to look for structural abnormalities of the intestine.


Whenever possible, doctors treat small intestinal bacterial overgrowth (SIBO) by dealing with the underlying problem — for example, by surgically repairing a postoperative loop, stricture or fistula. But a loop can't always be reversed. In that case, treatment focuses on correcting nutritional deficiencies and eliminating bacterial overgrowth.

Antibiotic therapy

For most people, the initial way to treat bacterial overgrowth is with antibiotics. Doctors may start this treatment if your symptoms and medical history strongly suggest this is the cause, even when test results are inconclusive or without any testing at all. Testing may be performed if antibiotic treatment is not effective.

A short course of antibiotics often significantly reduces the number of abnormal bacteria. But bacteria can return when the antibiotic is discontinued, so treatment may need to be long term. Some people with a loop in their small intestine may go for long periods without needing antibiotics, while others may need them regularly.

Doctors may also switch among different antibiotics to help prevent bacterial resistance. Antibiotics wipe out most intestinal bacteria, both normal and abnormal. As a result, antibiotics can cause some of the very problems they're trying to cure, including diarrhea. Switching among different drugs can help avoid this problem.

Nutritional support

Correcting nutritional deficiencies is a crucial part of treating SIBO, particularly in people with severe weight loss. Malnutrition can be treated, but the damage it causes can't always be reversed.

These treatments may improve vitamin deficiencies, reduce intestinal distress and help with weight gain:

  • Nutritional supplements. People with SIBO may need intramuscular injections of vitamin B-12, as well as oral vitamins, calcium and iron supplements.
  • Lactose-free diet. Damage to the small intestine may cause you to lose the ability to digest milk sugar (lactose). In that case, it's important to avoid most lactose-containing products, or use lactase preparations that help digest milk sugar.

    Some affected people may tolerate yogurt because the bacteria used in the culturing process naturally break down lactose.

Preparing for your appointment

If you have signs and symptoms that are common to small intestinal bacterial overgrowth (SIBO), make an appointment with your doctor. After an initial evaluation, you may be referred to a doctor who specializes in treatment of digestive disorders (gastroenterologist).

Here's some information to help you get ready for your appointment, and what to expect from your doctor.

  • Write down your symptoms, including when they started and how they may have changed or worsened over time.
  • Bring your medical records, especially if you have had surgery on your stomach or intestines, have any known bowel condition, or have received radiation to the abdomen or pelvis.
  • Make a list of all your medications, vitamins and supplements.
  • Write down your key medical information, including other conditions with which you've been diagnosed. Be sure to let your doctor know about any abdominal surgery you've had.
  • Write down key personal information, including any recent changes or stressors in your life. These factors can be connected to digestive signs and symptoms.
  • Take a family member or friend along, if possible. It can be difficult to remember all the information provided during an appointment. Someone who accompanies you may remember something that you missed or forgot.
  • Write down questions to ask your doctor. Creating your list of questions in advance can help you make the most of your time with your doctor.

Don't hesitate to ask questions. Some basic questions to ask your doctor include:

  • What is the most likely cause of my condition?
  • What treatment approach do you recommend?
  • Are there any side effects associated with the medications you're prescribing?
  • I have other conditions. How can I treat them?
  • Will I need to stay on medications long term?
  • How often will you see me to monitor my progress?
  • Should I take any nutritional supplements?
  • Do I have any vitamin deficiencies?
  • Are there any lifestyle or dietary changes I can make to help reduce or manage my symptoms?

What to expect from your doctor

Your doctor is likely to ask you a number of questions. Being ready to answer them may reserve time to go over points you want to spend more time on. You may be asked:

  • Have you ever had abdominal surgery?
  • What are your symptoms?
  • When did you first notice these symptoms?
  • Do your symptoms come and go or stay about the same?
  • Is your pain cramp-like?
  • Does your pain radiate to other parts of your abdomen or to your back?
  • Have you lost weight without trying?
  • Have you noticed a change in your stools?
  • Have your signs and symptoms included vomiting?
  • Have your signs and symptoms included a fever?
  • Has anyone close to you had similar signs or symptoms recently?
  • What is your typical daily diet?
  • Have you ever been diagnosed with a food allergy or with lactose intolerance?
  • Have you been diagnosed with any other medical conditions?
  • What medications are you taking, including prescription and over-the-counter medications, vitamins, herbs, and supplements?
  • Do you have any family history of bowel disorders or colon cancer?
  • Have you ever had radiation therapy to your abdomen or pelvis?
  • Have you ever had kidney stones?
  • Have you ever had problems with your pancreas?
  • Do you have Crohn's disease?

Jan 06, 2022

  1. Ramirez PT, et al., eds. Management of bowel surgery complications. In: Principles of Gynecologic Oncology Surgery. Elsevier; 2019. https://www.clinicalkey.com. Accessed Jan. 17, 2020.
  2. Adike A, et al. Small intestinal bacterial overgrowth: Nutritional implications, diagnosis, and management. Gastroenterological Clinics of North America. 2018; doi:10.1016/j.gtc.2017.09.008.
  3. Rodriguez DA, et al. Small intestinal bacterial overgrowth in children: A state-of-the-art review. Frontiers in Pediatrics. 2019; doi:10.3389/fped.2019.00363.
  4. Ferri FF. Small bowel bacterial overgrowth (SIBO). In: Ferri's Clinical Advisor 2020. Elsevier; 2020. https://www.clinicalkey.com. Accessed Jan. 17, 2020.
  5. Cameron AM, et al. Management of motility disorders of the stomach and small bowel. In: Current Surgical Therapy. 13th ed. Elsevier; 2020. https://www.clinicalkey.com. Accessed Jan. 17, 2020.
  6. Rao SS, et al. Small intestinal bacterial overgrowth: Clinical features and therapeutic management. Clinical and Translational Gastroenterology. 2019; doi:10.14309/ctg.0000000000000078.
  7. Kashyap PC (expert opinion). Mayo Clinic. Jan. 24, 2020.


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