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Small Intestinal Bacterial Overgrowth (SIBO)


What is Small Intestinal Bacterial Overgrowth?

Small intestinal bacterial overgrowth, referred to as SIBO, is a serious condition that occurs when bacteria that normally live in other parts of the gut begin to grow abnormally in the small intestine. The presence of certain bacteria in the small intestine leads to various uncomfortable symptoms.

What causes SIBO?

Flexible sigmoidoscopy may be recommended if your doctor suspects one of the following digestive conditions:

SIBO may occur when there are anatomic abnormalities in the small bowel. Additional factors that may contribute to this condition include:

  • The immune system is compromised.
  • The pH of the small bowel changes.
  • There is a malfunction in the muscular activity of the small intestine, leaving food and bacteria in the area.


Risk factors for the development of SIBO include:

  • Previous long-term or recurrent use of antibiotics
  • Chron’s disease
  • Previous bowel surgery
  • Low stomach acid
  • Longstanding celiac disease
  • Irritable bowel syndrome
  • Type I and II diabetes mellitus


 What are some SIBO symptoms?

  • Bloating
  • Gas and belching
  • Abdominal cramps
  • Diarrhea or constipation
  • Heartburn
  • Food sensitivities
  • Nausea
  • Fatigue
  • Joint pain
  • Headaches
  • Eczema
  • Skin rashes
  • Vitamin B12 deficiency
  • Mood symptoms such as depression


How is SIBO diagnosed?

SIBO can be a challenging diagnosis that may not be made until a person sees a specialist. In our gastroenterology office, patients undergo a thorough consultation, medical history, and review of symptoms. A physical examination is also performed. This includes gently palpating the abdomen and ordering or performing various tests.

The Lactulose Breath Test is a common method of screening for SIBO in patients who present with characteristic symptoms. This test takes an hours-long observation of the activity of bacteria in the intestines. Bacteria that live in the intestinal system digest foods that pass through. This results in the production of gasses that permeate the intestinal walls to enter the bloodstream. Gasses in the bloodstream travel to the lungs and are expired in exhalation breaths. Lactulose breath testing delivers “food” to bacteria and then measures the levels of hydrogen and methane gasses in the breath. Which type of gas and the level of the gas inform the doctor about the location of bacterial fermentation in the intestine.

What is the Lactulose Breath Test for SIBO?

In this test, lactulose, which is a non-absorbable sugar solution, is swallowed and hydrogen and methane gases are measured in the patient’s breath at regular intervals.  Gas levels rise as the sugar solution passes through the intestine resulting from fermentation of the sugar by bacteria. If the gas levels rise quickly and to an abnormal level, a diagnosis of small intestinal bacterial overgrowth can be made

How accurate are the Lactulose Breath Test results?

Breath testing is a noninvasive method of diagnosing various conditions. This method has been widely used for many years at institutions including Johns Hopkins Hospital and Health System. The premise of breath testing is to measure the levels of certain gases to expedite accurate diagnoses. We use proven testing protocols and carefully follow manufacturer guidelines to secure definitive results for our patients.

How to prepare for the SIBO breath test:

For accurate test results, certain foods, drinks, supplements, and medicine must be avoided before the test:

  • Wait at least 4 weeks from colonoscopy or barium enema before beginning the test.
  • If you are using antibiotics, antifungals or Pepto-Bismol, wait at least 2 weeks from your last dose before beginning the test
  • 1 week before the test: Avoid the use of laxatives, stool softeners and/or stool bulking agents (Ex-Lax, Colace, Metamucil, Fibercon) as well as the use of antacids containing aluminum or magnesium hydroxide (i.e. Maalox liquid, Equate, Milk of Magnesia, Rolaids, Mylanta)
  • 2 days before the test: Stop eating high fiber and lactose-containing foods for a full 36 hours before specimen collection. This usually means starting with the dinner meal two nights before doing the test. Please click on the link below for a list of allowed/non-allowed foods and a sample diet.
  • Foods you CAN eat before you start your 12-hour fast: baked or broiled chicken, white bread only, plain steamed white rice, eggs, clear chicken or beef broth with no vegetable pieces
  • Stop eating and drinking anything other than water at least 12 hours prior to specimen collection
  • The day of the test: Do not drink anything for the first hour of collection. After the first hour, you may drink water only. Continue fasting until you complete the entire test. Do not chew gum or tobacco, smoke, eat breath mints or candy, use toothpaste, nap or exercise vigorously for at least 30 minutes before or at any time during the test.


What are the SIBO treatment options?

The treatment protocol for SIBO is dependent upon the type of gas that is found in the breath. When there is more hydrogen in the breath, the patient is said to be hydrogen-dominant. The alternative is that the patient is methane-dominant. Which type of gas is produced relates to the type of bacteria present in the small intestine. In either case, the standard approach to treating SIBO is a course of antibiotics.

Hydrogen-Predominant SIBO

This may be treated with rifaximin. Patients may supplement their treatment protocol with dietary changes that include the consumption of cinnamon, oregano, and herbs like neem.

Methane-Predominant SIBO

This is commonly treated with a combination of antibiotics, such as rifaximin and neomycin. Herbs such as oregano and cinnamon may increase the efficacy of treatment.

Recurrent SIBO

Many people experience recurrent bouts of SIBO symptoms. This is not because the condition is not treatable, curable even, but because every person is unique. Not every person responds to every antibiotic. Seeing that antibiotics are the primary treatment regimen for SIBO, we must understand that it may be necessary to try a different antibiotic medication if improvement is not achieved right away.

Another reason why SIBO may recur is that the initial round of antibiotics simply did not fully eradicate the overgrowth that has occurred, so the bacteria that are triggering symptoms persist. Finally, it is necessary to identify the underlying risk factor that is contributing to SIBO and addressing that. SIBO is not a simple matter of an imbalance between “good and bad” gut bacteria. Patients experiencing the symptoms of this condition should not rely on probiotics alone to reduce symptoms. If symptoms of SIBO persist or recur, talk to your doctor to develop a treatment protocol customized to your needs.

What are SIBO risk factors if left untreated?

SIBO is an underdiagnosed condition that could lead to dehydration and malnutrition if not adequately treated. If you suspect you may have this condition, talk to your primary care physician or contact our office to schedule your SIBO breath test.

Procedure Instructions

Lactose Intolerance Breath Test Instructions

Patient Escort Policy

Patient Education Videos

In the following educational videos about upper endoscopy and colonoscopy, ASGE doctors walk viewers through both procedures featuring real patients – from preparation instructions to what happens during the procedures and what to expect after the exams. Click on the links below to watch videos.


Upper Endoscopy