Small Intestinal Bacterial Overgrowth (SIBO)

Medically Reviewed by Minesh Khatri, MD on September 02, 2022

Small intestinal bacterial overgrowth (SIBO) is when you have too much bacteria in your small intestine.

Everyone has bacteria in their gut; they play a key part in digestion. But if things get out of balance, problems can happen.

SIBO can be treated, and lifestyle changes may be all it takes.

SIBO may cause:

SIBO usually starts when your small intestine doesn’t move food along the way it should. Bacteria grow and stick around too long. If the “good” bacteria that help you digest food can’t keep up with the harmful bacteria, the “bad” germs can multiply too fast, leading to an imbalance.

Things that can cause SIBO or make it more likely include:

Age. Older adults are at higher risk because they may make less of the gastric acid that breaks down food. They’re also more likely to have diverticulosis.

Anatomy. You may have a small intestine with an unusual shape. Physical differences in your gut can make food move more slowly than it should and allow bacteria to grow. These may happen because of:

  • Diverticulosis (pouches in the small intestine)
  • Surgical procedures like Roux-en-Y (gastric bypass surgery)
  • Scar tissue from radiation or surgery
  • Injury to your small intestine
  • Unusual passage (fistula) between two parts of your bowel
  • A buildup of protein called amyloid in your small intestine
  • Blockages in the GI tract

Medical conditions like these can keep your intestines from working the way they should:

Medicines are sometimes at the root of SIBO. These may include:

Symptoms of SIBO can look like those of many other conditions. If you’ve had symptoms that don’t go away, see a gastroenterologist. This type of doctor specializes in the digestive system.

They’ll probably order tests such as:

  • Imaging tests like as X-rays, CT, or MRI to look for physical problems in your intestines
  • Blood tests to check for anemia or a lack of vitamins
  • Stool tests that look for problems like how much fat your body is absorbing
  • Small intestine aspirate and fluid culture. Your doctor passes a long, thin tube called an endoscope through your digestive tract to your small intestine. They take a small sample of the fluid inside and do a lab test called a culture to see what kind of bacteria it has.
  • Hydrogen breath test. First, you drink a sugary beverage. Over the next 3 hours, you breathe into a balloon every 15 minutes. This air is tested to see if it has high levels of hydrogen or methane to suggest SIBO.

To treat SIBO, you need to get your gut bacteria back in balance. That should ease your symptoms and help your body absorb more nutrients from your food.

The treatment might depend on the results of your breath test. If your sample had a lot of hydrogen in it, the main treatment is the antibiotic rifaximin (Xifaxan). If your test showed high levels of methane, you’ll probably take rifaximin plus the antibiotic neomycin (Mycifradin).

Other antibiotics that treat SIBO include:

You might need to take antibiotics for only a week or two, or for a longer time. Your doctor could also switch among several kinds.

SIBO can make it so your body doesn’t absorb enough of certain nutrients like vitamin B12, iron, thiamine, and niacin. Supplements may help.

Some people need surgery if their SIBO stems from a physical problem with their intestine. If this is the case, see your doctor regularly after the operation to check on your digestive health.

If you don’t have SIBO because of an anatomical problem, a simple step is to cut out sugary foods and drinks. This may be all it takes to feel better.

Other diet changes for SIBO include:

  • Quitting foods that seem to make your symptoms worse and waiting 3 days before putting them back on your menu. This way, you’ll know whether a certain food triggers your symptoms.
  • Avoiding fiber supplements as well as any liquid medications (such as cough syrup) that use sugar alcohols for flavor.
  • Avoiding lactose. If your small intestine is damaged, you might lose the ability to digest lactose, the sugar in milk products.
  • A low-FODMAP diet. FODMAP stands for fermentable oligosaccharides, disaccharides, monosaccharides, and polyols. FODMAPs are a type of carbohydrate. But not every carb is a FODMAP. A nutritionist or a doctor experienced in nutrition can help you come up with the right plan.
  • The elemental diet. This is an eating plan that involves special nutritional formulas instead of typical foods. They’re designed to meet your body’s nutritional needs.
  • Prebiotics and probiotics. You can get probiotics in fermented foods like yogurt (look for “live, active cultures” on the label), kefir (a yogurt-based drink), and kimchi (a traditional Korean relish). To get more prebiotics from foods, include lots of fruits, veggies, and whole grains.

If you’re thinking about taking prebiotics or probiotics in supplements, talk with your doctor first to make sure they’re a good choice for you. Foods are always a good first step, since you’ll get lots of other nutrients that are good for you.

Without treatment, SIBO can lead to problems including:

Show Sources


Johns Hopkins Medicine: “Small Intestinal Bacterial Overgrowth (SIBO).”

Cleveland Clinic: “Small Bowel Bacterial Overgrowth.”

University of Virginia Health System: “Patient Education.”

Alimentary Pharmacology and Therapeutics: “Systematic Review With Meta-analysis: The Prevalence of Small Intestinal Bacterial Overgrowth in Inflammatory Bowel Disease.”

Gut and Liver: “Small Intestinal Bacterial Overgrowth and Irritable Bowel Syndrome: A Bridge Between Functional Organic Dichotomy.”

Indian Journal of Medical Research: “Probiotics, Prebiotics & Synbiotics in Small Intestinal Bacterial Overgrowth: Opening Up a New Therapeutic Horizon!”

UpToDate: “Small intestinal bacterial overgrowth: Management.”

American Academy of Nutrition and Dietetics: “Prebiotics and Probiotics: Creating a Healthier You.”

Mayo Clinic: “Small intestinal bacterial overgrowth (SIBO).”

Medscape: “Bacterial Overgrowth Syndrome.”

Gastroenterology & Hepatology: “Small Intestinal Bacterial Overgrowth: A Comprehensive Review.”

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Children’s Hospital of Philadelphia: “Small Bowel Bacterial Overgrowth.”

CHOC Children’s: “Elemental Diet.”


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