What Is SIBO?

Small intestinal bacteria overgrowth (SIBO) is exactly what it sounds like: too much bacteria in the 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 sometimes lifestyle changes are all it takes.


SIBO usually starts when the small intestine doesn’t move food along well enough. This lets 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, and then you’ve got an imbalance that could cause SIBO symptoms.


Early signs are pain in your abdomen, queasiness, fatigue, feeling bloated, passing a lot of gas, and diarrhea or constipation. Many things can cause those problems, so you can’t know that it’s SIBO just based on how you feel.

If you have SIBO and it worsens, your small intestine might not absorb enough food or nutrients. This could lead to weight loss or anemia, with your body not getting enough fuel or iron.

Risk Factors

Things that can make you more likely to develop SIBO include:

Age. Older adults are more likely to have SIBO because they may make less of the gastric acid that breaks down food and are more likely to have diverticulosis.

Anatomy. You may have a small intestine with an unusual shape. Differences in the structure or anatomy of your gut can make food move more slowly than normal and allow bacteria to grow. These may stem from diverticulosis (pouches in the small intestine), procedures like Roux-en-Y gastric bypass surgery, scar tissue from radiation or abdominal surgery, or a buildup of protein called amyloid in your small intestine. Blockages in the GI tract can cause SIBO, too.

Chronic diseases such as diabetes, lupus, and connective tissue disorders like scleroderma can keep your small intestine from working right. An immune system weakened by HIV, immunoglobulin A deficiency, or other reasons can let too much bacteria grow where it shouldn’t.

SIBO seems to be particularly common in people with inflammatory bowel disease such as Crohn’s disease and ulcerative colitis.

Medicines are sometimes at the root of SIBO. Narcotics can slow things down, as can drugs that treat irritable bowel syndrome. Proton pump inhibitors that curb acid in your stomach and antibiotics that affect the bacteria living in your intestines can lead to SIBO.



If you’ve had SIBO-like symptoms that don’t go away, see a gastroenterologist. This type of doctor specializes in the digestive system.

At your appointment, you’ll probably take a lactulose breath test. First, you’ll drink a sugary beverage. Then, over the next 3 hours, you will breathe into a balloon every 15 minutes. This air will be tested to see if it has high levels of hydrogen or methane to suggest SIBO.


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

The treatment you’ll get depends the results of the breath test you took. If your sample had a lot of hydrogen in it, the main treatment is the antibiotic rifaximin. If your test showed high levels of methane, you’ll likely take rifaximin plus the antibiotic neomycin.

It’s rare, but some people may need surgery if their SIBO stems from a problem with their intestine’s structure. If this causes your SIBO, you’ll need to see your doctor regularly after the operation to check on your digestive health.

Lifestyle Changes to Help

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. You can also try quitting foods that seem to make your symptoms worse, then wait 3 days before bringing them back on your menu. This way, you’ll know whether a certain food triggers your symptoms. And avoid taking fiber supplements as well as any liquid medications (such as cough syrup) that use sugar alcohols for flavor.

Your doctor may recommend a low-FODMAP diet. FODMAPs are a type of carbohydrate (FODMAP stands for fermentable oligosaccharides, disaccharides, monosaccharides, and polyols.). Not every carb is a FODMAP. You’ll want to talk to a nutritionist or a doctor who’s knowledgeable about nutrition so you can know what you can eat and how to meet your nutritional needs on this plan.

You might want to ask your doctor whether prebiotics and probiotics could help. 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.

WebMD Medical Reference Reviewed by Jennifer Robinson, MD on April 18, 2019



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