Small Intestinal Bacterial Overgrowth (SIBO): What to Know

Medically reviewed by Kumkum S. Patel MD, MPH

Small intestinal bacterial overgrowth (SIBO) is a medical condition in which excess bacteria grow in your small intestine. This can result in bloating, abdominal pain, flatulence, and altered bowel habits, especially diarrhea. In more severe cases it can cause malnutrition.

This article discusses SIBO symptoms, causes, testing, and treatment.

<p>ingwervanille / Getty Images</p>

ingwervanille / Getty Images

Small Intestinal Bacterial Overgrowth (SIBO) Symptoms

SIBO symptoms and their severity can vary from person to person. You might experience some, but not all, of the following:

  • Abdominal pain

  • Belching

  • Bloating or sense of abdominal fullness

  • Constipation (less common than diarrhea)

  • Diarrhea

  • Flatulence

  • Nausea

  • Unusual stool (e.g., extra smelly or with fatty globs or mucous)

What Causes SIBO?

Typically, your small intestine contains a relatively small number of bacteria compared to your large intestine. In SIBO, something goes wrong, and more bacteria start growing in your small intestine, leading to symptoms.

Some factors that may contribute to increased small intestine bacteria growth include:

  • A malfunctioning valve between the small and large intestine

  • Reduced stomach acid (e.g., from surgery or medications)

  • Slowed movement of food through the small intestine (e.g., from a problem with the intestinal muscles or nerves

People with certain medical conditions, such as those listed below, are more likely to develop SIBO:

The risk of SIBO also tends to increase with age.

Is There a SIBO Test?

Healthcare providers can’t diagnose SIBO just based on your health history or standard blood tests. Clinicians are still working to determine the best way to diagnose SIBO reliably while also weighing the potential disadvantages of different methods.

Small Bowel Endoscopy

Scientists first began describing and diagnosing SIBO by taking bacteria samples from the small intestine and testing to see what bacteria were present. But this requires an endoscopy, an invasive test in which a thin tube is inserted down your throat to your small intestines to get the sample.

Sometimes called jejunal aspiration, this method is still considered the diagnostic gold standard by many, but it’s difficult to perform, invasive, and expensive.

Breath Testing

Healthcare providers use the breath testing method to diagnose SIBO. Using the breath testing method, a healthcare provider measures your exhaled breath for gasses produced by bacteria in the small intestine. If high amounts of the gasses are present, you may have SIBO.

In the past, many clinicians often just measured the amount of hydrogen gas in the breath. However, more recently, many have begun measuring methane gas, too. The devices used for the test can detect and measure hydrogen and methane at the same time, avoiding the need for separate testing.

Glucose vs. Lactulose Breath Testing

Before hydrogen and methane breath testing, you will drink a solution containing a lot of glucose or lactulose, two different carbohydrates. Lactulose testing may require a more extended testing period (three to four hours) compared to glucose (1.5 to two hours).

Tests using glucose may be a bit more reliable than tests using lactulose. However, some people criticize both kinds of breath testing since these tests can miss a lot of people who do have SIBO.

You may get more reliable results if you carefully follow your healthcare provider's protocols before testing. This involves avoiding certain medications in the weeks before and following food requirements the day before.

Other Tests

Sometimes, complementary tests can help providers more accurately diagnose SIBO. Other tests include:

  • Breath testing of fructose and lactulose: These tests don’t pick up SIBO but can identify intolerance to fructose or lactulose, which are possible alternative causes of symptoms.

  • Hydrogen sulfide breath tests: These tests work like other breath tests for hydrogen or methane.

  • Transit time tests: These imaging tests use an X-ray and special dye to show how quickly food is moving through the body.

Sometimes, healthcare providers use antibiotic treatment as a potential test, even if the diagnosis isn’t obvious. If symptoms improve afterward, they may make a retroactive diagnosis.

Learn More: How to Test for Small Intestinal Bacterial Overgrowth (SIBO)

SIBO Treatment Options

The best treatment and management for SIBO is somewhat controversial. To date, the Food and Drug Administration (FDA) has not approved a SIBO-specific treatment.


Antibiotics can help treat bacteria overgrowth present in SIBO. Xifaxan (rifaximin) is the most studied, and it may be better than other antibiotics in preserving healthy bacteria in the large intestine while simultaneously killing less healthy bacteria in the small intestine.

Sometimes, healthcare providers use other agents, like Cipro XR (ciprofloxacin) or Flagyl (metronidazole), especially if symptoms don’t resolve with single antibiotics. People whose SIBO is caused by archaea instead of bacteria may need unique antibiotic treatment combinations, such as Xifaxan (rifaximin) plus neomycin.

However, around 40% of people diagnosed with SIBO have symptoms that don’t resolve with antibiotics.

Using Complementary Approaches

Some people also benefit from the perspective of a complementary healthcare provider, who may provide additional recommendations for nonantibiotic approaches.


Many people are interested in whether dietary changes might help with SIBO. Although scientists haven’t identified anything conclusive, some people have reported relief when they change their diet.

One of the most popular diets for SIBO is the low FODMAP diet (low fermentable oligosaccharides, disaccharides, monosaccharides, and polyols diet). The FODMAP diet reduces the kinds of carbohydrates that bacteria can easily consume, and it’s been used by people with IBS with some success.

However, the diet is very restrictive, so some people find it hard to follow. It may be a helpful tool during a SIBO flare.

Some people also try gluten-free diets for SIBO, but there isn’t convincing evidence that this helps most people. (The low FODMAP diet is low in gluten but is not necessarily gluten-free.)

Another approach is the elemental diet, which contains predigested nutrients you may take as liquids. Some evidence shows this approach is helpful for some people, but it usually isn’t used for more than a few weeks.

Can Probiotics Help Treat SIBO?

The use of probiotics in SIBO is under debate due to a lack of definitive information from extensive scientific studies.

One meta-analysis of multiple studies found that probiotics helped reduce small intestine bacteria while reducing symptoms. However, one study found that probiotics may worsen symptoms like gas and bloating in some people.

If you choose probiotics, slowly incorporate them into your routine and see how your body responds. You might want to try fermented foods that naturally contain probiotics, like yogurt.

Managing Stress

The relationship between stress and gastrointestinal disorders is complex. Scientists are beginning to understand how the brain and nervous system are involved in disorders such as IBS and SIBO.

Stress can directly affect how quickly food moves through the digestive tract. Exercising, talking with a trusted friend or therapist, practicing spirituality, using your creativity, or doing other activities you enjoy may help you manage your stress and potentially decrease SIBO symptoms.

How to Manage SIBO and Prevent Flares

Around 45% of people with SIBO experience symptom relapse within nine months of treatment. Unfortunately, it’s challenging to know the best ways to manage SIBO and prevent such flares; it may require some trial and error. Here are some strategies to consider:

  • Avoid snacking before bed and wait several hours before eating again after a meal.

  • Avoid trigger foods.

  • Consult a healthcare provider about medications that may be worsening SIBO symptoms.

  • Seek treatment for an underlying condition related to SIBO.

  • Talk to a healthcare provider about medications to keep things moving through your digestive tract, such as Prepulsid (cisapride), though this technique isn’t proven.

  • Try another round or a different type of antibiotic.

Learn More: SIBO Treatment: Antibiotics and Diet Changes to Try

Potential Complications of SIBO

If you start to have symptoms from SIBO, it’s essential to get timely medical attention and support. Living with symptoms of SIBO can feel personally debilitating and impact your quality of life.

If severe and if not treated, long-term SIBO can lead to poor absorption in the small intestine that causes nutritional deficiencies, weight loss, and stunted growth in children.

In severe and prolonged situations, deficiencies in various vitamins and minerals like vitamins A, D, K, and B12 from SIBO might predispose you to the following conditions:

  • Anemia with fatigue

  • Easy bruising

  • Impaired immunity

  • Neurological issues, like tingling in your legs

  • Night blindness

  • Skin ulcers

  • Weakened bones due to osteoporosis (a decrease in bone mineral density and bone mass)

People with nutritional deficiencies from SIBO may need to take additional dietary vitamins and minerals, at least temporarily.


SIBO is a medical condition in which your small intestine is overgrown with too many bacteria, causing symptoms like abdominal pain and bloating. It is associated with medical conditions like irritable bowel syndrome, among others.

Talk to a healthcare provider if you are having symptoms, which might be SIBO. Getting a proper diagnosis can help you decrease your symptoms and may help you reduce the chances of long-term complications.

Read the original article on Verywell Health.