Better Me

What is SIBO (Small Intestinal Bacterial Overgrowth)?

Our guts, or intestinal systems, are filled with billions of bacteria known as gut flora. When they play well together, they can help us to digest food and maintain proper immune system functioning.

But there are times when an imbalance in our guts can wreak havoc on our gastrointestinal system. With this imbalance, it can cause a host of problems, such as bloating, abdominal pain, gas and diarrhea—telltale signs of irritable bowel syndrome (IBS) but also a lesser-recognized condition called small intestinal bacterial overgrowth (SIBO).

What is SIBO?

SIBO is a medical condition that occurs when an excessive number of bacteria that usually grows in one part of your digestive tract starts growing in the small intestine. It can cause pain and diarrhea but also more serious complications like malnutrition.

“SIBO is a common cause for IBS,” said Lloyd Perino, MD, a gastroenterologist at Banner Health who specializes in digestive disorders. “It is now thought that up to one-third of patients with IBS really have SIBO.”

Could you be at risk of having SIBO? What signs should you look out for? We met with Dr. Perino to break down the symptoms, causes and treatment options for this digestive condition.

Signs and Symptoms

Because the symptoms of SIBO are very similar to IBS, it can be very challenging to diagnose. Not only that, it can also present itself differently from one person to another. While someone may experience diarrhea, another will experience bloating and constipation.

The signs and symptoms of SIBO include:

  • Gas and/or bloating after a meal
  • Diarrhea
  • Bloating or swollen abdomen
  • Constipation
  • Stomach pain
  • Nausea
  • Malabsorption
  • Unintentional weight loss

While some symptoms like bloating, nausea and diarrhea can be related to several intestinal issues, if you are experiencing persistent diarrhea, rapid weight loss or stomach pains that persist longer than a few days, you’ll want to see your doctor.


“There are a myriad of factors that can cause SIBO, from having certain chronic health conditions like diabetes to surgeries and even age,” Dr. Perino said. “It doesn’t necessarily stand alone."

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

  • Long-term Proton Pump Inhibitor (PPI) Use: Research shows taking a PPI can reduce acid that protects the small bowel from ingested bacteria.\
  • Age: As some people age, they can lose the ability to make gastric acid that helps break down food.
  • Diverticulitis: Small bowel diverticulitis can act as a reservoir for bacteria.
  • Adhesions or Scar Tissue: This can occur as a result of abdominal surgeries or radiation therapy.
  • Ileocecal (IC) Valve: If you lose your IC valve during surgery, bacteria can enter from below.
  • Chronic medical conditions: Certain medical conditions like diabetes, Crohn’s disease and celiac disease can put you at higher risk for developing SIBO.


If you believe you have SIBO, make an appointment with your doctor or a gastroenterologist. In order to diagnose SIBO, your doctor will need to run tests to look at bacterial overgrowth in your small intestine and rule out other problems that may be causing or contributing to your symptoms.

“Currently, there is not an easy, reliable test for SIBO, although a lactulose breath test is usually suggested,” Dr. Perino said.

The lactulose breath test measures levels of hydrogen and methane gas, which would suggest you have SIBO. Doctors do this by having you swallow a drink containing sugar lactulose. Then every 15 minutes for two hours breath samples are collected. This air will be tested to see if it has high levels of hydrogen and methane.


For most people, the initial way to treat SIBO is with a course of antibiotics. Antibiotics most often reduce the number of abnormal bacteria and ease your symptoms.

“The goal for treatment is to get the bacteria under control and this is usually done with antibiotics, such as Flagyl and Xifaxan,” Dr. Perino said. “Although most antibiotics can be used and rotated, these two are the most commonly used to treat SIBO."

Dietary changes may be helpful too, but they may not treat the underlying cause. You can try cutting out sugary foods and drinks or foods that make your symptoms worse. Some doctors recommend a low-FODMAP diet (fermentable oligosaccharides, disaccharides, monosaccharides and polyols), but Dr. Perino recommends speaking with your doctor or a nutritionist who’s knowledgeable about nutrition. “They can tell you what you can eat and how to meet your nutritional needs,” he said.

While antibiotics are the primary treatment method, it’s important to also address any underlying problems that may be contributing to SIBO.


“Unfortunately, treating SIBO takes patience as it usually will come back,” Dr. Perino said. “If we can correct the underlying causes and support proper gut health, you’ll see improvements.”

Schedule an Appointment

If you are experiencing abdominal pain and bloating, diarrhea and/or constipation, schedule an appointment with your primary care physician or a gastroenterologist who specializes in digestive disorders. To find a specialist near you, visit