What is Small Intestine Bacterial Overgrowth (SIBO)?

If you have been diagnosed with Irritable Bowel Syndrome (IBS), chances are that you actually have small intestine bacterial overgrowth (SIBO). Normally, you have small amounts of bacteria present in your small intestine. In SIBO, the bacteria proliferate in your small intestine where they ferment sugars from your food leading to digestive symptoms.

Symptoms of SIBO

  • abdominal pain & cramps
  • bloating
  • burping 
  • gas
  • constipation
  • diarrhea
  • heartburn

What causes bacteria to overgrow?

Bacteria can overgrow in the small intestine under specific conditions. If the pH of the small intestine isn't acidic enough and motility in the gastrointestinal tract is slow, bacteria from the large intestine can colonize the small intestine. Stress, medications, acute gastroenteritis and other medical conditions are the most common factors that decrease motility in the digestive tract. Stress and medications that decrease stomach acid are common factors that cause changes in pH in the small intestine. 

The overgrown bacteria damage the lining of the small intestine. The small intestine is responsible for absorbing the majority of the nutrients from food. When it becomes damaged, this leads to nutrient deficiencies such as anemia. The damage to the small intestine also reduces certain enzymes that are responsible for digesting certain carbohydrates. If we can't digest and absorb our food, the bacteria will do it for us. When bacteria digest carbohydrates, this is called fermentation because they produce gas as a byproduct. The gas leads to bloating and abdominal pain.

Other Health Conditions Caused by SIBO

The damage to the small intestine leads to nutrient deficiencies and immune activation that can cause other symptoms and health conditions:

  • Anemia
  • Food sensitivities
  • Headaches
  • Joint pain
  • Fatigue
  • Eczema
  • Asthma & allergies
  • Depression & mood disorders

Associated Conditions

SIBO is associated with many other diseases, either resulting from that disease or causing that disease:

  • up to 78% of people with IBS have SIBO
  • up to 67% of people with celiac disease have SIBO
  • up to 55% of people with connective tissue disease such as scleroderma have SIBO
  • up to 88% of people with Crohn's have SIBO
  • up to 44% of people with diabetes have SIBO
  • up to 54% of people with hypothyroidism have SIBO
  • up to 81% of people with chronic fatigue syndrome have SIBO
  • up to 20% of people with fibromyalgia have SIBO

Testing for SIBO

The current standard for testing is a 2 hour lactulose breath test. You drink a lactulose solution and take breath samples every 20 minutes for 2 hours. This test can be done at home. It measures the production of hydrogen and methane. If bacteria are overgrown in your small intestine, they will ferment the lactulose to produce hydrogen or methane. An elevation of hydrogen greater than 20 ppm within 90 minutes or an elevation of methane greater than 3 ppm within 120 minutes or both is positive for SIBO. Which gas is elevated depends on the specific bacteria in your small intestine.

An alternative to the breath test, which is not well accepted, is a blood test that essentially assesses for damage to the small intestine. But not many practitioners use this test at this time.

Treating SIBO

SIBO is a very complicated condition to treat and all treatment must be done under a qualified doctor. Do not attempt to treat SIBO on your own. Treating SIBO also takes a very long time as there are several phases of treatment:

  1. Eradication of bacteria (antibiotics or herbal antimicrobials)
  2. Restoration of motility (pharmaceuticals or natural agents)
  3. Restoration of digestive deficiencies (gastric acid, digestive enzymes, bile, GI immunity)
  4. Healing gut lining (herbs and nutrients)
  5. Repopulating healthy bacteria
  6. Preventing recurrence (lifestyle, diet, and natural therapeutics)

Treatment may last 6-12 months. Step 1 can often take several rounds of therapeutics, which may take months. Each additional step may take anywhere from 1-3 months. It is also important to note that all SIBO treatments should be individualized. You may have additional conditions, such as leaky gut or an autoimmune disease, that also require treatment. You may also have parasites, yeast overgrowth, or a large intestine bacterial imbalance that need to be treated as well. So it is important to find a doctor who can work with you holistically to fully address your symptoms.


  1. https://www.ncbi.nlm.nih.gov/pubmed/23957651


I'm Dr. Carly and my mission is to create a health revolution. I believe that another prescription is not the answer. I believe in using natural therapies that go beyond the symptoms. And I believe that doctors should spend way more than 7 minutes with a patient.