6 Signs That SIBO Might be the Root Cause of Your IBS

By Dr. Jill Carnahan, M.D.
Functional Medicine Expert

6 Signs That SIBO Might be the Root Cause of Your IBS. Studies show that over 50% of patients diagnosed with IBS actually have an underlying imbalance called SIBO, or small intestinal bacterial overgrowth. The majority of our gut bacteria should be in the colon. When the bacteria migrate backwards into the small bowel or when there is low stomach acid or poor pancreatic enzyme production, bacteria in the small bowel can overgrow and cause symptoms, such as diarrhea, gas, or bloating.

Six signs you might have SIBO

  1. You notice that fiber worsens your constipation
  2. You notice an improvement in IBS symptoms when taking antibiotics
  3. You feel more gas and bloating when you take probiotics that contain prebiotics
  4. You have celiac or are gluten intolerant and do not have 100% resolution of symptoms on a gluten-free diet
  5. You develop chronic symptoms of gas, bloating, constipation or diarrhea after taking pain medications, like opiates.
  6. Your blood work shows chronically low iron or ferratin with no known cause

Top 6 Symptoms of SIBO

  1. Abdominal bloating and distension
  2. Constipation
  3. Diarrhea
  4. Abdominal pain or discomfort
  5. Acid reflux or heartburn
  6. Excessive gas or belching

How do I know this isn’t just leaky gut?

While SIBO usually manifests with local GI symptoms, a leaky gut will manifest with systemic complaints that affect the immune system. Keep in mind that is is not uncommon to have both SIBO and leaky gut simultaneously. And very often if you have SIBO for a long period of time, you will develop a leaky gut. Here are some systemic signs of a leaky gut:

  • Multiple food sensitivities
  • Skin rashes, acne or rosacea
  • Respiratory symptoms, like asthma
  • Allergic symptoms or increase in seasonal allergies
  • Fatigue
  • Brain fog or poor concentration, especially after meals
  • Any autoimmune disease
  • Joint pain or arthritis
  • Headaches or migraines

Remember SIBO can cause leaky gut syndrome but not everyone with SIBO has leaky gut. About half of the patients diagnosed with SIBO will also have leaky gut. Most of the time if SIBO is treated, leaky gut will heal itself!

10 conditions that may predispose you to have SIBO

  1. Hypochlorhydria (low stomach acid)
  2. Pancreatic insufficiency
  3. Decreased motility in small intestine
  4. Bowel obstruction
  5. Diverticula
  6. Surgical bowel resection or bariatric surgery
  7. Food poisoning (Post infectious IBS)
  8. Nerve damage that affects the GI tract
  9. Drugs, like opiates
  10. Any disease that slows motility (diabetes, hypothyroid)

Other disorders that may be associated with SIBO

  • Rheumatoid arthritis
  • Ankylosing spondylitis
  • Scleroderma
  • Hashimoto’s thyroiditis
  • Rosacea
  • Restless leg syndrome
  • Pancreatic insufficiency
  • Liver disease
  • Diabetes
  • Crohn’s disease
  • Celiac disease
  • Fibromyalgia
  • Kidney failure
  • Liver disease
  • Diverticulosis

How to Diagnose SIBO

• Ask your doctor to order the Lactulose Breath Test (preferred over glucose as it will test the entire small bowel vs. just duodenum)
• You may also need to check a comprehensive stool analysis and urinary organic acids, which may point in the direction of other dysbiosis but are not directly assessing small bowel bacterial overgrowth

How do we treat SIBO?

Diet options

  1. Paleo diet or autoimmune paleo diet
  2. Low FODMAP diet
  3. Specific Carbohydrate Diet
  4. GAPS Diet
  5. Avoid all alcohol
  6. Use caution with probiotics/prebiotics
  7. Use caution with fermented foods as they can increase histamine
  8.  Homemade Elemental Diet by Dr. Siebecker


  1. H2 Predominant SIBO: Xifaxan
  2. Methane Predominant SIBO Xifaxan plus neomycin or tindamax

Dr. Jill’s favorite antimicrobial herbs (call office to order #303-993-7910)

  1. Allimax Pro 
  2. Oil of oregano
  3. Thorne Berberine 500 
  4. Biocidin

Treating SIBO successfully is not always easy and may involve major dietary changes and medication or herbal treatment for an extended period of time. However, getting the balance of your gut microbes healthy will likely prove to be the most important step in regaining your health and vitality! I know it was in my case… if you haven’t read My Story, check it out, here!

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