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  • Writer's pictureMiriam Wheeler, ND, DHANP

Is It Really Just IBS? When to Consider SIBO Instead

If you've been told your gas, bloating, abdominal pain, diarrhea, or constipation are due to irritable bowel syndrome, it may be time for additional workup and treatment.

woman hunched over on bed in pain

Irritable bowel syndrome (IBS) is one of the most commonly diagnosed digestive issues. It's considered a chronic condition that often flares, or occurs episodically. Often, patients experience periods of feeling relatively normal in terms of digestion, and then they might experience a bout of constipation or diarrhea with abdominal pain and bloating. Menstrual periods, food intolerances or sensitivities, and stress are common triggers for IBS flares.

I treat gut-related issues often in practice. It's not uncommon that I see an association between digestive issues and hormonal imbalances, mood disorders, and even autoimmune conditions. Understanding the root cause of patients' symptoms, and the interconnectedness between their gut health and other concerns/diagnoses is key to being able to successfully treat them as a whole person. While I do sometimes agree with a patient's diagnosis of IBS, it's important to me that we've thoroughly investigated the underlying cause of their symptoms. An accurate diagnosis will dictate what treatments are most indicated and inform the prognosis and management of their condition.

In general, IBS is characterized by chronic abdominal pain or discomfort and changes to stool (both its consistency or how formed it is, and/or its passage, e.g. constipation or diarrhea). Abdominal bloating is also a common symptom of IBS. There are guidelines that are often referred to when diagnosing IBS. The Rome IV criteria states that patients must have experienced symptoms at least one day a week for the past three months, and symptoms must have started at least six months ago. The symptoms can be related to defecation, frequency of bowel movements, and changes in stool appearance. Two out of these three signs must occur with symptoms to meet the criteria.

The five subtypes of IBS are:

  • IBS with constipation (IBS-C): stools are typically hard, in pieces, and difficult to pass, or bowel movements (BMs) feel incomplete and may occur less than once a day

  • IBS with diarrhea (IBS-D): stools tend to be loose or watery, and/or BMs occur more frequently (usually > 3/day)

  • IBS with mixed bowel habits (IBS-M): stool alternates between constipation and diarrhea

  • IBS unclassified (IBS-U): bowel habits cannot be accurately categorized as constipation, diarrhea, or mixed; typically the patient reports that diarrhea and constipation are rare

  • Post-infectious IBS (PI-IBS): the development of IBS after infectious gastroenteritis (aka "food poisoning" or "stomach flu")

While the Rome IV criteria are often referred to when making the diagnosis of IBS, technically IBS is considered a diagnosis of exclusion. This means that all other reasonable diagnoses must first be ruled out through testing, imaging, and/or other means of workup and investigation before the diagnosis of IBS should be made. However, this can be expensive and time consuming. Unfortunately for many patients, it's not uncommon to receive a diagnosis of IBS with minimal or no workup done whatsoever; for many patients, the diagnosis of IBS is made based purely on their symptoms.

The problem with this is, if the diagnosis is wrong, often the treatment is wrong too.

Generally, the conventionally offered treatments for IBS consist of dietary modifications, exercise and other lifestyle changes, stress management, and non-specific medications for symptomatic relief (e.g. laxatives, anti-diarrheals, anti-spasmodics, and even antidepressants). More recently, specific strains of probiotics may be prescribed. Treatments are expected to manage patients' symptoms, but are not curative.

A study published in 2017 in Gut and Liver estimated that perhaps upwards of 78% of patients diagnosed with IBS may have a form of gut dysbiosis known as small intestinal bacterial overgrown (SIBO). [1] Gut dysbiosis refers to an imbalance between the beneficial, protective gut bacteria that reside in our gut and help to keep us quite literally happy and healthy. For a multitude of different reasons, these "good" bacteria can get crowded out with problematic bacteria. When the harmful bacteria become more predominant, and gut motility slows down, SIBO and intestinal methanogen overgrowth (IMO) can occur.

The symptoms of SIBO and IMO look very similar to IBS: abdominal bloating, excess gas, abdominal pain, constipation and/or diarrhea, nausea, food intolerances, and indigestion.

Often, patients report their abdomen is so bloated, they look pregnant. They also often report symptoms are worse after eating, and worse throughout the day. They may notice symptoms improve temporarily when taking a course of antibiotics for a separate health issue, and symptoms might worsen from use of probiotics or fiber supplementation.

There are three main subtypes of intestinal overgrowth, named after the predominant gas produced by the microorganism(s) present:

  • hydrogen-type SIBO: typically causes diarrhea or mixed type

  • hydrogen-sulfide type SIBO: typically causes diarrhea

  • methane-type IMO: typically causes constipation

When I suspect SIBO/IMO in a patient, I will order a breath test to confirm the diagnosis. With SIBO/IMO in particular, it's super important that we identify the specific type of overgrowth as successful treatment is dependent on an accurate diagnosis.

Unlike true IBS, SIBO/IMO can be cured successfully with the correct treatment. Treatment typically consists of eradication (either through specific antibiotics and/or antimicrobial herbs), restoration of normal gut function and motility, and replenishment of beneficial bacteria. It can be a bit of trial and error, but an accurate initial diagnosis through comprehensive breath testing (and occasionally repeat testing to verify eradication of the overgrowth) is key, in my experience.

For my patients, I use TrioSmart, a breath test that tests for all three types of gas (hydrogen, hydrogen sulfide, and methane). The test can be completed by patients in the comfort of their own home, is shipped back to the laboratory, and results are typically received within a week or less. The company bills insurance companies, but also has competitive cash-pay pricing for uninsured patients.

Relapse is not uncommon when treating SIBO/IMO, though I have success in treating cases that were previously recurrent for many years. I work with patients to find an effective and individualized treatment plan that works with their budget and lifestyle, that provides lasting relief. I often include homeopathic treatment along with other therapies, as I have found this yields the fastest symptomatic relief and reduces risk of recurrence.

If you're struggling with IBS-like symptoms, but haven't had much workup to rule out other possible causes, or haven't found a treatment approach that actually works, I'd love to work with you to help ease your suffering. While digestive issues are unfortunately not uncommon, they don't have to be a regular part of your life. Gut health is far too important to ignore and go untreated!


[1] Ghoshal UC, Shukla R, Ghoshal U. Small Intestinal Bacterial Overgrowth and Irritable Bowel Syndrome: A Bridge between Functional Organic Dichotomy. Gut Liver. 2017 Mar 15;11(2):196-208. doi: 10.5009/gnl16126. PMID: 28274108; PMCID: PMC5347643.


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