IBS or SIBO? Understanding Why Bloating and Changes in Bowel Habits Can Feel So Similar
By Dr. Irina Chan, Naturopathic Doctor
If you’ve been dealing with ongoing bloating, abdominal discomfort, or unpredictable bowel habits, you may have come across two terms that often get mentioned together: IBS and SIBO.
They can look and feel very similar, which makes it hard to determine which one you may be experiencing. In my practice, understanding the difference is an important first step toward figuring out the right approach for your digestive health.
What Is IBS?
Irritable bowel syndrome, or IBS, is a clinical diagnosis marked by bloating, abdominal pain, and changes in bowel habits, including constipation, diarrhea, or a mix of both. It’s diagnosed using the Rome IV criteria, which look at the pattern and timing of your symptoms rather than a single lab result. That’s because IBS is a functional condition. The digestive tract isn’t working the way it should, even though standard testing doesn’t show any structural or infectious causes. One thing I see often with IBS in particular is a strong connection to stress, and patients frequently tell me their pain eases up after a bowel movement.
What Is SIBO?
Small intestinal bacterial overgrowth, or SIBO, is a measurable increase in bacteria in the small intestine, an area that’s normally home to far fewer bacteria than the colon or large intestine. Research suggests roughly 36-38% of people diagnosed with IBS actually test positive for SIBO.
There are some patterns that tend to point toward SIBO more specifically: bloating that gets progressively worse as the day goes on, symptoms that flare up after fiber or probiotics, excessive burping and gas, bloating that shows up even after just drinking water, bowel urgency, or symptoms that started after a bout of food poisoning or a round of antibiotics. None of these on their own confirm anything, but they’re useful clues worth paying attention to.
Symptoms IBS and SIBO Can Have in Common
Here’s where it gets tricky. Both conditions can show up as bloating and visible distension, abdominal pain or cramping, gas, changes in how often you’re going, and changes in stool form, whether that’s looser, harder, or just inconsistent.
Because there’s so much overlap, it can be difficult to tell IBS and SIBO apart based on symptoms alone.
Why Bloating Alone Cannot Tell You the Cause
Bloating is one of the most common things patients bring to me, and also one of the least specific. It can come from food sensitivities, motility issues, low digestive enzymes, hormonal shifts, stress, or bacterial overgrowth, among other things. Two people can describe nearly identical bloating and be dealing with completely different root causes.
That’s why I don’t rely on bloating by itself to figure out whether someone’s dealing with SIBO or IBS. The timing, the triggers, and what else is going on all matter, and even then, it really needs to be looked at as part of the bigger picture rather than one symptom in isolation.
Can SIBO Cause Constipation or Diarrhea?
It can cause either, and sometimes both, depending on the person. A lot of this comes down to which gases the bacteria are producing. Methane associated overgrowth tends to show up more with constipation, while hydrogen dominant patterns lean more toward diarrhea. This is part of why SIBO can look so different from one person to the next, and why it sometimes gets mistaken for IBS-C or IBS-D.
When Might SIBO Breath Testing Be Considered?
Breath testing is one of the more accessible ways to check for SIBO. It measures hydrogen and methane produced by bacteria after drinking a lactulose solution. I’ll usually consider this when someone already has an IBS diagnosis but is showing specific features that point toward bacterial overgrowth, such as symptoms that match the patterns above, a history of antibiotics or food poisoning right before things started, or simply not improving despite standard IBS management.
To be clear though, not everyone with IBS needs this test. It’s one tool among several, and it comes down to what’s actually going on for that person.
Why Testing Should Be Interpreted Alongside Your Symptoms
A positive result in someone whose symptoms don’t quite fit the picture, or a negative result in someone with a textbook SIBO history, both need context. I look at test results alongside someone’s full symptom history, their diet, medications, and past digestive issues, to determine what is appropriate treatment for them.
What Happens After Digestive Testing?
Once I have results back, the next step is building a plan around what we actually found. Depending on the case, that could mean addressing bacterial overgrowth with antimicrobial herbs, targeting biofilm, working through dietary triggers, supporting motility, healing and repairing the gut lining, and putting steps in place to prevent things from coming back.
Digestive Health Support in Pickering and Ajax
If you feel stuck trying to figure out whether you’re dealing with IBS, SIBO, or something else entirely, working with a naturopathic doctor who focuses on digestive health can help you gain more clarity. We’ll start with a deep dive into your digestive patterns and health history, and look into targeted testing when appropriate, with the goal of understanding what’s happening in your body. When you’re ready, feel free to book a 15-minute discovery call. We can chat about where you’re at and how we can work together to get meaningful, long-term benefits.