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Oh Sh!t. I Have IBS.
Understanding IBS More Than a Sensitive Stomach.
Bloating. Abdominal pain. Constipation. Diarrhea. IBS can look different from one person to another.
And while the symptoms are common, the condition itself is more complicated than many people realize.
Medically reviewed by Dr. Ken Brown, Gastroenterologist · Updated October 2026 · Sources
Bloating
Abdominal Pain
Constipation
Diarrhea
What Is IBS?
Start With the Gut.
"There could be two people next to each other. One has constipation, one has diarrhea, and they leave with the same diagnosis."
Irritable bowel syndrome is a recognized digestive disorder involving recurring abdominal pain associated with changes in bowel habits.1
It's classified as a disorder of gut-brain interaction. But that conversation runs mostly one way: much of the signalling travels from the gut to the brain, which is why researchers keep looking closely at what's happening in the gut itself.
IBS doesn't have one single cause or one diagnostic blood test.2 Different factors can contribute to similar symptoms.
Same Diagnosis. Different Experiences.
Some people experience constipation. Others experience diarrhea. Some alternate between the two. Bloating and abdominal discomfort can occur across these patterns.
IBS-C
Constipation-predominant
Constipation is the main pattern. Hard stools, straining, abdominal pain and bloating are common.
IBS-D
Diarrhea-predominant
Loose stools are the main pattern, often with abdominal pain and urgency.
IBS-M
Mixed
Both constipation and diarrhea occur.
IBS-U
Unclassified
Symptoms meet the criteria for IBS but don't fit clearly into the other patterns.
The Microbe Question
Could Your Microbes Be Involved? Possibly.
Research has identified differences in microbial communities and activity in some people with IBS.4 Scientists are investigating whether these differences contribute to symptoms, result from other changes in the gut, or both.
Microbial fermentation can produce gas, while certain microorganisms produce methane, which has been associated with slower intestinal transit and constipation.5,6
But microbes are only one part of the IBS picture.
Similar Symptoms. Different Conditions.
IBS and SIBO.
IBS and small intestinal bacterial overgrowth, or SIBO, can share symptoms.7
Your digestive tract naturally contains microorganisms, but their numbers and composition vary depending on location. The large intestine is home to a dense microbial community.
The small intestine generally contains fewer microorganisms and is where much of your food is digested and nutrients are absorbed.
SIBO occurs when excessive numbers of bacteria are present in the small intestine. This can contribute to bloating, gas, abdominal discomfort and changes in bowel habits.7
Some people diagnosed with IBS also have evidence of microbial overgrowth, but the conditions aren't interchangeable. Understanding the overlap may help clinicians investigate symptoms more carefully.
IBS or SIBO? Sometimes Both.
The relationship remains an active area of research, and SIBO doesn't explain every case of IBS.7
IBS
A symptom pattern
IBS describes a broader pattern of digestive symptoms, diagnosed from recurring abdominal pain and changes in bowel habits.1
SIBO
A microbial finding
SIBO refers to excessive bacterial populations in the small intestine.7
Both, or One
They can overlap
Some people may have both. Others may have IBS without SIBO.
Two-Way Traffic
Let's Talk About Methane.
Certain microorganisms called archaea produce methane. Increased intestinal methane has been associated with constipation and slower movement of material through the gut.5,6
This is often described as intestinal methanogen overgrowth, or IMO. IMO is distinct from SIBO because methane-producing archaea aren't bacteria and may be found throughout the intestinal tract.7
Hydrogen and methane can be measured through breath testing, although these tests have limitations and require clinical interpretation.7
Dr. Ken Brown
Looking Beyond the Label.
Dr. Ken Brown's clinical and research interests include the role of gut microbes in digestive symptoms.
At KBS Research, we're interested in what happens when microbial activity, fermentation and digestive function interact.
A diagnosis can describe what you're experiencing. Research helps us explore why.
When to See a Doctor
Living With IBS-C?
Meet Atrantil.
GI Doctor-Formulated. Polyphenol-Powered.
Atrantil is a GI doctor-formulated supplement containing Quebracho Colorado, Horse Chestnut and Peppermint Leaf.
In Canada, Atrantil is licensed to help relieve symptoms of IBS-C, such as bloating and constipation.
NPN 80083205
Common Questions About IBS
No. IBS-C includes recurring abdominal pain linked to bowel movements, often with bloating. Constipation without that pain pattern is usually considered chronic constipation rather than IBS-C.
There's no single test. IBS is diagnosed from your symptom pattern, and your provider may order tests to rule out other conditions such as celiac disease or inflammatory bowel disease.
Soluble fibre, such as psyllium, is often recommended. Insoluble fibre, such as bran, can make bloating worse for some people.
Yes. Some people have both, and the symptoms overlap. Having one doesn't mean you have the other, which is why testing and a conversation with your provider matter.
SIBO is usually investigated with a breath test that measures hydrogen and methane. Results need to be interpreted by a healthcare professional.
No. Atrantil is licensed in Canada to help relieve symptoms of IBS-C, such as bloating and constipation. Talk to your provider about SIBO testing and treatment.
Atrantil is licensed by Health Canada (NPN 80083205) to help relieve symptoms of irritable bowel syndrome with constipation (IBS-C), such as bloating and constipation.
References
This page is for education and isn't a substitute for advice from your healthcare provider.
1
Lacy BE, Mearin F, Chang L, et al. Bowel disorders (Rome IV). Gastroenterology. 2016;150(6):1393–1407. PubMed ↗
2
Moayyedi P, Andrews CN, MacQueen G, et al. Canadian Association of Gastroenterology clinical practice guideline for the management of irritable bowel syndrome (IBS). J Can Assoc Gastroenterol. 2019;2(1):6–29. Free full text (PMC) ↗
3
Lacy BE, Pimentel M, Brenner DM, et al. ACG clinical guideline: management of irritable bowel syndrome. Am J Gastroenterol. 2021;116(1):17–44. PubMed ↗
4
Pittayanon R, Lau JT, Yuan Y, et al. Gut microbiota in patients with irritable bowel syndrome: a systematic review. Gastroenterology. 2019;157(1):97–108. PubMed ↗
5
Pimentel M, Lin HC, Enayati P, et al. Methane, a gas produced by enteric bacteria, slows intestinal transit and augments small intestinal contractile activity. Am J Physiol Gastrointest Liver Physiol. 2006;290(6):G1089–G1095. DOI ↗
6
Triantafyllou K, Chang C, Pimentel M. Methanogens, methane and gastrointestinal motility. J Neurogastroenterol Motil. 2014;20(1):31–40. Free full text ↗
7
Pimentel M, Saad RJ, Long MD, Rao SSC. ACG clinical guideline: small intestinal bacterial overgrowth. Am J Gastroenterol. 2020;115(2):165–178. PubMed ↗