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You got diagnosed with “IBS.” A label that describes what your gut is doing, not why.
If you’re dealing with abdominal pain, chronic constipation, chronic diarrhea, alternating between the two, gas, bloating, urgency, or the sense that your gut has become the loudest part of your day, this is for you.
And, before your doctor tells you again that this is “just IBS” and hands you a low-FODMAP handout, a fiber supplement, and an antispasmodic prescription, let me gently interrupt that narrative.
IBS is not a root cause diagnosis.
It is what physicians call a “diagnosis of exclusion”.
The standard workup ruled out celiac, ruled out IBD, ruled out obvious structural issues, and when nothing showed up on the standard panels, the label became the answer.
That label does not explain why your gut is doing what it is doing.
It just describes it.
And, most people who leave that appointment then spend years cycling through elimination diets, probiotics, digestive enzymes, low-FODMAP protocols, gut-directed hypnotherapy, peppermint oil capsules, antispasmodics, antidiarrheals, laxatives, neuromodulators like low-dose tricyclics, and now increasingly the newer investigational drugs being studied for IBS specifically.
And, trust me…I get it.
Almost none of my former IBS clients still have IBS symptoms today.
Not because IBS was cured by a specific protocol or supplement stack. Because the label “IBS” was hiding one (or several) of ten specific upstream drivers that nobody screened for.
Here are the ten most common root causes I see in clients who were told they had “IBS” and were told to just live with it.
1. SIBO (Small Intestinal Bacterial Overgrowth)
The single most common driver cluster of what gets labeled IBS.
Bacteria, methanogens, or fungi that belong in your colon (or that should not be present at all) overgrow into the small intestine, where they were not designed to be. They ferment carbohydrates before your body can absorb them, producing gas, bloating, pain, and altered bowel patterns.
The three patterns present slightly differently:
SIBO (bacterial overgrowth) typically presents as bloating, gas, and often IBS-D (diarrhea-predominant) or IBS-M (mixed).
IMO (methanogen overgrowth) typically presents as bloating, constipation-predominant IBS-C, and is driven by methane-producing archaea rather than bacteria.
SIFO (fungal overgrowth) typically presents as bloating, sugar cravings, brain fog, and often coexists with SIBO. Chronic antibiotic exposure and high-sugar diets are common drivers.
An estimated 30-60% of people diagnosed with IBS have SIBO underneath. IMO is increasingly recognized as the specific driver of IBS-C. SIFO is significantly under-tested because standard breath testing does not catch it.
The trio breath test (hydrogen + methane + hydrogen sulfide) is inexpensive and increasingly available. Stool testing catches SIFO. Most people with an IBS label have never been offered either.
2. Low Stomach Acid
Wildly overlooked.
When stomach acid is low (from chronic stress, long-term PPI use, aging, undereating, or years of gentle eating without rebuilding digestive capacity), protein does not break down properly. Bacteria and pathogens survive the stomach environment when they should have been killed. Food sits longer than it should and ferments downstream.
Bloating, gas, and IBS-C symptoms often come from too little acid, not too much.
Which is why so many people with IBS symptoms feel worse on acid blockers.
3. Bile Acid Dysregulation
Bile from the liver + gallbladder is what emulsifies fat, kills incoming pathogens, and drives colon motility.
When bile flow is sluggish (from years of low-fat eating, gallbladder removal, hormonal issues, or liver overload), fats do not break down properly, food sits too long, and downstream fermentation increases.
When bile acid reabsorption is impaired (bile acid malabsorption or BAM), the excess bile in the colon triggers watery diarrhea. This is often labeled IBS-D and never actually screened for.
4. Undiagnosed Parasitic Persistence
Especially in patients who developed IBS symptoms after a foreign trip, food poisoning episode, or specific gut infection.
The medical literature calls this post-infectious IBS. The trigger event is documented. The mechanism (persistent low-grade infection or immune response after a pathogen) is documented. And yet the standard treatment is rarely to look for what is still there.
If your gut symptoms began after a specific event, parasitic persistence deserves consideration.
5. Post-Antibiotic Microbiome Disruption
Antibiotics are sometimes life-saving. They also cause substantial microbial disruption that can take months to years to resolve on its own.
If your IBS symptoms began within a year of a significant antibiotic course, this is likely part of the picture.
6. Chronic HPA Axis Dysregulation
Your enteric nervous system (the “second brain” in your gut) is directly connected to your central nervous system via the vagus nerve. Chronic HPA axis dysregulation affects gut motility, mucosal barrier function, and visceral hypersensitivity.
This is the driver of what gets labeled “IBS-M” (mixed) and “functional dyspepsia” most consistently in my clinical experience.
Fixing the gut without addressing the nervous system underneath produces temporary results at best.
7. Undiagnosed Food Intolerances (Not Just FODMAPs)
Beyond gluten and dairy, there are histamine intolerance, salicylate intolerance, oxalate issues, fructose malabsorption, and lectin sensitivity that all present as “IBS”.
Elimination protocols are frustrating precisely because most people are asked to eliminate the wrong things.
Which is why so many low-FODMAP diets produce partial relief and then plateau.
8. Gut Permeability (Sometimes Called Leaky Gut)
Increased intestinal permeability lets bacterial byproducts (LPS) into circulation, driving systemic inflammation that shows up as bloating, food reactivity, brain fog, fatigue, and skin flares in addition to the gut symptoms.
This is now well-documented in the peer-reviewed literature. It is also rarely tested for in standard gastroenterology workups.
9. Bile Duct or Pancreatic Insufficiency
Sometimes the pancreas is not producing enough digestive enzymes. Sometimes bile ducts are partially obstructed. Sometimes the gallbladder was removed years ago and no one told you that changed how you would digest fat for the rest of your life.
Any of these produce the exact symptom cluster labeled IBS.
10. Mold + Mycotoxin Exposure
A massively under-covered driver.
Chronic mold exposure (from water-damaged homes, workplaces, or environmental sources) produces gut symptoms that mimic IBS almost exactly. Mycotoxins directly disrupt the gut microbiome, damage the mucosal barrier, and drive systemic inflammation.
If your IBS symptoms are worse in specific buildings, environments, or seasons, this deserves consideration.
Why “IBS” Persists
You can eat low-FODMAP, take probiotics daily, run through six elimination diets, and try every gut-directed hypnotherapy app and still be bloated in six months.
Because none of that addresses which of the ten drivers above is actually running your gut.
The IBS label describes the pattern.
It does not identify the driver.
Which is why the standard treatment path (elimination → fiber → antispasmodic → neuromodulator → newer investigational drug) produces partial relief for most people and full relief for very few.
Fix the driver, and the pattern will absolutely resolve.
What Actually Works
The path back to unbroken digestion is a sequence, and the order matters more than any single intervention.
Drainage first. Bile flow, bowel motility, mucosal barrier, and mineral status determine whether anything else you do will land.
Then, proper identification. Get the specific tests you were not offered the first time around, whether this be a breath test for SIBO, a stool test for parasites and pathogens, or a comprehensive digestive panel that includes bile acid markers, elastase, and inflammation markers. Consider mold testing if your history suggests it.
Then, targeted work. Match the intervention to the driver, not the label.
Nervous system work in parallel. Because none of the above lands if the HPA axis is still running the show.
This is the shape of the work.
The specific sequencing for your body is the personalized piece I do with clients.
What Not To Do
Don’t accept “you just have IBS” as an answer that closes the conversation.
Don’t commit to a lifetime of low-FODMAP eating without addressing what is driving the reactivity.
Don’t stack more probiotics and enzymes on top of an untested, congested terrain.
Don’t assume the newer investigational drug being studied for IBS will resolve what the standard drugs have not, especially if the mechanism (visceral hypersensitivity, enteric signaling) is downstream of the actual driver in your specific case.
Don’t spend another five years assuming this is normal.
It’s not.
The Bigger Picture
Almost none of my former “IBS” clients still have IBS symptoms.
Not because IBS was cured by a supplement stack or a specific diet.
Because the label was hiding something specific, and once we found what it was, the symptoms resolved.
If you have been told you have IBS and told to live with it, this is your permission slip to keep asking questions.
The label is a starting point, not an ending.
Take my free Gut Health Diagnostic if you want a real read on what your gut is actually telling you and the best next step for your situation.
If this hit, I would love to know: which of the ten drivers do you suspect might be yours? Have you been offered any of the more specific tests, or has your workup stopped at “just IBS”? Let me know in the comments, I read and reply to every single response.
If you’re ready to address the actual terrain underneath your own IBS label rather than continue cycling through interventions that were not actually designed to address it, I’m currently taking a very limited number of new 1:1 coaching clients heading into August and September. The first step is a 45-minute Client Intake call where we map your full picture and figure out together whether the work is the right fit for where you are. Book your free Client Intake call.
And, if you have any other questions or comments, don’t hesitate to ask me any time in my weekly Q&A in my paid subscriber channel. If you’re not a paid subscriber, sign up below.
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Hi Meghan - really valuable to see more people opening up the conversation around why IBS can feel so complex. Thanks for continuing to bring attention to that experience.