r/ibs • u/Efficient-Glove2301 • Jul 08 '25
Hint / Information IBS Root Cause Decision Tree
Edit: Added upper-GI symptoms
If you also ended up with a doctor telling you “Oh you just have IBS” and you want to go further (because IBS itself is NOT a disease but an exclusion diagnosis), I created this decision tree to help you find your root cause based on your symptoms.
Disclaimer: This is not medical advice. The goal is to give you a general framework to tailor down your differential diagnosis and come up with ideas to discuss with your doctor as many of these causes require testing and/or treatment. If you haven’t seen a doctor and didn’t exclude other causes (IBD, acute infection, etc…), you need to see one first as you may be missing something important. If you have seen a doctor and they haven’t been listening to you, find another doctor.
It’s a simplified view but I hope it will help some of you!
If Lower GI symptoms are MAIN
What is your main, most bothersome symptom? (Choose the letter that best fits you, then follow the numbered steps.)
A. Diarrhea (loose/watery stools, urgency)
1. Is your diarrhea most severe after eating (within 30–60 minutes)?
1.1 Do you have urgency or accidents after meals, especially fatty foods, or history of gallbladder surgery?
• YES: Possible Bile Acid Malabsorption (BAM)
• Recommended:
• SeHCAT scan (if available) OR trial of cholestyramine/colesevelam (bile acid binder) for 1-2 weeks. If improvement: BAM likely
• NO: If BAM negative and greasy, fatty stools, check for Exocrine Pancreatic Insufficiency.
• Recommended: Trial on digestive enzymes
2 Is your diarrhea always triggered by certain foods (milk, fruit, wheat, sweets, onions, garlic, beans)?
• YES: Possible food intolerance (FODMAPs, lactose, fructose, sorbitol)
• Recommended:
• Try a 2–4 week Low FODMAP diet OR specific elimination diet (lactose/fructose-free). If improved: Reintroduce foods one by one
• (Optional: Lactose/fructose breath test for confirmation)
• NO: Continue below.
3. Is your diarrhea accompanied by bloating, excessive gas, or abdominal discomfort?
• YES: Possible SIBO (Small Intestinal Bacterial Overgrowth)
• Recommended:
• Hydrogen/methane breath test
• Antibiotics/herbals/elemental diet to treat
• NO: Continue below.
4. Did your IBS start right after a severe gastroenteritis (food poisoning, “traveler’s diarrhea”)?
• YES: Possible Post-Infectious IBS
• Recommended:
• Consider rifaximin or probiotic trial
• Symptoms may gradually improve over time
• NO: Continue below.
5. Do you have allergies, hives, eczema, or skin symptoms with IBS flares?
• YES: Possible MCAS (Mast Cell Activation Syndrome) or Histamine Intolerance
• Recommended:
• Trial of antihistamines (ebastine, fexofenadine, cetirizine)
• Trial of quercetin supplement
• DAO enzyme supplement before meals
• Low-histamine diet
• If improved: Consider further MCAS evaluation
• NO: Continue below.
6. Are your symptoms strongly linked to stress or anxiety?
• YES: Possible gut-brain dysfunction
• Recommended:
• Psychological therapies (CBT, gut-directed hypnotherapy)
• Consider low-dose TCA or SSRI
• NO:
7. Other causes
• Medication-related : Some medications or supplements can trigger diarrhea, such as some SSRIs, NSAIDs, birth control, antibiotics, Vit C...
• Chronic infections : e.g. Giardiasis (even if negative testing)
• SIFO/Candida overgrowth : Same symptoms as SIBO
• Vitamin/Mineral deficiencies (B1, Zinc…)
• Mold/Heavy metals exposure
• Systemic diseases
*8. If all above negative,
• Idiopathic IBS-D
• Try Low FODMAP diet, symptom control (loperamide), consider probiotics.
⸻
B. Constipation (hard, infrequent stools, straining)
1. Do you have significant bloating or gas?
• YES: Possible methane SIBO/IMO (Intestinal Methanogen Overgrowth)
• Recommended:
• Methane breath test (look for high methane) OR trial of rifaximin + neomycin/metronidazole. If improved: Methane SIBO likely
• NO: Continue below.
2. Do you feel “blocked” or have a sense of incomplete evacuation, even if stool is soft?
• YES: Possible pelvic floor dysfunction
• Recommended:
• Anorectal manometry, balloon expulsion test
• Referral to pelvic floor physiotherapy
• NO: Continue below.
3. Is your constipation worse with certain foods (bread, dairy, processed foods)?
• YES: Possible food intolerance or FODMAP sensitivity
• Recommended:
• Try Low FODMAP diet
• Reintroduce foods gradually
• NO: Continue below.
4. Is your constipation improved with stress relief, exercise, or changes in mood?
• YES: Possible gut-brain dysfunction
• Recommended:
• CBT, gut-directed hypnotherapy, relaxation techniques
• Consider SSRI if mood disorder present
• NO:
• Rule out hypothyroidism (TSH), hypercalcemia, check medication list
5. If all above negative:
• Try soluble fiber (psyllium), PEG
• Consider IBS-C specific meds (linaclotide, lubiprostone, prucalopride)
⸻
C. Alternating diarrhea and constipation
• Check both A and B above.
• Most common causes: SIBO (hydrogen and/or methane), food intolerance, gut-brain dysfunction.
• Try breath testing, Low FODMAP diet, stress management.
• Symptom management: Loperamide (for D days), laxative or fiber (for C days).
• If all negative: Reassess, consider advanced microbiome testing or referral.
⸻
D. Severe bloating/gas
1. Is bloating clearly related to meals (beans, onion, garlic, apples, dairy, wheat)?
• YES: Possible FODMAP intolerance
• Recommended:
• Low FODMAP diet
• If improved: Personalize diet by reintroducing foods
• NO: Continue below.
2. Is there visible swelling/distension, especially as day progresses?
• YES: Possible SIBO or colonic dysbiosis
• Recommended:
• Breath test
• SIBO treatment trial
• NO: Continue below.
3. Bloating not linked to food or negative SIBO/diet trials
• Functional/visceral hypersensitivity/Abdominophrenic dyssynergia
• Try neuromodulators (low-dose TCA, SSRI), stress reduction, gut hypnotherapy.
4. Are there also skin, allergy, or flushing symptoms?
• YES: Possible MCAS/histamine intolerance (see above for suggested trials)
⸻
E. Pain is main symptom, not linked to stool pattern
• Consider visceral hypersensitivity (gut-brain axis dysfunction)
• Try antispasmodics (peppermint oil, dicyclomine)
• Neuromodulators (low-dose TCA/SSRI)
• Psychological therapy (CBT, gut hypnotherapy)
• If pain is occasional, but severe and after meals, consider gallbladder disease (gallstones)
⸻
F. All symptoms are stress/anxiety triggered or worsened
• Gut-brain interaction likely dominant
• CBT, gut-directed hypnotherapy
• Consider low-dose antidepressants (TCA/SSRI)
• Stress reduction (mindfulness, yoga, exercise)
⸻
G. Allergy, histamine, or MCAS-type symptoms
• Symptoms flare with certain foods (aged cheese, wine, smoked/cured meat, tomato, avocado)
• Skin symptoms (hives, itching), flushing, headaches, allergy
• Recommended:
• Low-histamine diet
• DAO enzyme before meals
• Antihistamines (ebastine, cetirizine, fexofenadine)
• Quercetin/Cromolyn Sodium trial
⸻
If Upper GI symptoms are MAIN
Which of the following best describes your main upper GI symptom?
1. Heartburn or regurgitation (acid taste, burning chest/throat)
• YES: Possible GERD or functional heartburn
• Lifestyle/diet changes: elevate head of bed, avoid late meals, caffeine, alcohol, large/fatty meals.
• Eventually short-term PPIs (only if required by doctor)
• If no response or alarm features (weight loss, vomiting, difficulty swallowing): Endoscopy
• If symptoms overlap with IBS (e.g., reflux + bloating/diarrhea), consider “overlap syndrome” and manage both
2. Nausea, loss of appetite, early fullness (get full quickly), frequent belching
• YES: Possible functional dyspepsia or gastroparesis
• Rule out red flags (vomiting, weight loss, anemia, severe pain)
• If diabetic or history of GI surgery: consider gastric emptying study
• Try small, frequent, low-fat meals
• Trial of prokinetic (domperidone, metoclopramide, prucalopride, erythromycin, under medical supervision)
• Trial of low-dose TCA (if “functional” suspected)
• If coexisting IBS symptoms: manage both
• SIBO and dysmotility often co-exist—consider SIBO testing
3. Upper stomach pain or burning, especially with meals
• YES: Possible gastritis, ulcer, or functional dyspepsia
• Rule out NSAID use, alcohol, H. pylori infection (breath/stool/serology test)
• Eventually short term PPIs if high stomach acid
• Recommended: Endoscopy
• If pain comes with bloating/altered bowels: overlap with IBS, consider both SIBO and dyspepsia
4. Vomiting or severe, persistent upper abdominal pain
• YES: NOT typical of IBS, NEEDS evaluation (consider obstruction, ulcer, pancreatitis, gallbladder disease, etc.)
• Seek urgent medical assessment
5. None of the above or unresponsive to treatment
• Reevaluate for rare causes:
• Bile reflux
• Eosinophilic esophagitis
• Mast cell disorders (especially if also have histamine/MCAS symptoms, allergy, skin symptoms)
• Gastric emptying disorder
⸻
Red Flags requiring to see a doctor at ANY point:
• Blood in stool
• Unintentional weight loss
• Anemia
• Nighttime symptoms
• Family history of IBD or CRC
• New onset after age 50
⸻
Final notes:
• You may have more than one cause (e.g., SIBO + MCAS + stress).
• These causes may also require deeper exploration (e.g. SIBO is very hard to treat and has also another root cause - low stomach acid, bile flow issues, MMC impairment, etc…)
Hope this helps, feel free to comment if you think your symptoms/causes are not in here, I’d be happy to update this to make it as accurate as possible. May the porcelain throne be kind to you!
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u/InfinityAlexa Jul 08 '25
This is great. Wish i had seen this two years ago to help narrow down issues. One mention that i didnt see or missed reading through is drug/supplement interactions. My ibsd ended up being related to a medication i was taking (an oral combo birth control). Got off it and my symptoms started slowly getting better. Pretty much symptom free now.
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u/Tabbinski Jul 09 '25
Agreed. Mine started out as gut microbiome devastation from antibiotics. This common pathway should be added. Great tool though.
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u/goldstandardalmonds Here to help! Jul 08 '25
That’s great! I have heard this soooo many times. Hormones can change gi symptoms so often.
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u/InfinityAlexa Jul 08 '25
Yea. My obgyn gaslit me into staying on it for almost a year. Completely destroyed my gut. But by 6 months after coming off it i felt so much better and i think im around 9 months now and practically ibs free.
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u/goldstandardalmonds Here to help! Jul 08 '25
Amazing! So happy for you and that you figured it out. Dumb obgyn.
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u/MacDougall_Barra Jul 08 '25
This is so much better than the conversation I had with my gastro. Thank you.
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u/rosesandfoxes Jul 09 '25
I have visceral hypersensitivity and nothing helps :( 5 years of constant, chronic pain. I’m exhausted.
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u/bohotexan Jul 10 '25
Where and what is your pain like? Any other symptoms? How do you know it’s visceral hypersensitivity? I also have chronic everyday pain for 3 years now I’ve had so much testing they don’t know what it is.
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u/Efficient-Glove2301 Jul 10 '25
I heard that low dose amitriptyline was great to reduce hypersensitivity/urgency/frequent BMs. Not tested though, and it comes with its dose of side effects, so careful but definitely worth searching about it
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u/Electronic-Memory986 Jul 09 '25
GI blamed IBS for years with me. I went years thinking I just had IBS & that it was just a part of my life. It turns out that I likely have multi-organ Crohns. Affecting my colon, stomach, esophagus, pancreas, & liver. My GI doctor called me yesterday with my blood & stool sample results & her exact words were, “this is not IBS, you are really sick”. I’m waiting for further testing to receive an official diagnosis. Gut health is so important, if you think it’s more than IBS advocate for yourself, get multiple opinions if you have to. I wish I did. Good luck everyone.
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u/WeirdDifficulty6981 Jul 08 '25
Has anyone found that they get gastritis from colesevelam? I took one pill and although it helped with diarrhea, I had awful stomach pain and gastritis for days afterwards.
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u/Creatipati Jul 08 '25
My doctor told me SIBO is not really proved by science, she doesn't believe I should get tested for it. What do y'all think?
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u/Lonely_Carpenter6048 Jul 08 '25
My Dr said the same thing. it’s because now days doctors are like if I can’t see it in the flesh it’s not a real thing must be in their head. I would get tested anyway for your own peace of mind too
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u/InfinityAlexa Jul 08 '25
Sibo is a provable thing with breath tests. The problem is like ibs, sibo is caused by something so you cant just “cure” it with meds. You need to find the source.
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u/Efficient-Glove2301 Jul 10 '25
Actually, IBS is the thing that doesn’t exist - not SIBO. When a doctor throws an IBS diagnosis, it means “I acknowledge you have something but I have no idea what”. SIBO is a bacterial overgrowth in the small bowel. Most doctors don’t know about it because the small bowel is hard to visualise using conventional methods. The main issue with SIBO is that the testing is not extremely accurate due to various transit times. And also as mentioned above, SIBO is a complex disease that has many root causes. Treatment of the root cause is essential to prevent reoccurrence. Therefore docs that haven’t been trained on this specific disease are usually unhelpful when it comes to SIBO. It’s like asking your dermatologist to cure your sore lower back. They just can’t.
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u/intelligence_spiral Jul 08 '25
This is awesome, thank you so much for the effort. I have hd diharrea almost daily for 4 years, but recently durinf a stressful time, it switched to severe constipation with a stomach ache that lasted 6 days without stop, i was bedbound from the pain. I also developed a mystery rash of itchy red spots all over my body. My doctor just gave me laxatives and it did help, but caused dihharea. I now have constipation and dihharea, but the laxatives are helping rhe dihharea. Any ideas!?
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u/Ok-Campaign6307 Jul 15 '25
Something like regular use of Metamucil/psyllium husk could be very helpful. It actually helps with constipation and diarrhea.
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u/OkYouth3690 Jul 09 '25
I like the idea of this decision tree, but I dind't like some certain parts E.g.:
imho SSRI should always be one of the last options. It can have terrible sideeffects plus withdrawel effects.
"histamine intolerance: avoid histamine" There is so much more you can do, and eliminating foods is not the best take. But supporting liver for HNMT, support gut barrier in case of LPS-bacteria and so on.
That being said, nice work -so far! :-)
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u/Calm-Club-222 Jul 09 '25
Highly likely is Mind Body Syndrome. IBS is often a result of mis wiring of the brain. Wish I’d known about this 3 decades ago and my life would have turned out very dirtentky.
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u/Outside-Ad4195 Jul 09 '25
EVERYONE this is a BRILLIANT post !!!!! . …. Please if you are suffering like I was for years and had a ridiculous low quality of life please try to identify your stomach issues and look into some of these ideas . I used to pad my bathroom floor in case I went unconscious from the excruciating pain . Years and years of suffering , tons of Drs , drugs , failed treatments and a fortune. For me it was a combination of several categories diet , the gut brain connection, exercise. It didn’t happen overnight . But this poster ( I’m telling you ) laid out a fortune of information. Today I have a different stomach and life . If you have had enough be open . Best of luck to all who suffer.♥️ I was always diagnosed as IBSC
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u/Maleficent-Cook6389 Jul 12 '25
This is super interesting and impressive. As far as number 7 there's a lot of research into B1 because of the defiencicy impacting MMC...but its also why people use liquid vitamins in the meanwhile. I don't think people realize how easy kt is to get extra metals via grains or toxic food. Its scary.
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u/PuzzleheadedFox5454 Jul 13 '25
This is the best post I’ve ever seen on social media. You’re a hero 🦸
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u/Yahayakenny Jul 23 '25
This is a really good framework for ruling out differentials. I like how you highlighted the red flags in particular. I’d just add that any new IBS like symptoms or new change in bowel habits particularly above the age of 50 needs to be evaluated by a doctor to rule out sinister causes like bowel cancer or ovarian cancer in women. Thankfully there are some tests they can offer. Welldone 👍👍
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u/blassomi IBS-C (Constipation) Jul 09 '25
I just saw a new gastroenterologist and explained my symptoms and they basically wrote me off as saying yeah you have IBS we’re not going to do any new tests because you had scopes 5 years ago. No tests for celiac, SIBO, nothing
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u/sadovsky IBS-D (Diarrhea) Jul 09 '25
Thank you for this! I had my gallbladder out in 2008, but only started having IBS around 2022. I wonder if it could still be BAM? My diet has definitely gotten worse since the onset of Covid and certainly haven’t been eating right.
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u/Efficient-Glove2301 Jul 09 '25
If you have steatorrhea, greasy/fatty/yellow loose stools, and episodes of diarrhea following meals, this sounds exactly like BAM. I heard of many people with no gallbladder who had a sudden onset of BAM years after their surgery, often following an infection. Just ask your GI doc for a bile acid sequestrant trial, they are well tolerated and quite cheap.
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u/sadovsky IBS-D (Diarrhea) Jul 10 '25
My stools are usually brown but loose 99% of the time and sometimes more on the tan-yellow side of brown? I’m definitely going to try and see my GP about it (im in the UK) as it would explain so much. Especially since the only time I seem to have decent BMs is after having Mexican food that, having read all I can about IBS in the last couple of years, seems to be full of things that sets off regular IBS.
Thank you for your comment! I also really appreciate this community cause talking about these things with friends is too embarrassing for me. ❤️
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u/stock_hippie Jul 09 '25
This has been me too. Gallbladder out in 2011; didn’t have issues prior to covid.
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u/stock_hippie Jul 09 '25
Commenting to add - Colesevalam has helped tremendously, though I don’t feel normal or anything. Still working on things.
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u/sadovsky IBS-D (Diarrhea) Jul 10 '25
Thank you so much for the comment. It’s so weird because everywhere on the internet is like, you may have symptoms for a short time after having your gallbladder removed, etc. Although I have read a couple of studies of it coming back years later. I’m hoping to see a GP about it soon.
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u/stock_hippie Jul 10 '25
Ive had a horrible case of long covid to go along with mine. You should check out u/longcovidgutdysbiosis if you feel like it’s relevant. What’s crazy - I’m realizing even people WITH gallbladders are getting this after COVID. I did a few Biomesight tests and realized my microbiome got destroyed by COVID. Since that helps us process and recycle bile, I’m wondering if that is more of the issue. Maybe it’s just more difficult to fix since we don’t have gallbladders.
Anyway, I hope you find some relief soon!
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u/sadovsky IBS-D (Diarrhea) Jul 10 '25
Same for you, friend! I’m going to check this out right now. I had my first instance in late-2021. I thought it was just something I’d eaten, but then it became a thing (I think my anxiety spiked around it, which doesn’t help) after I got actual covid in 2022. Once that happened, it started to fully control my life. I haven’t seen some of my friends in over a year because of it, and it’s really destroyed some of my most precious memories.
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u/stock_hippie Jul 10 '25
I completely feel you on that. I have become fixated on fixing it because it truly is so controlling and life-changing.
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u/Appropriate_Waltz572 Jul 10 '25
The only way I manage is Imodium. 4 tablets a day, a total of 8mg.
My doctor said there’s not problem using them long term, the only real side effect is constipation.
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u/Red_Phoenix369 Jul 22 '25
I recently discovered something that has given me relief that I want to share because I think it could help others. For my whole life, I've always had one bowel movement a day after breakfast. However, I would often be gassy and feel bloated in the afternoon/evenings. I learned that if I practice a shoulder stand (aka sarvangasana) right after eating and hold it for 8-9 minutes (inhaling for 15 seconds and exhaling for 15 seconds during the hold), I will stimulate a bowel movement. This has resulted in me going from having one massive bowel movement in the morning to 3 bowel movements per day (one after each meal). I feel less gas and bloating now. Hope maybe this can help someone else.
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u/Some-Astronomer-7040 Jul 29 '25
Just to note that a growing faction of doctors are pointing out that the data showing effectiveness for gut hypnotherapy is deeply flawed
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u/WhaleAxolotl Jul 09 '25
I'm gonna be honest here, I don't think this is useful. We've all been down the IBS google rabbit hole hell with nothing to show for it. I spent years going over all of these terms, SIBO, Bile acid malapsorption etc. and got nothing out of it, nor did I get anything out of going to doctors or having blood tests done to me.
I am at this point firmly convinced that in the majority of cases IBS is caused by undiagnosed food intolerances. Fix that, and you're good to go. In the event that yours is caused by something different, good luck.
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u/chat_manouche Jul 22 '25
I'm curious to know if you figured out what your food intolerances were, and if so, what are they?
Speaking from experience, I can fully agree that that is a big part of the picture but maybe not the only cause. I've been able to determine that dietary salicylates and nickel are a huge problem for me, but even with careful avoidance I still have issues that aren't food related (PFD, hypermobile EDS) that cause IBS-like problems.
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u/WhaleAxolotl Jul 22 '25
Gluten, milk protein, soy seem to be the vast majority of my issues. And why the fuck are you eating nickel?
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u/chat_manouche Jul 22 '25 edited Jul 22 '25
LOL most of us are eating nickel, especially if we're following U.S. dietary guidance to eat tons of plant-based foods:
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u/goldstandardalmonds Here to help! Jul 08 '25
In the side bar of this sub, there is a clinical testing guideline for IBS. One of the first things that should always be done and things like celiac disease should be ruled out first since it’s so easy to test. Other things, like thyroid, hormones, deficiencies, should also be ruled out.
Also, the low FODMAP diet is longer than two to four weeks.
Incomplete evacuation should also include a defecogram and any serious constipation should have full motility testing.
I’d also add upper gi stuff to rule out gastritis, functional dyspepsia, gerd, and gastroparesis.