What else gets called IBS?
Why this happens so often
IBS is diagnosed on symptom pattern using the Rome criteria, together with the absence of alarm features. That is a legitimate way to diagnose it. The gap opens between the criteria and the appointment: a ten-minute consultation, a recognizable set of symptoms, no obvious red flags, then the label is applied without the short list of exclusions ever being worked through.
The result is a large group of people who probably do have IBS, sitting alongside a smaller group who have something specific, treatable and missed. You cannot tell which group you are in from the inside, which is exactly why the exclusions exist.
What commonly turns out to be something else
Roughly in order of how often it is missed rather than how serious it is.
- Celiac disease. The most important one, because the test is cheap and the testing gets botched constantly. See the FAQ below on why cutting gluten before the blood test ruins it.
- Bile acid malabsorption. Genuinely common in people labeled IBS-D and genuinely under-tested. It responds to a specific treatment, so getting the label right changes what happens next.
- Endometriosis. Frequently mistaken for IBS, with a diagnostic delay measured in years. Worth raising specifically if symptoms track your cycle or come with pelvic pain.
- Inflammatory bowel disease. Crohn's and ulcerative colitis. Fecal calprotectin is the usual first separator. We cover the distinction in IBS versus IBD.
- Microscopic colitis. Easy to miss because the colon looks normal during a colonoscopy. It is found on biopsy, so it depends on whether biopsies were taken.
- Infection. Giardia and H. pylori both produce a convincing imitation of IBS. Both are treatable once identified.
- SIBO. Contested, over-diagnosed commercially, but real. Our SIBO explainer covers what the testing can and cannot show.
- Carbohydrate enzyme deficiencies. Lactase deficiency is the familiar one. Sucrase-isomaltase deficiency is rarer and much less often considered.
- Pancreatic exocrine insufficiency. Produces fatty, hard-to-flush stools and is checked with a stool test.
- Thyroid disease. Both directions change bowel habit. It is one blood test.
Two others belong here for a different reason. Ovarian and bowel cancer are rare causes of these symptoms, which is why this is not a page about cancer. They are also the reason the red-flag list exists and is not negotiable. Persistent bloating that does not come and go, particularly with appetite change or pelvic pain, needs assessment rather than a diet.
Being useful in the appointment
"I think I was misdiagnosed" tends to go badly. Asking which exclusions were done goes well, because it is a specific and answerable question.
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Ask which exclusions were done
And when. Often the answer is more than you think. Occasionally it is nothing. Either way you now know where you stand rather than guessing.
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Say what has changed since
A diagnosis given five years ago described five-year-old symptoms. New or different symptoms are a reason to look again. That framing is much easier to act on than doubting the original call.
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Bring a record, not a recollection
Frequency, timing, stool form, what changed and when. This is the difference between "it is been bad lately" and something clinically legible. What a food diary should show your doctor covers what to bring.
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Do not change your diet first
Particularly not gluten. Several tests need you to still be eating the thing being tested for. Preparing for a gastroenterology appointment has the rest.
The honest caveat
Communities like this one select hard for the people whose label was wrong. Someone whose IBS diagnosis was correct, whose symptoms improved and who moved on does not write the post. That makes misdiagnosis feel far more common than it is, which is worth holding onto, because the alternative failure mode is real: years of tests, escalating anxiety and no answer, in someone who had IBS the whole time.
A confirmed IBS diagnosis with the exclusions properly done is a good outcome. It is a condition with things that genuinely help. The point of this page is to make sure the diagnosis you are working from is one you can trust, then get on with treating it.
Sources
- Rome Foundation, Rome IV diagnostic criteria for irritable bowel syndrome.
- NICE guideline CG61, Irritable bowel syndrome in adults: diagnosis and management, on initial investigation and referral criteria.
- British Society of Gastroenterology guidelines on the management of irritable bowel syndrome, covering celiac serology and fecal calprotectin in initial assessment.
- Endometriosis UK and NICE guidance on diagnostic delay and on symptoms that warrant gynecological assessment.
Frequently asked
Does this mean my IBS diagnosis is probably wrong?
Probably not. IBS is common, it is a positive diagnosis under the Rome criteria rather than a shrug, so most people given the label do have it. The useful question is narrower: were the specific exclusions actually done in your case? Many people were diagnosed on symptoms alone without a celiac blood test or a stool calprotectin. Both are quick to check.
Which tests should have been done before diagnosing IBS?
At minimum, celiac serology while you were still eating gluten, a full blood count, ferritin and inflammatory markers. Fecal calprotectin is the standard way to separate IBS from inflammatory bowel disease and is a stool sample rather than a procedure. Which further tests are appropriate depends on your symptoms, which is a conversation with your doctor rather than a checklist to demand.
Why does celiac testing keep going wrong?
Because the blood test looks for your immune response to gluten, so it needs gluten in your diet to detect anything. People commonly cut gluten first, feel better, then get tested and come back negative. That result means very little. If you have already stopped, say so before being tested rather than after, because the reintroduction needed to test properly is unpleasant and worth planning.
I am a woman with severe cyclical bloating. What should I raise?
Symptoms that track your menstrual cycle, pelvic or lower back pain, pain during sex, or bloating severe enough that people ask whether you are pregnant are all worth raising specifically, because endometriosis is frequently mistaken for IBS and the average delay to diagnosis is measured in years. Persistent bloating that does not come and go also needs assessment in its own right.
When should I stop experimenting and see someone?
Immediately, if you have bleeding, unintended weight loss, a change in bowel habit persisting over about six weeks in someone over fifty, anemia, a mass, waking at night with pain or diarrhea, or a family history of bowel cancer or inflammatory bowel disease. Those are not things to test with a food diary. They are reasons to be examined.