Chronic diarrhea means loose or watery stools that persist for four weeks or longer, and it is a symptom, not a diagnosis: the job is not only to stop it, but to find out what is driving it. The part that surprises most people is this — a colonoscopy can look completely normal while the disease is present, because some of the most common causes of chronic diarrhea are invisible to the naked eye and show up only under a microscope, in a small biopsy taken from lining that looked perfectly healthy. This article walks through how the problem is actually worked up: which tests the guidelines recommend before you are handed the label "IBS", why microscopic colitis and bile acid diarrhea in particular get missed, when the cause is a tablet you take every morning — and when it may be a food category that we ourselves sell.
One note before we start: this is general health education, not a substitute for your doctor. Persistent diarrhea deserves a real medical evaluation, not self-diagnosis.
What counts as chronic diarrhea, and why the definition matters 🩺
The most common mistake is to measure the problem by how many times a day you visit the bathroom. The medical definition does not start with frequency. It starts with consistency and duration. The American Gastroenterological Association (AGA) clinical practice guidelines, published in Gastroenterology in 2019, set their scope precisely: immunocompetent adults with watery diarrhea lasting at least four weeks.
Why does that matter? Because three very different situations get bundled under one word:
- Acute diarrhea: a few days, usually an infection, usually self-limiting.
- Chronic diarrhea: weeks to months — this is the one that deserves a cause.
- More frequent stools with unchanged consistency: which may not be diarrhea at all in the medical sense.
Hence the first rule: "chronic diarrhea" is not an answer, it is a question. It is the title of a file that has not been opened yet. The difference between someone who lives for ten years with "IBS" and someone who recovers in two months is usually that the second person's file actually got opened.
Before the "IBS" label: what do the guidelines actually test for? 🔬
The 2019 AGA guideline exists for exactly this question: what should be tested in the laboratory before chronic diarrhea is called functional, or diarrhea-predominant irritable bowel syndrome? What makes the document genuinely useful is that it does not merely say "test" — it publishes the strength of each recommendation and the quality of the evidence behind it:
- Stool testing for Giardia — a strong recommendation, high-quality evidence.
- Testing for celiac disease with IgA tissue transglutaminase (IgA-tTG) plus a second test to detect celiac disease in the setting of IgA deficiency — a strong recommendation, moderate-quality evidence.
- Fecal calprotectin or fecal lactoferrin to screen for inflammatory bowel disease — a conditional (weak) recommendation, low-quality evidence, with a suggested calprotectin cutoff of 50 μg/g to optimize sensitivity.
- Testing for bile acid diarrhea — a conditional recommendation, low-quality evidence.
- Against using ESR or C-reactive protein in the blood to screen for IBD in this setting — conditional.
- Against routine stool ova and parasites testing (other than Giardia) in people without a travel history — conditional.
Why quote the strength of a recommendation at all?
Because that is the difference between reading a guideline and merely citing one. When an international guideline tells you that only two of six recommendations are strong, it is telling you something valuable: not all tests are equal, and some are offered because they might help, not because the matter is settled. That protects against both extremes — the person who refuses every test and the person who demands all of them. The value is not in the number of tests, but in which ones are supported by evidence and which ones actually change a decision.
This is also not a checklist to run yourself. It is a map for the conversation with your doctor; your age, your symptoms and your family history are what tilt one item over another.
Why a normal colonoscopy is not enough 🔎
This is the spine of the article, and it settles a confusion shared by many people who were told "the scope was excellent, everything is normal" and went home with exactly the same diarrhea.
There is a disease called microscopic colitis. Mayo Clinic explains the name in a single precise sentence: it is a condition "where the large intestine, also called the colon, looks healthy but shows changes when viewed under a microscope." The surface the camera sees is normal; the inflammation lives in the tissue itself.
A review in the Cleveland Clinic Journal of Medicine in 2024 says it even more plainly: the disease "is so named because its diagnosis requires histologic evaluation with mucosal biopsy," and "cross-sectional imaging and endoscopic evaluation are usually normal in the absence of a microscopic evaluation." The review adds useful numbers: a worldwide incidence of about 5 per 100,000 patient-years, with a female predominance; it "occurs at all ages" but is more common in patients older than 60. And the biopsies are taken from the ascending and descending colon — meaning where the sample comes from is part of the diagnosis, not a procedural footnote.
How much is actually caught by biopsy when the scope looks normal?
That question has a pooled answer. A systematic review and meta-analysis published in iGIE in 2023 — "Diagnostic yield of random colon biopsy sampling in patients with chronic diarrhea and normal colonoscopy" — pooled 21 studies and found the biopsy results split roughly as follows: 48% normal, 30% showing a significant histopathological change, and 22% non-significant changes — with microscopic colitis accounting for about 15%.
Read the middle number again: roughly three in ten people whose colonoscopy looked normal had a significant histological change on biopsy. This does not mean everyone with diarrhea needs a biopsy — that decision belongs to your doctor alone — but it does mean that "the scope was normal" is not automatically the end of the road, and that a fair, polite question in the clinic is: "Were biopsies taken? And from where?"
Who is most at risk of microscopic colitis?
Mayo Clinic lists clear risk factors: older age, female sex, coexisting autoimmune conditions (such as celiac disease, rheumatoid arthritis and type 1 diabetes), and specific medications — nonsteroidal anti-inflammatory drugs, proton pump inhibitors, SSRI antidepressants and statins — as well as alcohol and tobacco use. The typical picture is persistent watery diarrhea without blood, possibly with night-time bowel movements, urgency, abdominal discomfort, fatigue and unintended weight loss.
That night-time detail deserves a pause: waking from sleep to pass stool is not a typical feature of an ordinary functional disorder, and it is one of the things to state explicitly to your doctor. Treatment is a physician's decision; the CCJM review notes that first-line therapy "regardless of the subtype, is budesonide 9 mg/day for 8 weeks" — mentioned here for understanding, never for self-treatment. It is a prescription medicine.
Bile acid diarrhea: the cause that lives under someone else's diagnosis 💧
If microscopic colitis is missed because the eye cannot see it, bile acid diarrhea is missed for a completely different reason: it usually already carries another diagnosis — "IBS with diarrhea".
The mechanism is simple and logical. The liver secretes bile acids that help digest fat, and most of them are meant to be reabsorbed at the end of the small intestine. If the load rises or the reabsorption falters, those bile acids spill into the colon, where they stimulate fluid secretion and motility — and the result is urgent, watery diarrhea. An article in the British Journal of General Practice in 2026 describes it as "excess BAs overwhelm the terminal small bowel's absorptive capacity," and notes that the condition "is often misdiagnosed as irritable bowel" syndrome because of "under-recognition and symptom overlap."
So how common is it really? Here is a number worth remembering. A systematic review with meta-analysis (Slattery and colleagues, Alimentary Pharmacology & Therapeutics, 2015) included 6 studies and 908 people meeting accepted criteria for IBS-D, and found a pooled prevalence of bile acid malabsorption of 28.1% (95% CI: 22.6–34%), ranging across studies from 16.9% to 35.3%. The National Institute of Diabetes and Digestive and Kidney Diseases (NIDDK) puts the same finding in plain language: "About a third of people with IBS-D have a more severe form of diarrhea, called bile acid diarrhea."
Known causes include diarrhea that follows gallbladder removal, and disease secondary to Crohn's; but the BJGP article is careful to note that "most cases are idiopathic." If you had your gallbladder removed and then developed chronic diarrhea that was not there before, that is information to say out loud to your doctor — not something to file under "that's just how the body is after surgery."
So why isn't it diagnosed more often? (The honest brake)
Because diagnosing it is not easy everywhere, and it is only fair to say so. NIDDK states outright that "many of the tests for it can be unreliable or inaccessible for many people," and that little is known about its underlying causes. In other words, part of the problem is not a doctor's ignorance but the limits of the available tools. That is precisely why the practical route in many settings is a conversation with a specialist about the possibility itself, rather than a hunt for one particular test.
The 2026 BJGP article also gives a sense of the daily burden: in a quality-of-life study, 80% of people with bile acid diarrhea always had diarrhea, and over half dealt with bloating, pain and the need to stay near a toilet. That alone is reason enough not to live quietly with the symptom.
What if the cause is a tablet you swallow every day? 💊
The list of medicines that can cause diarrhea is neither rare nor mysterious. Mayo Clinic names, among common causes: antibiotics, anti-cancer drugs, and antacids containing magnesium.
The clearest practical example in our region is metformin, one of the most widely prescribed diabetes medicines in the world. The FDA-approved prescribing information for GLUCOPHAGE records, in its clinical trials, diarrhea in 53.2% of people taking the drug versus 11.7% on placebo. A figure that size means the possibility that the medicine is part of the story is not a marginal one.
But the smartest detail in that label is not the percentage — it is the timing. The label notes that "gastrointestinal symptoms, which are common during initiation of metformin therapy, are unlikely to be drug related" when they appear in a patient who has been stabilized on the drug. In other words, a symptom that begins years after you settled onto a medicine should not be waved away as start-up side effects; it deserves evaluation, not reassurance. And the one practical rule here is absolute: never stop a prescribed medicine or change its dose on your own. Take the full list to your doctor and tell them exactly when the diarrhea began.
And now about our own category: sugar alcohols 🍞
It is not typical for a keto, sugar-free bakery to write this paragraph. But honesty outranks selling.
Sweeteners from the sugar alcohol family — sorbitol, mannitol, maltitol and erythritol — are used widely in sugar-free products, including in our category. The U.S. Food and Drug Administration, in its educational material on the Nutrition Facts label, is explicit: foods containing sorbitol or mannitol "must include a warning on their label that states 'excess consumption may have a laxative effect'", adding that sugar alcohols "can also produce abdominal gas, bloating, and diarrhea in some individuals because they are not completely absorbed by the body."
Mayo Clinic, for its part, lists artificial sweeteners — naming sorbitol, erythritol and mannitol — among food components that can cause diarrhea.
What does that mean in practice? Three things we will say plainly:
- If you have chronic diarrhea, products sweetened with sugar alcohols — ours included — are among the first things worth testing by temporarily removing them, and reporting the result to your doctor. We are not exempting ourselves from that list.
- The response is highly individual: an amount that bothers no one may bother you, and the total daily load usually matters more than any single item.
- This is not a reason to abandon healthy eating or to go back to refined sugar — we would never say that — but it is a reason to read the label and know what you are actually eating.
By the same logic, here is something else that may cost us sales: gluten-free bread is not a treatment for chronic diarrhea. And there is a more serious, very common mistake — starting a gluten-free diet before being tested for celiac disease. Mayo Clinic states it clearly: "Until your appointment, continue eating your usual diet. Cutting gluten before you're tested for celiac disease can change the test results." A hasty diet can steal a correct diagnosis from you. (For the distinction between the conditions, see our article on non-celiac gluten sensitivity versus celiac disease.)
What to do before the appointment ✅
- Log two weeks, not an impression. Record daily: how many times, the consistency, the timing (especially at night), what you ate, and every medicine or supplement. Memory softens and exaggerates; paper does not.
- Bring the complete list of your medicines and supplements — including the ones that feel trivial: antacids, painkillers, magnesium-containing supplements.
- Write down the start date. "For a while now" tells a doctor nothing. "It started after my gallbladder surgery in March" or "it started three years into metformin" can change the whole direction.
- Do not delete half your diet at once. Sweeping elimination destroys information and makes diagnosis harder — and, as above, it can invalidate a celiac test. Change one thing at a time, preferably after speaking with your doctor.
- Watch hydration. Prolonged diarrhea loses fluid and salts. Mayo Clinic lists dehydration signs in adults: excessive thirst, dry mouth and skin, passing little urine, weakness, dizziness, fatigue and dark urine.
- Ask the two questions if you have had a colonoscopy: "Were biopsies taken?" and "Has bile acid diarrhea been considered?" A polite question beats ten silent years.
Signs that warrant a doctor — and who should be more careful ⚠️
Mayo Clinic lists, among reasons for adults to see a doctor: diarrhea lasting more than two days, signs of dehydration, severe abdominal or rectal pain, bloody or black stools, and a fever above 102 °F (39 °C). To those, in the chronic setting, add: unintended weight loss, night-time bowel movements that wake you from sleep, and any diarrhea that starts for the first time after age 50 or alongside a family history of bowel disease or colon cancer.
Evaluation should be earlier and more careful in: people with diabetes (because of overlapping medicines and conditions), people with autoimmune disease, older adults (microscopic colitis is more common over 60, and dehydration is more dangerous), pregnant and breastfeeding women, anyone who has had bowel or gallbladder surgery, and anyone on long-term medication. And if your symptoms persist despite "normal tests", that is a reason to keep looking with a specialist — not a reason to give up.
Always consult your doctor before changing any medicine or diet, and never stop a prescribed treatment on your own. What is in this article is education; the clinical decision belongs to your physician.
What the numbers say in Saudi Arabia 🇸🇦
A Saudi cross-sectional survey published in Frontiers in Public Health on 7 August 2026 included 1,553 participants and found that 373 of them (24%) met the Rome IV symptom-based criteria for IBS, with subtypes distributed as 166 (44.5%) diarrhea-predominant, 129 (34.6%) constipation-predominant and 78 (20.9%) mixed.
But the more important part is what the researchers said about their own study — and it is a lesson in reading evidence: "IBS status was based on self-reported Rome IV symptoms rather than clinician-confirmed diagnosis," and among their listed limitations were an "incomplete assessment of alarm symptoms" and the absence of clinical confirmation.
That is precisely the gap this whole article is about: a quarter of the sample carried the symptoms, while the paper itself says the diagnosis was never clinically confirmed and alarm symptoms were not fully assessed. The distance between us and a correct diagnosis is not obscure biology — it is an evaluation that has not happened yet. And the sentence worth saying in the clinic is simple: "My symptoms have lasted more than a month — I'd like to rule out organic causes before we call it IBS."
Where does Bakery 8 stand in all of this? 🥖
Our position is modest and explicit: we treat nothing. Not the bread, not the granola, not the crackers — none of it treats chronic diarrhea, and we will never write otherwise. What we offer is displacement: almond-flour baked goods with no added sugar and no wheat, for people who have chosen a low-carbohydrate pattern or who need to avoid gluten on medical advice.
If you are currently dealing with chronic diarrhea, our professional — not marketing — advice is: keep your diet stable and simple, change one variable at a time, and take what you eat to your doctor. For anyone who wants to explore our range once things settle, our sections are bread, granola and crackers at getbakery8.com. Healthy and delicious — and any promise bigger than that is one we will not make.
To go deeper, we have also written about inflammatory bowel disease and what "remission" really means, about bloating and gas after eating, and about chronic constipation and why more fiber isn't enough.
Frequently asked questions ❓
When does diarrhea become "chronic"?
When watery stools persist for four weeks or more, which is the scope the 2019 AGA guideline set for immunocompetent adults. Anything shorter is classed as acute or persistent and is usually a self-limiting infection. Duration and consistency are the criteria, not frequency alone — which is why writing down exact dates before your appointment is genuinely useful.
My colonoscopy was completely normal. Is that the end of it?
Not necessarily. Microscopic colitis is diagnosed by biopsy, not by appearance, and a 2023 systematic review in iGIE found that about 30% of chronic diarrhea patients with a normal colonoscopy had a significant histological change on biopsy, roughly 15% of them microscopic colitis. Ask your doctor whether biopsies were taken, and from which segments.
What is bile acid diarrhea and why is it missed so often?
It is diarrhea caused by excess bile acids reaching the colon, where they drive fluid secretion and motility. It is missed because it looks exactly like "IBS with diarrhea"; a 2015 meta-analysis found a pooled prevalence of 28.1% within that group, and NIDDK estimates about a third. Raise the possibility with your doctor, especially after gallbladder removal.
Could the cause be a medicine?
Yes, and not rarely. The FDA-approved metformin label records diarrhea in 53.2% of users versus 11.7% on placebo, and Mayo Clinic names antibiotics, anti-cancer drugs and magnesium-containing antacids. But never stop a prescribed medicine yourself — bring your complete medication list to your doctor along with the date your symptoms started.
Can sweeteners in sugar-free products cause diarrhea?
Yes, in some people and at larger amounts. The FDA requires foods containing sorbitol or mannitol to carry the warning "excess consumption may have a laxative effect", and Mayo Clinic lists sorbitol, erythritol and mannitol among causes of diarrhea. The response is individual, and the total daily load usually matters more than any single product.
Should I just try a gluten-free diet and see if I improve?
Not before testing. Mayo Clinic advises continuing your usual diet until your appointment, because cutting gluten beforehand "can change the test results" and makes celiac disease harder to diagnose. Discuss the test with your doctor first, then make the dietary decision based on a reliable result rather than a vague personal experiment.
References
- Smalley W, Falck-Ytter C, Carrasco-Labra A, Wani S, Lytvyn L, Falck-Ytter Y. AGA Clinical Practice Guidelines on the Laboratory Evaluation of Functional Diarrhea and Diarrhea-Predominant Irritable Bowel Syndrome in Adults (IBS-D). Gastroenterology, 2019. doi:10.1053/j.gastro.2019.07.004
- American Gastroenterological Association. Laboratory evaluation of functional diarrhea and diarrhea-predominant irritable bowel syndrome in adults (IBS-D) — clinical guidance summary, gastro.org.
- Mayo Clinic. Diarrhea — Symptoms and causes.
- Mayo Clinic. Microscopic colitis — Symptoms and causes.
- Mayo Clinic. Celiac disease — Diagnosis and treatment.
- National Institute of Diabetes and Digestive and Kidney Diseases (NIDDK). Microscopic Colitis.
- Westbrook KE, Garber A. Microscopic colitis: What is it, and what are the treatment options? Cleveland Clinic Journal of Medicine, 2024;91(4):215–216. doi:10.3949/ccjm.91a.23057
- Loganathan P, et al. Diagnostic yield of random colon biopsy sampling in patients with chronic diarrhea and normal colonoscopy: a systematic review and meta-analysis. iGIE, 2023.
- Slattery SA, Niaz O, Aziz Q, Ford AC, Farmer AD. Systematic review with meta-analysis: the prevalence of bile acid malabsorption in the irritable bowel syndrome with diarrhoea. Alimentary Pharmacology & Therapeutics, 2015;42(1):3–11.
- NIDDK. Identifying distinguishing features of bile acid diarrhea — research update, 2022.
- Thirkettle J, McLaughlin J, Raza M. Bile acid diarrhoea: a clinical conundrum in primary care. British Journal of General Practice, 2026;76(762):45–47. doi:10.3399/BJGP.2025.0613
- U.S. Food and Drug Administration. GLUCOPHAGE (metformin hydrochloride) — Prescribing Information, adverse reactions table.
- U.S. Food and Drug Administration. Interactive Nutrition Facts Label — Sugar Alcohols, October 2021.
- Baig M, et al. Association of irritable bowel syndrome with depression, anxiety, stress, and sociodemographic factors in Saudi Arabia: a cross-sectional survey. Frontiers in Public Health, 7 August 2026. doi:10.3389/fpubh.2026.1866985
Related keywords: chronic diarrhea, causes of persistent diarrhea, microscopic colitis, colon biopsy, normal colonoscopy, bile acid diarrhea, IBS with diarrhea, celiac disease testing, fecal calprotectin, metformin and diarrhea, sugar alcohols, when diarrhea is serious.