Recurring diarrhea usually points to something your body is reacting to on a regular basis, whether that’s a food, a medication, or an underlying digestive condition. If loose stools have been coming and going for more than four weeks, it’s considered chronic diarrhea, and there’s almost always an identifiable cause. The good news is that most of those causes are treatable once you figure out what’s driving them.
Your Diet May Be the Simplest Explanation
Certain sugars pull extra water into your intestines, which loosens your stool. One of the biggest culprits is fructose, found naturally in fruits like apples, pears, peaches, and cherries, and added to sodas, juice drinks, and applesauce. Most people who consume more than 40 to 80 grams of fructose per day will develop diarrhea, and that threshold is easier to hit than you’d think if you’re drinking fruit juice or sweetened beverages throughout the day.
Sugar-free products are another common trigger. The sugar alcohols used in sugar-free gum, candy, and some medications (sorbitol, mannitol, and xylitol) are poorly absorbed in the gut and have a laxative effect. Lactose, the sugar in dairy, works the same way in people who don’t produce enough of the enzyme to break it down. All of these belong to a group of poorly digested sugars called FODMAPs, and they share the same basic mechanism: they sit in your intestines undigested, draw in water, and get fermented by gut bacteria, producing gas, bloating, and loose stools.
If you suspect a dietary trigger, a two-to-three-week elimination trial, cutting out one category at a time, is the most practical way to identify it. Keeping a food diary alongside your symptoms can reveal patterns you wouldn’t notice otherwise.
Medications That Cause Recurring Loose Stools
Drug-induced diarrhea is surprisingly common and often overlooked. Antibiotics are the most well-known offenders, but plenty of everyday medications can do it too. Heartburn drugs like omeprazole and famotidine, NSAIDs like ibuprofen and naproxen, magnesium-containing antacids, and metformin (used for diabetes) all frequently cause diarrhea as a side effect. If your loose stools started around the same time you began a new medication, or if you’re taking one of these drugs daily, the connection is worth exploring with your prescriber. In many cases, switching to a different formulation or adjusting the dose resolves the problem entirely.
IBS With Diarrhea
Irritable bowel syndrome is one of the most common reasons people deal with ongoing diarrhea, and it’s a functional disorder, meaning your gut looks completely normal on imaging and scopes but doesn’t work the way it should. The nerve endings lining your bowel are unusually sensitive, and the muscles that move food through your intestines contract in irregular patterns. Researchers believe the core problem is a disrupted communication loop between the brain and the gut, which is why stress and anxiety so reliably make symptoms worse.
IBS typically shows up as chronic abdominal pain or cramping that improves after a bowel movement, along with bloating, gas, mucus in the stool, and diarrhea that may alternate with constipation. To meet the diagnostic criteria, these symptoms need to be present for at least 12 weeks over the past year, though they don’t have to be consecutive. Importantly, IBS does not cause bleeding, fever, weight loss, or anemia. If you’re experiencing any of those, something else is going on.
Bile Acid Malabsorption
Your liver produces bile acids to help digest fat. Normally, your small intestine reabsorbs most of them before they reach the colon. When that recycling system fails, excess bile acids flood the large intestine and trigger watery diarrhea, often urgently and especially after meals. This condition, bile acid malabsorption, is far more common than most people realize. Studies show it’s present in roughly one-third of patients diagnosed with IBS with diarrhea and up to 50 percent of people with unexplained chronic diarrhea. It’s frequently misdiagnosed as IBS because the symptoms overlap so heavily, but it responds to a completely different treatment.
Food Intolerances and Celiac Disease
Celiac disease deserves its own mention because it’s both common and commonly missed. In one study of 200 patients with chronic, unexplained diarrhea, 15.5 percent turned out to have celiac disease. In celiac, gluten (a protein in wheat, barley, and rye) triggers an immune reaction that damages the lining of the small intestine, impairing your ability to absorb nutrients. Beyond diarrhea, it can cause fatigue, iron deficiency, unintentional weight loss, and skin rashes. A blood test can screen for it, and a biopsy of the small intestine confirms the diagnosis. The critical detail: you need to still be eating gluten for the tests to be accurate. If you’ve already cut it out and your symptoms improved, mention that to your doctor before testing.
Infections That Linger
Most stomach bugs resolve in a few days, but certain parasites are built for the long haul. Giardia, a waterborne parasite picked up from contaminated water, unwashed produce, or person-to-person contact, typically causes symptoms lasting two to six weeks, and sometimes longer in people with weakened immune systems. The diarrhea tends to be greasy and foul-smelling, often accompanied by cramping, nausea, and significant gas. If your diarrhea started after travel, camping, or exposure to untreated water, a stool test for parasites is worth requesting specifically, since standard stool cultures don’t always look for them.
Inflammatory Bowel Disease
Inflammatory bowel disease, which includes Crohn’s disease and ulcerative colitis, is a different category entirely from IBS. While IBS is a problem with how the gut functions, IBD involves real, visible inflammation that damages intestinal tissue and can be seen on imaging and colonoscopy. It carries an increased risk of colon cancer over time and sometimes requires surgery. The key distinguishing symptoms are bleeding, anemia, unintentional weight loss, and fever. These are not features of IBS, and their presence should prompt further evaluation.
Microscopic Colitis
This condition is worth knowing about because it’s easy to miss. The colon looks entirely normal during a standard colonoscopy. The inflammation is only visible under a microscope, which means it’s only diagnosed when a doctor takes tissue samples during the procedure. Microscopic colitis is most common in women and people over 50, though recent research has also linked it to smoking in younger adults, particularly those between 16 and 44. The hallmark symptom is persistent, watery, non-bloody diarrhea. If you’ve had a colonoscopy that came back “clean” but you’re still dealing with daily loose stools, it’s reasonable to ask whether biopsies were taken.
Signs That Need Prompt Attention
Certain symptoms alongside diarrhea signal something more serious. Bloody or black stools, a fever above 101°F, severe abdominal or rectal pain, signs of dehydration (dark urine, dizziness, dry mouth), or unintentional weight loss all warrant a doctor’s visit sooner rather than later. Diarrhea that persists beyond two days without any improvement also deserves medical attention, especially if it’s getting worse or if you can’t keep fluids down.