Diarrhea that lasts a few days is usually caused by a viral infection, something you ate, or a medication side effect, and it resolves on its own. If it’s been going on longer than two weeks, the list of possible causes shifts toward food intolerances, chronic gut conditions, or ongoing medication effects. How long you’ve been dealing with it is the single most useful clue for narrowing down the cause.
How Long It’s Lasted Matters Most
Diarrhea falls into three categories based on duration, and each one points toward different causes. Acute diarrhea lasts less than a week and is the most common type. Persistent diarrhea stretches beyond two weeks but resolves before four. Chronic diarrhea lasts four weeks or longer and almost always needs medical evaluation.
Most people searching this question are somewhere in the acute-to-persistent range, wondering whether what they’re experiencing is normal or a sign of something bigger. A single bout of loose stools after a questionable meal is rarely concerning. But if you’ve noticed a pattern over days or weeks, it’s worth thinking through the most likely explanations.
Viral and Bacterial Infections
The most common cause of short-term diarrhea is a viral gut infection, sometimes called stomach flu. Rotavirus and norovirus are the usual culprits. These infections typically bring on watery diarrhea, nausea, and sometimes vomiting that peaks within one to three days and clears up within a week without treatment.
Bacterial infections from contaminated food or water can hit harder. Salmonella, Campylobacter, and certain strains of E. coli cause diarrhea that may include cramping, fever, and occasionally blood in the stool. Food poisoning from bacteria tends to come on suddenly, often within hours of eating the contaminated food, and usually runs its course in a few days. If you recently traveled internationally, parasitic infections like Giardia are also worth considering, as these can cause diarrhea that lingers for weeks if untreated.
Foods and Sweeteners That Pull Water Into Your Gut
If your diarrhea seems to follow meals or specific foods, your diet is a strong suspect. Lactose intolerance is one of the most common triggers. If your body doesn’t produce enough of the enzyme that breaks down milk sugar, dairy products can cause bloating, gas, and diarrhea within a few hours of eating them.
Sugar alcohols, the sweeteners found in “sugar-free” gum, candy, protein bars, and some diet drinks, are another frequent cause that people overlook. Ingredients like sorbitol, xylitol, and erythritol are poorly absorbed in the small intestine. When they reach the colon, they draw water in by increasing osmotic pressure, essentially flooding the bowel with fluid. Whether this happens depends partly on your gut bacteria. People whose gut microbes can break down these sweeteners tolerate them better, while others get diarrhea from even small amounts.
Fructose, the sugar naturally found in fruit and added to many processed foods as high-fructose corn syrup, can cause the same osmotic effect in people who absorb it poorly. Coffee, alcohol, and spicy foods are also well-known triggers, though they work through different mechanisms, mainly by speeding up the movement of food through your intestines.
Medications You Might Not Suspect
Nearly any medication can cause diarrhea, but some are far more likely to do it than others. Antibiotics are the most obvious offender. They disrupt the balance of bacteria in your gut, which can lead to loose stools during or even after finishing a course. In some cases, antibiotics allow a bacterium called C. difficile to overgrow, causing severe, persistent diarrhea that needs its own treatment.
Beyond antibiotics, several everyday medications commonly cause diarrhea:
- Metformin, widely prescribed for type 2 diabetes, is one of the most frequent culprits
- Heartburn and acid reflux medications like omeprazole (Prilosec), lansoprazole (Prevacid), and famotidine (Pepcid)
- NSAIDs like ibuprofen and naproxen, used for pain and inflammation
- Magnesium-containing antacids, which draw water into the intestines the same way sugar alcohols do
- Herbal teas and supplements containing senna or other natural laxative compounds
If your diarrhea started around the same time you began a new medication or supplement, that connection is worth exploring with your prescriber.
Chronic Conditions That Cause Ongoing Symptoms
When diarrhea lasts four weeks or longer, or keeps coming back in cycles, a chronic condition becomes more likely. The three most common are irritable bowel syndrome (IBS), inflammatory bowel disease (IBD), and celiac disease. They share some overlapping symptoms but differ in important ways.
IBS is the most common of the three. It causes recurring abdominal pain along with changes in bowel habits, including diarrhea, constipation, or both. The key distinction is that IBS does not cause inflammation or physical damage to your digestive tract. It’s a disorder of how the gut functions, not a structural problem. Symptoms often worsen with stress, certain foods, or hormonal changes.
IBD, which includes Crohn’s disease and ulcerative colitis, is an autoimmune condition that causes actual inflammation and damage to the digestive tract. Unlike IBS, IBD can cause symptoms beyond the gut, including joint pain, skin problems, and fatigue. It can also prevent your body from absorbing nutrients properly. Bloody stool, significant weight loss, and fevers are more characteristic of IBD than IBS.
Celiac disease is an immune reaction triggered specifically by gluten, a protein in wheat, barley, and rye. It damages the lining of the small intestine over time, leading to diarrhea, bloating, weight loss, and nutrient deficiencies. Unlike IBD, which can affect any part of the digestive system, celiac disease targets the small intestine and has a clear dietary trigger. A blood test can screen for it, and the condition is managed by eliminating gluten entirely.
How Doctors Figure Out the Cause
If your diarrhea has lasted more than two weeks, a doctor will typically start with blood tests looking for signs of inflammation, infection, anemia, or celiac disease. Stool tests can check for hidden blood, markers of intestinal inflammation, and specific infections like C. difficile. A breath test can identify whether bacteria are overgrowing in your small intestine, a condition that causes bloating and diarrhea.
If those initial tests don’t point to a clear answer, imaging or a colonoscopy with tissue samples may be the next step. This is especially likely if you have red flag symptoms like blood in your stool, unexplained weight loss, or a family history of IBD or colon cancer.
What to Eat While You’re Dealing With It
The old advice to stick strictly to bananas, rice, applesauce, and toast (the BRAT diet) isn’t wrong, but it’s more restrictive than necessary. Those foods are easy on the stomach, but there’s no research showing they work better than other bland options. Brothy soups, oatmeal, boiled potatoes, crackers, and unsweetened dry cereals are equally gentle and provide more variety.
After a day or two, you can start adding foods with more nutritional value: cooked carrots, sweet potatoes without skin, avocado, skinless chicken or turkey, fish, and eggs. These are still easy to digest but give your body the protein and nutrients it needs to recover. The bigger priority is staying hydrated, since diarrhea pulls a significant amount of water and electrolytes out of your body. Water, broth, and oral rehydration solutions all help.
Signs That Need Prompt Attention
Most diarrhea is uncomfortable but not dangerous. However, certain symptoms signal that something more serious may be going on. Seek medical attention if you experience bloody or black stools, a fever above 102°F (39°C), severe abdominal or rectal pain, or signs of dehydration like excessive thirst, dark urine, dizziness, or very little urination. Diarrhea that hasn’t improved at all after two days also warrants a call to your doctor.
For children, the timeline is shorter. A child whose diarrhea hasn’t improved within 24 hours, who has no wet diaper for three or more hours, or who seems unusually sleepy or unresponsive needs medical evaluation. Severe diarrhea, defined as more than 10 bowel movements a day or fluid losses that outpace what you can drink, can cause dangerous dehydration regardless of age.