What Causes Diarrhea That Lasts More Than Two Weeks?

Diarrhea that lasts more than two weeks has many possible causes, including lingering infections, medicines, food intolerances, celiac disease, inflammatory bowel disease, irritable bowel syndrome, and problems absorbing nutrients. Clinicians combine your history, examination and testing to sort these out. Signs of dehydration, black or bloody stool, severe belly pain, or unplanned weight loss need urgent evaluation. This article covers common causes of long-lasting diarrhea, what a clinician may check, and when to get care.

What counts as diarrhea that lasts more than two weeks?

Diarrhea means loose or watery stools, often three or more times in a day. Most episodes come from a stomach infection and settle within days. When loose stools continue for longer, clinicians start to look beyond a simple infection. MedlinePlus (NIH) describes diarrhea as a symptom with many possible causes, and the cause of a long episode is often different from the cause of a short one.

Clinicians often use the word "persistent" for diarrhea that has gone on for roughly two weeks or more, and "chronic" for longer spans. Exact cutoffs vary between sources, so what matters for you is that a stretch of loose stools with no sign of ending deserves a medical conversation.

Common causes of long-lasting diarrhea

Several factors can contribute, and more than one can be present at the same time. The groups below cover many of the causes clinicians consider.

Infections that linger or return

Some germs can cause symptoms that last longer than the usual stomach bug. Parasites such as Cryptosporidium can cause watery diarrhea that continues for a while, as described on the MedlinePlus cryptosporidiosis page. Contaminated water, including pools, and travel to places with limited sanitation are common exposures. Travelers' diarrhea can sometimes linger, and an expert panel report on prevention and treatment of travelers' diarrhea discusses how it is evaluated and managed.

A bowel infection after antibiotics is another possibility. Antibiotics can disturb the normal gut bacteria, and C. diff infections can follow, sometimes weeks after the medicine. Antibiotics can also cause loose stools without C. diff. Tell your clinician about any recent antibiotic course so they can decide whether testing is appropriate.

Medicines and supplements

Many medicines can loosen stools. Antibiotics are one example. Others include some magnesium-containing antacids and supplements, certain diabetes and blood pressure medicines, and some cancer treatments. Sugar substitutes such as sorbitol, found in sugar-free gum and candy, can also have this effect. Do not stop or change a prescription on your own. Ask the prescriber or pharmacist whether a medicine on your list could be involved.

Food intolerances

Lactose intolerance can cause loose stools, gas and bloating after dairy. It has its own page on this blog, Lactose Intolerance: Why Does Dairy Upset My Stomach?, so the short version is that symptoms after milk products may point to it. Other food-related causes include fructose and sugar alcohols, and large amounts of caffeine or alcohol.

Celiac disease and malabsorption

Celiac disease is an immune reaction to gluten that can damage the lining of the small intestine. It may cause diarrhea, bloating, gas and fatigue, though some people have few digestive symptoms. Clinicians usually check for it with blood tests and sometimes a biopsy. Do not start a gluten-free diet before testing unless your clinician advises it, because that can make results harder to interpret.

More broadly, malabsorption syndromes are conditions in which the intestine does not absorb nutrients well. They can show up as greasy, bulky, foul-smelling stools that may float, along with weight loss. Causes can include celiac disease, pancreas problems and some intestinal infections.

Inflammatory bowel disease

Crohn disease and ulcerative colitis are forms of inflammatory bowel disease (IBD). They can cause ongoing diarrhea, belly pain, urgency, fatigue and sometimes blood in the stool. The related page on this blog, What Does Blood in Your Stool Mean?, covers that symptom in detail. IBD is diagnosed through a combination of history, blood and stool tests, and often a colonoscopy.

Irritable bowel syndrome

Irritable bowel syndrome (IBS) is a common gut disorder that can cause belly pain with diarrhea, constipation, or both. The mechanism is not fully understood. Clinicians generally consider IBS after other conditions have been reasonably excluded, particularly when warning signs such as bleeding or weight loss are present.

Gallbladder, pancreas and bile problems

Problems with how fat is digested can cause loose, oily stools. Gallbladder diseases and a history of gallbladder removal can sometimes be linked with diarrhea, and gallstones can cause pain in the upper right belly. Pancreatic conditions can also reduce fat digestion.

Less common causes

Overactive thyroid, microscopic colitis, and bowel cancer can also cause diarrhea. These are much less common than the everyday causes above, and diarrhea alone does not establish any of them. Colorectal cancer is more often noticed through blood in the stool, a change in bowel habits, anemia or weight loss, which is one reason clinicians take those features seriously. The blog's page on Causes of Unexplained Weight Loss covers that symptom.

Clues that help sort out the cause

Details you can note before your appointment can help your clinician narrow things down:

• Timing: Does it wake you at night? Is it worse after meals or after certain foods?
• Stool appearance: Watery, bloody, black, greasy, or with mucus.
• Other symptoms: Fever, belly pain, weight loss, rashes, joint pain, or mouth sores.
• Exposures: Recent travel, untreated water, daycare contact, or a sick household member.
• Medicines: Antibiotics, supplements, laxatives and anything new.
• Family history: Celiac disease, IBD or bowel cancer in relatives.

What evaluation may involve

Clinicians combine history, examination and testing. Depending on your situation, this may include blood tests (for anemia, inflammation, celiac antibodies and thyroid function), stool tests for infection, C. diff or inflammation, and sometimes imaging. A colonoscopy lets a clinician look at the lining of the colon and take small tissue samples, which can help identify conditions such as IBD or microscopic colitis. Not everyone needs every test.

Staying hydrated and comfortable while you wait for answers

• Drink fluids steadily. Water, broth and oral rehydration solutions can help replace what you lose.
• Eat small, plain meals if that feels better, and note which foods seem to worsen symptoms.
• Limit alcohol, caffeine and sugar-free products containing sugar alcohols.
• Check with a clinician or pharmacist before using anti-diarrheal medicines, especially if you have fever or blood in the stool, because they may not be appropriate in those situations.
• Wash hands well, especially after using the toilet, to avoid spreading an infection.

Diarrhea in infants and young children needs particular care because they can become dehydrated more easily. For a child, follow the product label and ask your pediatrician or pharmacist about any treatment.

Dehydration and other complications

Ongoing diarrhea can lead to dehydration and low levels of salts such as potassium and sodium. Signs can include dark urine or very little urine, dry mouth, dizziness when standing, a racing heartbeat, and unusual weakness or confusion. Long-term diarrhea from malabsorption can also contribute to weight loss and nutrient shortfalls, such as low iron or vitamin levels. Tell your clinician if you feel lightheaded or very tired. The blog's pages on dizziness and fatigue cover those symptoms more broadly.

When to see a clinician

Book a visit if loose stools continue past two weeks, even if you feel otherwise well. Sooner evaluation is reasonable if you have blood in the stool, weight loss you did not intend, fever, waking at night to pass stool, or a recent hospital stay or antibiotic course. The lists below separate emergencies from symptoms that need a prompt appointment.

When to Seek Medical Care