What Causes Chronic Diarrhea?

Chronic diarrhea is usually caused by a condition that affects digestion, absorption, intestinal movement, or the gut microbiome. Common causes include irritable bowel syndrome (IBS), celiac disease, inflammatory bowel disease (IBD), lactose or fructose intolerance, certain infections, medication side effects, small intestinal bacterial overgrowth (SIBO), pancreatic problems, and complications after abdominal surgery. Chronic diarrhea generally means loose or watery stools lasting at least four weeks.

What Is Chronic Diarrhea?

Diarrhea means having loose or watery stools three or more times a day, or having bowel movements that are noticeably more frequent than normal for you. While short-term diarrhea is common and often resolves within days, chronic diarrhea continues for at least four weeks and may occur continuously or come and go. According to the National Institute of Diabetes and Digestive and Kidney Diseases (NIDDK), chronic diarrhea can affect up to about 5% of people in the United States.

Chronic diarrhea is not a disease by itself. It is a symptom that can have many different causes. Sometimes the reason is relatively straightforward, such as lactose intolerance or a medication side effect. In other cases, persistent diarrhea can be associated with conditions that require medical evaluation, including celiac disease, Crohn’s disease, ulcerative colitis, microscopic colitis, or an ongoing infection.

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What Causes Chronic Diarrhea?

There is no single answer to the question, “What causes chronic diarrhea?” Doctors generally consider several categories of possible causes, including infections, food intolerances, digestive disorders, medications, previous surgery, and disorders involving communication between the brain and digestive system.

Irritable Bowel Syndrome

Irritable bowel syndrome, commonly called IBS, is one possible cause of long-lasting diarrhea. IBS can cause recurring abdominal pain along with changes in bowel habits. Some people primarily experience diarrhea, sometimes referred to as IBS-D.

IBS is considered a disorder of gut-brain interaction. This means symptoms can be related to how the digestive tract and nervous system communicate and function together. Stress can worsen symptoms for some people, although chronic diarrhea should not automatically be attributed to stress without considering other potential causes.

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Celiac Disease

Celiac disease is an immune reaction to gluten that can damage the small intestine and interfere with nutrient absorption. Chronic diarrhea may occur along with bloating, abdominal discomfort, fatigue, weight changes, or other digestive symptoms.

Because untreated celiac disease can affect nutrient absorption, persistent diarrhea accompanied by unexplained weight loss or nutritional problems deserves medical evaluation. A healthcare professional can determine whether testing for celiac disease is appropriate.

Inflammatory Bowel Disease

Inflammatory bowel disease includes Crohn’s disease and ulcerative colitis. These conditions involve chronic inflammation in the digestive tract and can cause persistent diarrhea.

Depending on the condition and affected area, people may also experience abdominal pain, urgency, fatigue, fever, weight loss, or blood in the stool. Blood or black, tarry stool should not be ignored because it can indicate bleeding and requires prompt medical attention.

Lactose Intolerance and Other Food Intolerances

Food intolerance is another common explanation for recurring diarrhea. Lactose intolerance occurs when the body has difficulty digesting lactose, the natural sugar found in milk and many dairy products. Eating lactose-containing foods may lead to diarrhea, gas, bloating, and abdominal discomfort.

Other carbohydrates can also cause symptoms in susceptible individuals. Fructose, sucrose, and sugar alcohols such as sorbitol, mannitol, and xylitol can contribute to diarrhea in some people. Sugar alcohols are commonly found in certain sugar-free gums, candies, and other products.

A food diary can sometimes help identify patterns between meals and symptoms. However, eliminating large numbers of foods without professional guidance may make it harder to maintain adequate nutrition.

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Infections

Although infections commonly cause short-term diarrhea, certain infections can lead to persistent or chronic symptoms. Parasites such as Giardia can cause prolonged diarrhea, particularly after exposure to contaminated water or food. Some bacterial infections can also result in ongoing digestive symptoms.

In some cases, diarrhea can continue after the original infection has resolved because the digestive system temporarily has difficulty processing certain foods. Antibiotic-associated diarrhea is another important consideration, particularly when symptoms develop during or after antibiotic treatment.

Medication Side Effects

Some medications can cause diarrhea, particularly when taken regularly. Antibiotics are a well-known example because they can alter the normal balance of bacteria in the intestine and may increase the risk of Clostridioides difficile, commonly called C. diff, infection.

Other medicines and supplements may also contribute to diarrhea. Some heartburn medications, magnesium-containing products, certain cancer treatments, and other medications can have diarrhea as a side effect. If chronic diarrhea began after starting or changing a medication, tell your healthcare professional rather than stopping a prescribed medicine on your own.

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Small Intestinal Bacterial Overgrowth

Small intestinal bacterial overgrowth, or SIBO, occurs when there is an abnormal increase in bacteria in the small intestine. It may be associated with bloating, abdominal discomfort, gas, and diarrhea.

SIBO can have different underlying causes, so simply treating diarrhea without identifying why symptoms are occurring may not address the underlying problem. A healthcare professional can determine whether SIBO or another digestive condition should be investigated.

Pancreatic and Digestive Problems

The pancreas plays an important role in digestion. Certain pancreatic disorders can interfere with the digestion and absorption of nutrients and may contribute to chronic diarrhea.

Other digestive conditions affecting the small intestine, colon, or bile flow can also cause ongoing changes in bowel movements. The appearance of stool, associated symptoms, weight changes, and medical history can provide important clues when a doctor is evaluating the cause.

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Microscopic Colitis

Microscopic colitis is an inflammatory condition of the colon that can cause chronic, watery diarrhea. Unlike some other inflammatory bowel conditions, the colon may look relatively normal during a standard visual examination, with microscopic examination of tissue samples being important for diagnosis.

People with unexplained, persistent watery diarrhea may therefore need a more detailed evaluation if initial testing does not reveal the cause.

Previous Abdominal Surgery

Some people develop chronic diarrhea after surgery involving the digestive system. Operations involving the gallbladder, small intestine, large intestine, pancreas, liver, stomach, or esophagus can sometimes affect digestion or the movement of food through the gastrointestinal tract.

For example, some people develop dumping syndrome after certain stomach or esophageal surgeries, and diarrhea can be one of its symptoms. Your surgical history is therefore an important part of diagnosing chronic diarrhea.

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What Symptoms Can Occur With Chronic Diarrhea?

Chronic diarrhea can occur by itself, but other symptoms may provide clues about the underlying cause. These can include abdominal cramping, abdominal pain, bloating, nausea, urgency, accidental bowel leakage, fatigue, and unexplained weight loss.

The appearance of stool can also be relevant. Watery diarrhea may point toward different causes than greasy or unusually bulky stools associated with problems absorbing nutrients. Blood, pus, or black and tarry stool is more concerning and warrants prompt medical evaluation.

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How Is Chronic Diarrhea Diagnosed?

Diagnosing chronic diarrhea usually begins with a detailed medical history. A doctor may ask how long the diarrhea has been present, how frequently bowel movements occur, what the stool looks like, what foods and drinks you consume, what medications you take, whether you have recently traveled, and whether you have a personal or family history of digestive disorders.

A physical examination may also be performed. Depending on your symptoms and medical history, your healthcare professional may order stool tests to look for blood, bacteria, parasites, or other signs of disease. Blood tests may help identify inflammation, nutritional problems, dehydration, or other possible causes. Additional testing may be recommended when the initial evaluation does not identify the reason for persistent diarrhea.

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Can Diet Help With Chronic Diarrhea?

Dietary changes can help some people, but the appropriate diet depends on the underlying cause. If a particular food intolerance is responsible, reducing or avoiding the triggering food may improve symptoms. For example, someone with lactose intolerance may need to reduce lactose-containing foods.

Keeping a food and symptom journal can help identify patterns. Record what you eat and drink, when symptoms occur, and whether particular foods consistently make diarrhea worse. NIDDK recommends discussing dietary changes with a healthcare professional, particularly when chronic diarrhea is involved, because nutritional needs still need to be met.

It is generally not a good idea to follow an extremely restrictive diet or eliminate many food groups without guidance. Chronic diarrhea itself can contribute to dehydration and malabsorption, making adequate fluid and nutrient intake especially important.

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When Should You See a Doctor About Chronic Diarrhea?

Because chronic diarrhea lasts at least four weeks, persistent or recurring symptoms should be discussed with a healthcare professional rather than simply treated as an occasional stomach problem. Finding the cause is particularly important when diarrhea is accompanied by weight loss, significant abdominal pain, blood in the stool, fever, or signs of nutrient deficiencies.

Adults should seek medical attention promptly for severe abdominal or rectal pain, bloody or black stools, significant dehydration, or other serious symptoms. NIDDK also advises adults to talk with a doctor right away when diarrhea is accompanied by high fever, six or more loose stools in a day, frequent vomiting, or symptoms of dehydration.

Signs of dehydration can include excessive thirst, dry mouth or skin, very little urination, dark urine, weakness, dizziness, or lightheadedness. Severe dehydration can become dangerous if not treated.

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How Is Chronic Diarrhea Treated?

Treatment depends on the underlying cause. There is no single treatment that works for every person with chronic diarrhea. A doctor may recommend dietary changes for a food intolerance, specific treatment for an infection, medication changes when an existing medicine is contributing to symptoms, or targeted therapy for an inflammatory or digestive disorder.

For some people with IBS, treatment may involve dietary adjustments, stress management, and medications designed to control particular symptoms. People with inflammatory bowel disease or celiac disease require condition-specific medical management.

The goal should not simply be to stop diarrhea temporarily. Identifying and treating the underlying cause can help reduce recurring symptoms and protect against complications such as dehydration and malabsorption.

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Frequently Asked Questions About Chronic Diarrhea

1. How long does diarrhea have to last to be considered chronic?

Chronic diarrhea generally means loose or watery stools lasting at least four weeks. Symptoms can be continuous or may come and go during that period.

2. What is the most common cause of chronic diarrhea?

There is no single cause that is considered responsible for every case. Common possibilities include IBS, food intolerances, celiac disease, inflammatory bowel disease, infections, medication side effects, SIBO, and other digestive disorders. A medical evaluation is often necessary to determine the specific cause.

3. Can stress cause chronic diarrhea?

Stress can worsen digestive symptoms in some people, particularly those with disorders of gut-brain interaction such as IBS. However, persistent diarrhea should not automatically be blamed on stress. Other medical causes should be considered when symptoms continue.

4. Can lactose intolerance cause chronic diarrhea?

Yes. People who have difficulty digesting lactose can develop diarrhea, bloating, and abdominal discomfort after consuming lactose-containing foods or beverages.

5. Can antibiotics cause chronic diarrhea?

Antibiotics can cause diarrhea by changing the balance of bacteria in the intestine. They can also increase the risk of C. difficile infection, which can cause significant diarrhea. Persistent diarrhea during or after antibiotic treatment should be discussed with a healthcare professional.

6. Is chronic diarrhea a sign of colon cancer?

Colon cancer can cause changes in bowel habits, including diarrhea, but chronic diarrhea has many other, more common potential causes. Persistent diarrhea accompanied by blood in the stool, unexplained weight loss, anemia, significant pain, or other concerning changes should be medically evaluated.

7. Can dehydration happen with chronic diarrhea?

Yes. Repeated loose stools can cause the body to lose significant amounts of water and electrolytes. Excessive thirst, dry mouth, dark urine, very little urination, weakness, dizziness, and lightheadedness can be signs of dehydration.

8. What tests are used to find the cause of chronic diarrhea?

Depending on symptoms and medical history, doctors may use blood tests and stool tests. Stool testing can look for blood, bacteria, parasites, or other abnormalities. Additional investigations may be recommended when necessary.

9. Should I change my diet if I have chronic diarrhea?

Possibly, but the right dietary changes depend on the cause. A food and symptom journal can help identify possible triggers. If you have chronic diarrhea, discuss significant dietary restrictions with a healthcare professional so you continue getting adequate nutrition.

10. When should I seek urgent medical care for diarrhea?

Seek prompt medical attention if diarrhea is accompanied by severe abdominal or rectal pain, bloody or black stools, significant dehydration, frequent vomiting, high fever, or other severe symptoms. Adults with diarrhea and six or more loose stools per day should also contact a healthcare professional promptly.

Final Takeaway

So, what causes chronic diarrhea? The answer can range from relatively common problems such as IBS, lactose intolerance, medication side effects, and food sensitivities to conditions such as celiac disease, inflammatory bowel disease, persistent infections, microscopic colitis, SIBO, and other digestive disorders. Chronic diarrhea is defined as diarrhea lasting at least four weeks, so ongoing symptoms deserve more attention than an occasional episode of loose stool.

If diarrhea keeps returning or does not go away, the most useful next step is identifying the underlying cause rather than relying only on temporary symptom relief. A healthcare professional can evaluate your symptoms, medical history, diet, medications, and appropriate test results to determine the best course of treatment. This article is for educational purposes and does not replace individualized medical advice.

Medical Disclaimer: This article is intended for general health education and is not a substitute for individualized medical advice, diagnosis, or treatment. If you have persistent, severe, or unexplained constipation, or any warning symptoms such as bleeding, severe abdominal pain, vomiting, fever, inability to pass gas, or unexplained weight loss, contact a qualified healthcare professional promptly.

Medically reviewed information sourced from trusted health organizations.

Reviewed by: Dzarro Editorial Team
Fact-checked using trusted medical and scientific sources.