Chronic Diarrhea Causes and Consequences

Chronic Diarrhea
Prasit photo/Getty Images

Frequent diarrhea lasting longer than a few weeks is described as chronic diarrhea, whether it occurs every day or every few days. The causes vary and can be easy to address (by changing medication, for example) or serious health problems that need to be evaluated and treated, such as ulcerative colitis and Crohn's disease. Diarrhea itself can, over time, cause new health problems as well.

Diarrhea is most commonly described as watery stools, but it also means frequent stools (more than three times per day), a substantially larger than normal quantity of stool, or sudden urges to have a bowel movement. If you experience these patterns for several weeks, then you have chronic diarrhea and should be evaluated by a doctor.

How Diarrhea Develops

The colon, also known as the large intestine, is responsible for forming solid waste from the unabsorbed remains of the food you eat. Fluid is also absorbed into the colon as part of that waste, which allows the stool to pass through the colon more smoothly. Muscles in the colon move the stool along to the rectum for passage out of the body.

When something disrupts this process, causing too much water to be absorbed or the solid waste to pass too quickly through the large intestine, diarrhea can result.

Causes of Chronic Diarrhea

Most people have experienced acute, short-term diarrhea, usually as the result of a gastrointestinal infection. Chronic diarrhea, on the other hand, is less common and is typically caused by medical conditions, allergies, medications, or chronic infections.

Medical Conditions

Inflammatory bowel diseases (IBD) such as Crohn's disease and ulcerative colitis are common causes of intermittent, chronic diarrhea. Diarrhea, stomach pain, rectal bleeding, fever, and weight loss may occur for weeks or months on end, often resolving for a period of time before recurring. With these conditions, diarrhea alternates with constipation or with "pencil" (very thin) stools.

Chronic pancreatitis, alcoholic liver disease, cystic fibrosis, and tropical sprue each cause their own collection of unique symptoms, and they all affect the body's ability to absorb nutrients, especially fat, which can result in diarrhea.

Hyperthyroidism often causes diarrhea because excessive thyroid hormones stimulate intestinal movements and impair nutrient absorption. Diabetes can cause nerve damage and may result in a chronic condition called autonomic neuropathy, which impairs the function of internal organs, possibly resulting in chronic diarrhea.

Another condition, described as malabsorption syndrome, occurs when the intestines do not properly absorb nutrients. It can be idiopathic (without a known cause) or it may be a result of excessive antibiotic use, chemotherapy medications, or radiation therapy.

Colon cancer rarely causes any symptoms and is a rare cause of chronic diarrhea accompanied by bloody stools and weight loss.

Food Sensitivities

Several food sensitivities can cause diarrhea, either due to allergic responses or intolerance. For example, if you are lactose intolerant, you cannot absorb the lactose present in dairy products, and this causes a series of events that result in watery stools. Celiac disease is often thought of as a gluten insensitivity because most people experience stomach pain, diarrhea, faitigue and weight loss that improves once gluten containing foods are discontinued.

Some foods cause an inflammatory allergic reaction, resulting in excessive water absorption in the colon and diarrhea. Often, with dietary sensitivity, it is unclear whether the cause of the diarrhea is an allergy or difficulty processing the food.

Sometimes, dietary factors, such as excessive sugar or dairy consumption can cause persistent diarrhea as well, even if you do not have food intolerance.


Medications can induce diarrhea, either as an allergic reaction or as a normal medication side effect. You can develop chronic medication-induced diarrhea even if you have already been taking the medicine without problems for years. Antibiotics can also cause infectious diarrhea because they often destroy the normal bacteria that line your intestines.


Sometimes gastrointestinal infections either don't resolve, have a tendency to recur, or are followed by other infections as a result of antibiotic use (even when used as directed), resulting in lingering infections and diarrhea.

Parasites, which may require specialized medications, are not as easily recognized as other gastrointestinal infections, so they are more likely to linger and cause chronic diarrhea.

Gastric Bypass

Gastric bypass surgery, also often referred to as bariatric surgery or weight loss surgery, often results in substantially diminished absorption of food and liquid in the gastrointestinal system, which results in persistent diarrhea.


If you have chronic diarrhea, you can experience serious health problems, even if your diarrhea is caused by a situation that isn't dangerous, such as a food allergy.

  • Nutrition: Chronic diarrhea can cause you to become dehydrated, as your body loses too much fluid. You can also miss out on vitamins, minerals, proteins, and fats when your diarrhea is associated with a lack of absorption of these vital nutrients. And, chronic diarrhea can also result in weight loss if you aren't absorbing enough carbohydrates and calories from the food you eat.
  • Bleeding and irritation: Chronic diarrhea can cause irritation of the colon or the rectum, potentially resulting in fragile tissue and bleeding.
  • Dehydration: When you lose fluid in the stool, you can become dehydrated. Chronic diarrhea causes mild dehydration, which makes you thirsty. Severe dehydration results in decreased urine volume, dark urine, fatigue, lightheadedness, and low blood pressure. Interestingly, dehydration is more dangerous if you have acute diarrhea, as your body tends to compensate better for dehydration if you have chronic, recurrent diarrhea.

When to See a Doctor

If you have long-term diarrhea, don't put off seeing your doctor. Your doctor may order blood tests or a stool sample to check for blood in the stool or an infection due to bacteria, a virus, or a parasite. You may need a colonoscopy or flexible sigmoidoscopy, which may identify IBD or early signs of colon cancer. Even if it turns out that you have colon cancer, it is highly curable with long-term survival rates well over 90 percent when detected early.

Signs that you should see your doctor include:

  • Your diarrhea has lasted for more than two weeks (either intermittently or the entire time).
  • You see blood in or on your stool.
  • You have persistent abdominal cramps or severe pain.
  • You're vomiting a lot.
  • You experience alternating constipation and diarrhea.
  • You notice you're losing weight even though you haven't been trying to.

A Word From Verywell

Persistent diarrhea is hard to ignore. Most of the time, the reason behind it is not life-threatening, but the cause and the potential health complications need to be addressed so that you can maintain your energy, nutrition, and a healthy weight.

Was this page helpful?
Article Sources