What causes diarrhea?

Diarrhea occurs when fluid you take in by mouth, or fluid produced in your gastrointestinal tract, is not properly absorbed. Normally, the intestines absorb excessive water from food during the digestive process. When food moves too fast, the intestines cannot absorb water, resulting in loose stools. Diarrhea can also occur when excessive water moves into the bowel from the body.

Conditions that can cause diarrhea include infection, malignancy, inflammation, abdominal trauma, obstruction, and the use of certain medications, such as antibiotics, stool softeners, and laxatives.

Diarrhea can result from a wide variety of gastrointestinal or digestive conditions. The most common cause of diarrhea is a viral infection of the intestines, called viral gastroenteritis (stomach flu or intestinal flu). Inflammatory bowel disease (Crohn’s disease and ulcerative colitis) and irritable bowel syndrome are other common causes of diarrhea.

Gastrointestinal causes of diarrhea

Diarrhea may arise from problems in the digestive tract including:

  • Appendicitis
  • Bacterial or parasitic infection of the gastrointestinal tract
  • Digestive tract surgery
  • Fecal impaction
  • Food intolerances or allergies (lactose, fructose or gluten intolerance)
  • Intestinal obstruction
  • Irritable bowel syndrome
  • Laxative use or abuse
  • Malabsorption syndromes
  • Traveler’s diarrhea
  • Tumors of the small or large intestine (benign or malignant)

Other causes of diarrhea

Diarrhea can also be caused by problems in body systems other than the digestive tract including:

  • Antibiotics
  • Bulimia
  • Cystic fibrosis
  • Hyperthyroidism
  • Low-fat diet
  • Medication side effects (often antibiotics)
  • Nutritional deficiency (zinc)
  • Radiation therapy
  • Tube feeding

Life-threatening conditions associated with diarrhea

In some cases, diarrhea may accompany a serious or life-threatening condition including:

What are the potential complications of diarrhea?

In some cases, diarrhea can lead to serious complications, especially if the diarrhea is severe, continues for a long time, or the underlying disease or condition is untreated or poorly managed. Complications include:

  • Dehydration

  • Diarrhea that contains blood can lead to anemia and shock in some cases

  • Electrolyte imbalance

  • Malnutrition


  1. What I need to know about diarrhea. National Digestive Diseases Information Clearinghouse (NDDIC). http://digestive.niddk.nih.gov/ddiseases/pubs/diarrhea_ez/
  2. Collins RD. Differential Diagnosis in Primary Care, 5th ed. Philadelphia: Lippincott, Williams & Williams, 2012.
  3. Kahan S, Miller R, Smith EG (Eds.). In A Page Signs & Symptoms, 2d ed. Philadelphia: Lippincott, Williams & Williams, 2009.

What is diarrhea?

Diarrhea is the passage of loose, watery stools and/or having bowel movements more frequently than usual. Diarrhea is a common digestive symptom of a wide variety of mild to serious diseases, disorders and conditions.

Diarrhea occurs in all age groups and populations. Depending on the cause, diarrhea can be short term (acute) and disappear relatively quickly, such as when it occur... Read more about diarrheaintroduction


What other symptoms might occur with diarrhea?

Diarrhea may be accompanied by other symptoms, depending on the underlying disease, disorder or condition. Symptoms frequently affect the digestive tract but may also affect other body systems.

Digestive symptoms that may occur along with diarrhea

Diarrhea may accompany other symptoms affecting the digestive tract including:

Medical Reviewer: William C. Lloyd III, MD, FACS Last Annual Review Date: Aug 9, 2013 Copyright: © Copyright 2014 Health Grades, Inc. All rights reserved. May not be reproduced or reprinted without permission from Health Grades, Inc. Use of this information is governed by the HealthGrades User Agreement.

Did You Know?

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Irritable bowel syndrome (IBS) is one of the most common disorders diagnosed by doctors. In fact, it's estimated that as many as 20 percent of adults have symptoms of IBS.