What Causes Diarrhea?

Diarrhea has several different causes. Traditionally, practitioners will first determine the type of diarrhea (acute or chronic) in order to find the possible cause.

The Bristol Stool Scale is often used to differentiate between constipation and diarrhea. This helps medical professionals determine which treatment is appropriate to manage symptoms.1

Acute Diarrhea

This type of diarrhea refers to watery stools that usually lasts for only few days, and often arises due to infection. This is very common. People get it after eating improperly prepared food, often at a restaurant. It can also happen on holiday, otherwise deemed ‘travellers diarrhea’. In these cases, formal diagnosis may not be necessary, since its self-limiting and there is no obvious bleeding.

Chronic Diarrhea

This type of diarrhea lasts for more than 3 weeks. It may require formal diagnosis to identify the exact cause and determine an appropriate treatment.

The causes of chronic diarrhea are rather wide and varied. Various tests can help identify the potential cause. Doctors must consider, among other things, the following:

  • Food intolerances
  • Reactions to medications
  • Intestinal diseases such as Crohn’s Disease and Ulcerative Colitis
  • Malabsorption
  • Certain cancers
  • Over-active thyroid
  • Alcohol abuse

In a consultation, your doctor may ask you to avoid certain foods such as lactose, carbohydrates or wheat, in order to check your body’s response.

The doctor may also recommend special tests, such as a sigmoidoscopy or colonoscopy where a thin, flexible tube is passed into the bowel. The enables your doctor to check for inflammation and any other intestinal abnormalities.


  1. Wilkins T, Pepitone C, Alex B, Schade RR. Diagnosis and management of IBS in adults. Am Fam Physician. 2012;86:419-426

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