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Secretory vs. Osmotic Diarrhea: Types of Diarrhea and Their Symptoms

Medically reviewed by Regina Victoria Boyles, MD · Pediatrics

Written by Ruby Anne Hornillos · Updated Sep 20, 2023

Secretory vs. Osmotic Diarrhea: Types of Diarrhea and Their Symptoms

Diarrhea, coupled with digestive upset, is never fun. Aside from the obvious discomfort it brings, diarrhea can also trigger other unwanted conditions like dehydration and electrolyte imbalance. Most of the time, diarrhea and its symptoms only last for a few days. But what happens if this condition goes on for weeks? What about its different types? Read on to learn more about secretory vs osmotic diarrhea.

What is Diarrhea?

secretory vs osmotic diarrhea

Your bowel movement is reflective of your overall health. How often you go to the bathroom, the consistency of your stool, and even the appearance of your stool can offer a closer look at your gut health and hint at underlying medical conditions. When you feel sick, a sudden change in appetite and bowel movement is often the first notable change in your body.

Diarrhea happens when stool becomes watery and loose. A person suffering from diarrhea also notices that they have to go to the bathroom more often than they’re used to. It’s also nearly impossible to ignore the urge to go to the bathroom when you have diarrhea, and the discomfort is often accompanied by abdominal pain and cramps.

A healthy bowel movement, as described in the Bristol Stool Chart, is smooth and soft. Passing a healthy stool should not be a painful ordeal. On the other hand, a person with diarrhea will have a mushy stool. They will also feel the need to empty their bowels numerous times a day and still feel unsatisfied.

What Causes Diarrhea?

Causes of diarrhea can vary from person to person and can depend on the type. Secretory vs osmotic diarrhea can be attributed to different reasons. In general, diarrhea can result from:

  • Bacteria in contaminated food and water.
  • Viral infections, such as the rotavirus, norovirus, viral hepatitis, etc.
  • Medications such as antibiotics (clindamycin or erythromycins) 
  • Food intolerances and allergies
  • Artificial sweeteners commonly found in sugar-free food like mannitol, sorbitol, and erythritol 
  • Digestive disorders
  • Radiation therapy

Secretory vs Osmotic Diarrhea: What Are The Symptoms of Diarrhea?

Typically, there are three (3) basic categories of diarrhea, namely: inflammatory, watery, and fatty diarrhea. Watery diarrhea can be further divided into osmotic, secretory, and functional diarrhea. Despite the various types, symptoms are usually the same, even for secretory vs osmotic diarrhea.

Signs that you may be suffering from a case of diarrhea include:

  • Feeling bloated despite already going to the bathroom several times.
  • Feeling nauseous and vomiting.
  • Fecal incontinence, or suddenly being unable to control your bowel movement.
  • Presence of blood or mucus in your stool.

Watery Diarrhea: Osmotic Diarrhea

The main difference between secretory vs osmotic diarrhea lies in its causes. Osmotic diarrhea typically occurs when an unabsorbed substance or solutes from food prevents normal water absorption in the intestines. This excess water results in the watery stools that characterize diarrhea.

Another critical difference between secretory vs osmotic diarrhea is how it can be resolved. Osmotic diarrhea usually resolves itself when a person stops eating the food containing the trigger for their diarrhea. Substances and food that can trigger osmotic diarrhea include:

  • Laxatives containing lactulose and citrate of magnesia.
  • Milk and other dairy products which lactose.
  • Excessive amounts of vitamin C or sorbitol.

Watery Diarrhea: Secretory Diarrhea

Secretory diarrhea occurs when too much water is secreted in the small intestinal lumen for the body to absorb. This type of diarrhea is also common among those infected with Vibrio cholerae, the organism responsible for the disease cholera. 

Another significant difference between secretory vs osmotic diarrhea is that secretory diarrhea occurs when electrolytes, too ,are secreted into the intestine. Furthermore, symptoms caused by this kind of diarrhea won’t be eliminated through fasting alone. Some possible causes of secretory diarrhea include:

  • Vasoactive Intestinal Peptide Tumors (VIPoma) are known to cause watery and loose stools.
  • Medication for asthma and cardiovascular conditions.
  • Antidepressants.
  • Ingestion of arsenic and pesticides. 
  • When To See A Doctor

    Typically, symptoms of diarrhea are resolved without medical intervention. However, it may be best to seek the advice of a medical professional if your stool remains watery and loose after two days, accompanied by a fever and severe pain. Although secretory vs. osmotic diarrhea symptoms are similar, the treatment will vary depending on the underlying conditions that need to be addressed. 

    Key Takeaway

    Diarrhea is the onset of watery and loose bowel movement, accompanied by abdominal pain and nausea. The various types of diarrhea are often dependent on what causes digestive upset resulting in a change in bowel movement. Osmotic diarrhea is characterized by loose stools caused by substances that the stomach is unable to absorb. Meanwhile, secretory diarrhea usually results from the secretion of water and electrolytes in the intestines. 

    Learn more about diarrhea prevention and management here.


    Hello Health Group does not provide medical advice, diagnosis or treatment.

    Medically reviewed by

    Regina Victoria Boyles, MD


    Written by Ruby Anne Hornillos · Updated Sep 20, 2023

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