There are many reasons why you might develop diarrhea after drinking water, such as sulfate contamination, IBS, overhydration, or malabsorption of a substance like lactose.

Diarrhea is defined as passing loose and watery stool more than three times a day. Common causes include:

Drinking water is an uncommon trigger. There are several reasons why water might cause diarrhea, including:

  • the water contains a substance that stimulates your bowels
  • stretching of your stomach is triggering your gastrocolic reflex
  • you’re drinking too much water
  • your intestines can’t absorb the water

Read on to learn about some of the reasons water may trigger diarrhea.

Here are some potential reasons why you may get diarrhea after drinking water.

High sulfate levels

High sulfate levels in your drinking water can cause diarrhea and dehydration, especially if your body isn’t used to it. Children and adults usually build a tolerance to sulfate levels after a few days.

The U.S. Environmental Protection Agency (EPA) has set the maximum allowable sulfate level at 250 milligrams per liter. Amounts higher than this tend to have a bitter taste.

Osmotic diarrhea

Osmotic diarrhea occurs when components of your food stay in your bowel without getting absorbed and draw water into your intestines. Excess water in your bowel can lead to watery stools.

Potential causes include:

Water intoxication (water poisoning)

Water intoxication happens when you drink large amounts of water in a short period of time, which can dilute electrolytes in your blood and cause life threatening symptoms, such as:

Water intoxication is frequently associated with water or other liquid drinking contests. Other causes include:

  • drinking excessive water after exercise without replenishing electrolytes
  • a condition called psychogenic polydipsia, which is compulsive water-drinking
  • over-replenishing water if you have a condition causing high antidiuretic hormone levels

Irritable bowel syndrome

Your gastrocolic reflex helps control the mobility of food through your GI tract. When your stomach stretches, this reflex increases muscular contractions to help pass food through.

A problem with the gastrocolic reflex is a suspected cause of irritable bowel syndrome (IBS). It’s thought that some people with IBS may have an overactive gastrocolic reflex that causes stool to pass quickly through the GI tract shortly after eating.

In theory, drinking a lot of water could stretch your stomach and provoke the gastrocolic reflex.

Dumping syndrome

Dumping syndrome is when food passes through your stomach too quickly, usually within 30 minutes of a meal. It can cause symptoms like:

Problems with the gastrocolic reflex are thought to potentially play a role in the development of dumping syndrome when the cause is unknown. Drinking large amounts of liquids can potentially trigger this reflex.

Traveler’s diarrhea

Traveler’s diarrhea occurs when you’re traveling to areas where the food or water is contaminated with:

  • bacteria
  • viruses
  • parasites

E. coli is the most common cause of traveler’s diarrhea, making up about 30% of cases. E. coli infection can lead to osmotic diarrhea.


Dysentery is a GI infection caused by bacteria or amoebae that can cause osmotic diarrhea. Potential bacterial causes include:

Amebic dysentery is rare in the United States and usually develops in people who have recently visited tropical regions.

Medication use

Some medications can cause osmotic diarrhea, such as:

  • magnesium-containing laxatives
  • antacids
  • the laxative lactulose

Food poisoning

Food poisoning develops when you consume food containing harmful bacteria. Some types of bacteria that cause food poisoning, such as E. coli, can cause osmotic diarrhea.

Other causes

Other potential causes of diarrhea after drinking water include:

  • conditions that cause carbohydrate malabsorption, such as:
  • Crohn’s disease
  • taking too many laxatives
  • a cause unrelated to the water you’re working

Potential causes of diarrhea on an empty stomach include:

  • infections
  • IBS
  • dumping syndrome
  • water intoxication

Here are some potential treatment options for diarrhea.

Home remedies

Home remedies include:

CauseHome remedy
Sulfate in drinking water• avoiding water with high levels of sulfate and drinking bottled water
Overhydration• reducing fluid intake
• consuming electrolytes
IBS• eating smaller meals
• drinking water or fluids after your meal
Dumping syndrome• eating smaller meals more frequently
• avoiding liquids for 30 minutes after your meal
• avoiding dairy and simple sugars
Infections• eating bland foods like:
• bananas
• rice
• applesauce
• toast
• avoiding alcohol
• eating foods high in probiotics
Medication side effects• stopping or changing the dose of certain medications

Learn more about home remedies for diarrhea.

Medical treatments

Medical treatments include:

• sodium replenishment through an IV (intravenous) infusion
• stopping medications causing the problem
IBSanti-diarrheal medications
Dumping syndrome• medications like tolbutamide (Orinase) and propranolol (Hemangeol, Inderal)
• surgery
Infections• bismuth subsalicylate (Pepto-Bismol)
• antibiotics
• antiparasitic medications

It’s a good idea to seek medical attention if:

  • your diarrhea lasts more than 7 days
  • your diarrhea is particularly severe
  • you notice blood in your stool
  • you have stool that’s black or dark
  • you’re losing weight
  • you have a severe or continuous stomach ache
  • you’re unable to keep fluids down

Developing diarrhea after drinking water can be a sign that your water contains sulfate or is contaminated with another substance. Usually, you develop a tolerance to sulfate over a few days, and it’s safe to continue drinking it, as long as levels fall within EPA standards.

If your diarrhea doesn’t go away after a few days, it’s a good idea to see your doctor.