Patient Education Patient Information


Patient Education


What is Diarrhea?

Diarrhea is when bowel movements are loose, watery, and sometimes more frequent. Diarrhea is one of the most commonly reported illnesses but is not usually serious.  Most people have diarrhea for a few days and can be treated with over-the-counter options. Many people will experience diarrhea a couple times each year.


Gastroenterology Consultants of San Antonio - Diarrhea

If diarrhea lasts for weeks or longer, it could indicate a more serious illness like inflammatory bowel disease or infection.  Diarrhea with blood present may also be a sign of serious illness. People with long-lasting or bloody diarrhea should be seen by a medical professional. Schedule an appointment if you have these symptoms. 

Those who are very young, old, or sick may need medical attention with diarrhea.  Because it can cause dehydration, these populations may not be able to replace all the water and salts necessary for the body to function.

Diarrhea Symptoms

Symptoms of diarrhea include:
  • Watery, thin, or loose stools
  • Abdominal pain
  • Abdominal cramping or bloating
  • Fever
  • Nausea or vomiting
  • Bloody or black stools
  • Urgency to have a bowel movement
  • Weight Loss or dehydration
See a doctor if you:
  • Have diarrhea that lasts more than two days
  • Have bloody or black stools
  • Have severe rectal or abdominal pain
  • Have a fever above 102F
  • Become dehydrated
Signs of dehydration can include:
  • Urine that is darker in color
  • Urinating less
  • Increased heart rate
  • Headaches
  • Irritability
  • Confusion

What Causes Diarrhea?

The most common cause is a virus in the bowel (viral gastroenteritis).  This is sometimes called “intestinal flu” and can last for 1-2 days.


Viral hepatitis, cytomegalovirus, and Norwalk virus can all cause diarrhea.  In children, rotavirus is a common cause of acute diarrhea.


Ingesting food or water that is contaminated can transfer parasites to your body.  Cryptosporidium and Giardia lamblia are two parasites that can cause diarrhea. Drinking untreated water, such as from a stream in the woods, is often associated with contracting parasites.


Contaminated food and water can carry bacteria into the body.  Common bacterial illnesses that can cause diarrhea include salmonella, Escherichia coli (E. coli), Shigella, and Campylobacter.

Traveler’s Diarrhea

Diarrhea caused by parasites and bacteria when traveling abroad is often called traveler’s diarrhea.  You are at increased risk of developing traveler’s diarrhea when you visit someplace where the sanitary conditions or climate are different from what your body is used to.  Symptoms typically go away after one to two days and treatment isn’t necessary.


Some medications can cause diarrhea, including antibiotics.  Antibiotics destroy bacteria – both good and bad – which can disrupt the balance of natural bacteria in the bowels. Cancer treatment drugs and antacids with magnesium may also cause diarrhea.


Those who are lactose intolerant may experience diarrhea after consuming milk or dairy products.  Lactose is the sugar found in milk and dairy products that some people have trouble digesting.


Fruits and honey contain a natural sugar called fructose that can cause diarrhea in some people.  Fructose is also used as a sweetener in beverages.

Artificial Sweeteners

Artificial sweeteners found in sugar-free products and chewing gum may cause some people to have diarrhea.  The ingredient names are sorbitol and mannitol.


Abdominal surgery or surgery to remove the gallbladder may cause diarrhea.

Digestive Illnesses

Crohn’s disease, celiac disease, ulcerative colitis, and irritable bowel syndrome can cause diarrhea.


To diagnose diarrhea, doctors will review your medical history and perform a physical exam first.  This will include questions about recent diet changes, travel, and any medications you may be taking.  Other tests for diarrhea may include:

Stool Test

A stool test can help determine if diarrhea is caused by a parasite or bacterium.

Blood Test

Blood tests can help determine the cause of diarrhea. Bloodwork can help identify concerns with infections and anemia, kidney function, electrolytes, and albumen (nutrition).


If the cause of diarrhea cannot be determined, your doctor may recommend a colonoscopy or sigmoidoscopy.  These procedures allow the doctor to view the lining of the colon using a thin, flexible tube with a small camera at the end.

How to Treat Diarrhea

Most cases of mild diarrhea do not require treatment.  Home remedies and over-the-counter medications can help.  If your symptoms persist longer than two days, your doctor may recommend alternative treatments or medications.

Treating Diarrhea Without Medication

Diarrhea usually clears up without medication. A supportive diet can treat your symptoms and help you get the nutrients and hydration you need. Here’s what to eat:

  1. Drink more fluids

Diarrhea can cause dehydration very quickly, so it’s critical that you try to take in fluids as much as possible. Sip fluids throughout the day and/or increase the total intake of water to two to three liters if possible. Clear broths, fruit juice (without pulp), rehydration drinks, sports drinks, and tea with honey are helpful. These liquids replace the water and salt your body needs to function properly. Avoid alcohol and caffeine.

  1. Gradually add low-fiber foods

As your stools become more solid, slowly increase your intake of low fiber foods. These may include bananas, smooth peanut butter, chicken (no skin), lean ground beef, fish, cottage cheese, yogurt, rice, potatoes, noodles, and applesauce.

  1. Avoid dairy, high-fat, high-fiber and spicy foods

Fried or greasy foods, raw fruits and vegetables, spicy foods, and whole-grain breads and cereals are harder to digest.

What is the BRAT Diet?

The BRAT diet is a simple way to remember how to stop diarrhea with foods you may already have at home. It refers to four foods that are both bland and binding. They’re unlikely to irritate your digestive system and may help make stool firm.

Brat stands for:

  • Bananas
  • Rice
  • Apples
  • Toast

Those are the foods easiest to remember, but other foods can be eaten on the BRAT diet, including:

  • Applesauce
  • Cooked cereals
  • Soda crackers

Treating Diarrhea With Medication


Antibiotics can help treat diarrhea if the cause is parasites or bacteria.  Antibiotics will not help if your diarrhea is caused by a virus. A stool test can help determine if antibiotics are appropriate.

Adjust Medications

Sometimes a medication, such as an antibiotic, causes diarrhea. In this case, your doctor may switch to another medication or lower your dose.

Over-the-counter medications

Anti-diarrheal medications available over-the-counter may help reduce symptoms. Loperamide (Imodium A-D) and bismuth subsalicylate (Pepto-Bismol) is widely available.

If the infection is caused by a parasite or bacterium, these medications could worsen the condition.  Your body will try to remove what’s causing diarrhea and these medications may prevent that from happening.

Your doctor will likely recommend diagnosing the cause of your diarrhea if it is severe or lasts longer than two days.


Probiotics are beneficial microbes that are typically found in your gut, where they help maintain your immune system. There are estimated to be trillions of microbes in your gut. The entire population of microbes in your gut is called the gut microbiome. A healthy microbiome is essential to your digestive health. Diarrhea can destroy the balance of your microbiome, and it can also be a result of an unbalanced microbiome.

Antibiotics can also affect the gut microbiome. If you have diarrhea that needs to be treated with antibiotics, it may affect more microbes than just the ones causing diarrhea. Taking probiotics may help.

Probiotics can help repopulate your gut microbes. They can be taken as a supplement and are also found in fermented foods, like:

  • Kimchi
  • Kombucha
  • Miso
  • Pickles
  • Sauerkraut
  • Some cheeses
  • Yogurt

Diarrhea Prevention

Preventing diarrhea caused by a virus:
  • Wash hands frequently with soap – especially before and after meals, food preparation, using the bathroom, changing diapers, sneezing or blowing your nose. Lathering the soap for 20 seconds is the most effective.
  • Hand Sanitizer – If hand washing isn’t an option, using a hand sanitizer with alcohol can help.  The hand sanitizer should contain at least 60% alcohol.
  • Vaccination – Vaccines are available for some root causes.  Infants can be vaccinated against rotavirus, the most common cause of viral diarrhea in young children.
Preventing traveler’s diarrhea

When you travel to underdeveloped countries, or where sanitation standards are lower, take the following precautions to avoid traveler diarrhea:

  • Eat hot, completely cooked foods. Avoid raw fruits and vegetables unless you peel them yourself.  Avoid undercooked or raw dairy foods and meats.
  • Avoid tap water and ice cubes – Instead, drink bottled water.  Beer, wine, and soda from the original container should be safe.  Hot beverages, such as coffee and tea, are generally safe.
  • Hygiene – use bottled water to brush your teeth and keep your mouth closed when showering.
  • Antibiotics – Talk to your doctor about taking antibiotics leading up to and during your trip.  This may reduce the risk of developing diarrhea while traveling.

What if You Get Diarrhea After Eating?

Diarrhea is often caused by bacteria or a virus, but sometimes the cause is something you ate or drank. Certain foods may trigger diarrhea in some people. Common culprits include:

  • Alcohol
  • Caffeine
  • Coffee
  • Cruciferous vegetables
  • Dairy products
  • Fast food
  • Fructose
  • Garlic
  • Onions
  • Spicy foods
  • Sugar substitutes, including artificial sweeteners and sugar alcohols

If you seem to be having random bouts of diarrhea, it can help to keep a food diary listing everything you eat. You may notice a pattern of diarrhea after eating certain foods and know to avoid them in the future.

What is Chronic Diarrhea?

Most people occasionally have acute diarrhea (short-term) without complications. However, when diarrhea becomes a long-term problem, it may indicate an underlying health problem. It can also cause severe dehydration, which can be life-threatening.

Chronic diarrhea is when diarrhea occurs three or more times in 24 hours and continues for four or more weeks. It may also come with abdominal cramping, bloating, and nausea.

It can be caused by:

A blood test or stool sample may help your doctor identify the cause and determine a treatment. Sometimes, the cause is never found. Treatment for chronic diarrhea may include lifestyle and diet changes, medications, probiotics, or psyllium.

Diarrhea FAQ

Is diarrhoea the same as diarrhea?
Yes, diarrhoea is the British spelling of diarrhea.

What causes watery diarrhea?
Watery diarrhea is often caused by bacteria, a parasite, or a virus.

What causes green diarrhea?
Eating green, purple, or iron-rich foods can cause green stool. It can also indicate a viral infection or result from food moving through your digestive system too quickly.

What causes yellow diarrhea?
Bright yellow diarrhea can indicate an infection caused by giardiasis, an intestinal parasite. A giardiasis infection also causes symptoms like abdominal pain, fever, gas, headache, loss of appetite, nausea, and vomiting, and a swollen abdomen. Yellow can also indicate a problem with the gallbladder or liver.

What causes black diarrhea?
Black diarrhea can be caused by ingesting black licorice, dark-colored foods, iron supplements, or Pepto-Bismol®. It can also indicate that you have bleeding in your digestive tract. If you have black stool for no apparent reason, call your doctor immediately.

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