Diarrhea: Causes, Treatment and When to See a Doctor

What counts as diarrhea

Diarrhea is about consistency and frequency. Normal stool ranges from once every 3 days to three times a day. Diarrhea is loose or watery stool (types 6 and 7 on the Bristol Stool Chart) three or more times a day.

Thinner stools vs diarrhea vs normal stools

Passing frequent, small, formed stools is not diarrhea. Leakage of liquid stool around hard, impacted stool, common in older adults and children, can look like diarrhea but is actually severe constipation.

Common causes of acute diarrhea

• Viral gastroenteritis: norovirus is the leading cause in adults, with sudden vomiting and watery diarrhea lasting 1 to 3 days. Rotavirus mainly affects unvaccinated young children.
• Food poisoning: bacteria such as Salmonella, Campylobacter, E. coli and Shigella, or toxins from Staphylococcus or Bacillus cereus. Toxin-related illness starts within 1 to 6 hours of eating. Bacterial infection usually starts 1 to 3 days later and may cause fever and bloody stools.
• Traveler's diarrhea: usually from bacteria in contaminated food or water.
• Parasites: Giardia (from untreated water) and Cryptosporidium (from swimming pools) cause watery diarrhea, bloating and gas that can last weeks.
• Medicines: antibiotics, magnesium-containing antacids, metformin, some chemotherapy, and laxatives.
• C. difficile: a gut infection after antibiotics, causing frequent, foul-smelling watery diarrhea and sometimes severe colitis.
• Too much caffeine, alcohol, artificial sweeteners (sorbitol, xylitol) or fructose.

Causes of chronic diarrhea

Diarrhea lasting more than 4 weeks is called chronic diarrhea. Common causes:

• Irritable bowel syndrome: cramps relieved by bowel movements, alternating stool habits, bloating, no blood or weight loss.
• Lactose intolerance: gas, bloating and diarrhea after dairy.
• Celiac disease: an immune reaction to gluten, causing diarrhea, bloating, weight loss, anemia or tiredness.
• Inflammatory bowel disease: Crohn's disease and ulcerative colitis cause bloody or urgent diarrhea, belly pain and weight loss.
• Microscopic colitis: watery diarrhea in older adults, often linked to NSAIDs or some other medicines.
• Bile acid diarrhea, especially after gallbladder removal.
• Overactive thyroid, diabetes-related nerve damage, and pancreatic insufficiency.
• Colorectal cancer: rarely, a lasting change toward looser stools, especially over 50, with bleeding or weight loss.

Symptoms that come with diarrhea and what they suggest

• Vomiting first, then diarrhea: viral gastroenteritis or toxin food poisoning.
• Fever and bloody stools: invasive bacterial infection or inflammatory bowel disease. See bloody diarrhea.
• Greasy, pale, floating stools: malabsorption from celiac disease or pancreatic problems.
• Diarrhea at night that wakes you: suggests an organic cause rather than IBS.
• Weight loss: suggests celiac disease, IBD, an overactive thyroid or cancer.

Signs of dehydration

In adults: thirst, dark urine, passing little urine, dry mouth, tiredness, dizziness when standing, headache. In babies and young children: fewer wet diapers, no tears when crying, a dry mouth, sunken eyes, a sunken soft spot on the head, and being unusually sleepy or irritable. See dehydration.

How to treat diarrhea at home

Replace fluids

• Oral rehydration solution (ORS): the best option for moderate diarrhea and for children, older adults and anyone at risk of dehydration. It contains the right balance of salts and sugar to help the gut absorb water. Buy it at a pharmacy.
• For mild diarrhea in healthy adults, water, diluted juice, broths and soups are usually enough.
• Sip small amounts often if you feel sick, for example a few mouthfuls every 5 to 10 minutes.
• Avoid sports drinks, sodas and undiluted fruit juice as the main fluid for children, because the high sugar can worsen diarrhea.
• Babies: keep breastfeeding or formula feeding, and offer ORS between feeds if advised.

Eat normally as soon as you can

There is no need to starve. Eat small meals of plain foods as your appetite returns, such as rice, toast, bananas, potatoes, crackers, soup, eggs, yogurt and cooked vegetables. A strict BRAT diet (bananas, rice, applesauce, toast) alone is no longer recommended for long, because it lacks protein and fat. Avoid fatty, spicy or very sugary foods, alcohol and lots of caffeine until you recover.

Medicines

• Loperamide can reduce the number of bowel movements in adults with watery diarrhea. Follow the label dose. Do not use it with bloody diarrhea or high fever, and do not give it to young children unless a doctor advises it.
• Bismuth subsalicylate can ease diarrhea and nausea in adults. It contains a salicylate, so do not give it to children or teenagers, and it can turn the tongue and stool black.
• Antibiotics are not needed for most diarrhea. They are used for specific infections, severe traveler's diarrhea, C. difficile and some parasites.
• Probiotics may slightly shorten diarrhea in some cases, but evidence is mixed.

Avoid spreading it

Wash hands with soap and water after using the toilet and before preparing food. Alcohol hand gel does not kill norovirus well. Stay off work or school until 48 hours after the last episode of diarrhea or vomiting, and do not prepare food for others during that time.

How doctors find the cause

Most short bouts of diarrhea need no tests. For bloody, severe, persistent or travel-related diarrhea, or after antibiotics, a doctor may arrange stool tests for bacteria, parasites and C. difficile toxin, and blood tests for dehydration, kidney function and inflammation. For chronic diarrhea, tests can include celiac blood tests, fecal calprotectin (a marker of gut inflammation), thyroid tests, and colonoscopy with biopsies.

Preventing diarrhea

• Wash hands thoroughly, especially after the toilet and before eating.
• Cook meat and eggs thoroughly and refrigerate leftovers promptly.
• When traveling in areas with unsafe water, drink bottled or treated water and eat food that is cooked and served hot.
• Make sure babies get the rotavirus vaccine.
• Take antibiotics only when needed.

Frequently asked questions

How long does diarrhea usually last?

Most acute diarrhea from viruses or food poisoning lasts 1 to 4 days, and nearly all resolves within 2 weeks. Diarrhea lasting 2 to 4 weeks is called persistent, and over 4 weeks is chronic. See a doctor if diarrhea lasts more than 7 days in an adult or 5 to 7 days in a child.

How do I stop diarrhea fast?

Focus on fluids first, ideally an oral rehydration solution. Eat small, plain meals. Healthy adults can take loperamide at the label dose for watery diarrhea, but not with blood in the stool or a high fever. Most diarrhea stops on its own as the infection clears.

What should I eat when I have diarrhea?

Eat small amounts of plain foods such as rice, toast, bananas, potatoes, crackers, soup, yogurt, eggs and cooked vegetables. Avoid greasy, spicy or very sugary foods, alcohol and lots of caffeine. Keep drinking fluids. Return to a normal diet as soon as you feel able.

When should I worry about diarrhea?

Get medical help for signs of dehydration, blood or black stools, severe belly pain, fever above 39 °C (102 °F), diarrhea after antibiotics or a hospital stay, or diarrhea lasting more than a week. Babies, older adults, pregnant people and those with long-term illness should be checked sooner.

Are thin stools the same as diarrhea?

No. Thin or narrow stools describe shape, while diarrhea describes loose or watery consistency and increased frequency. Narrow stools are usually caused by straining, constipation or IBS. New, persistently pencil-thin stools, especially with bleeding or weight loss, should be checked to rule out a narrowing in the colon.