Short answer

Diarrhea means three or more loose or watery stools in a day. Most cases come from a stomach infection, food or medicine and clear within a few days. Staying hydrated matters. See a doctor if it lasts more than two days, or if you have blood, black stool, a high fever, severe pain or signs of dehydration.

What causes loose or watery stool?

Loose or watery stool is most often caused by viral stomach infections or food poisoning, but medicines, food intolerances, IBS and inflammatory bowel disease can also cause it.

  • Viral infections (stomach flu) and bacterial food poisoning. The most common causes of short-term diarrhea.
  • Travelers' diarrhea from contaminated food or water.
  • Medicines. Antibiotics, metformin, magnesium antacids and some others. Antibiotics can also allow the bacterium C. difficile to overgrow, which can cause severe, watery diarrhea.
  • Food intolerance. Lactose, fructose, and sugar alcohols such as sorbitol in sugar-free products.
  • Irritable bowel syndrome. Recurring loose stool with cramps and bloating.
  • Inflammatory bowel disease and celiac disease. Longer-lasting diarrhea, sometimes with blood, weight loss or tiredness.
  • Stress, caffeine and alcohol can also loosen stool.

How long is too long for diarrhea?

Diarrhea that lasts up to about two weeks is called acute. Diarrhea lasting four weeks or more is chronic and needs a proper medical workup. In adults, see a doctor if diarrhea continues beyond two days. For babies, young children and older adults, contact a clinician sooner, because they dehydrate faster.

What does the color of diarrhea mean?

Diarrhea is often green or yellow because food moves through quickly, but black or bloody diarrhea can mean bleeding and needs medical advice.

  • Yellow diarrhea is common with infection or food triggers. If it is greasy and foul-smelling, see yellow stool.
  • Green diarrhea usually means food moved through quickly. See green poop.
  • Black diarrhea can come from iron or bismuth, but if it is sticky and tar-like it can mean bleeding. See black stool.
  • Bloody diarrhea needs medical advice. See blood in stool.

General points people are often given

  • Staying hydrated is the main concern. A pharmacist can tell you about oral rehydration solutions and whether they suit you.
  • Some people find bland food easier when they feel able to eat.
  • Alcohol, caffeine, very fatty food and sugar-free products with sugar alcohols can make loose stool worse for some people.
  • Good handwashing helps stop infections spreading.
  • Babies, young children, older adults, pregnant people and anyone with a long-term condition should get advice early.

When should you see a doctor about diarrhea?

See a doctor if diarrhea lasts more than two days. Blood, black stool, a high fever, severe pain or signs of dehydration need care right away.

Call a doctor

  • Diarrhea for more than two days
  • Diarrhea that started during or after antibiotics
  • Diarrhea with weight loss, or one that keeps coming back

Get care now

  • Blood in stool, or black tarry stool
  • A fever above 102 °F (39 °C), or severe belly pain
  • Signs of dehydration: very dry mouth, little or no urine, dizziness, fast heartbeat
  • A baby or young child with watery diarrhea, fewer wet diapers or unusual sleepiness

Warning signs to know

These are signs that published medical guidance says need prompt or urgent care. The list is not complete, and ticking boxes cannot tell you whether you are ill. If you are worried, contact a clinician whatever you tick.

Warning signs

Questions people ask

What is the difference between loose stool and diarrhea?

Diarrhea is usually defined as three or more loose or watery stools in a day. A single soft stool is not diarrhea.

Why is my stool watery?

Usually an infection, food or medicine. Food moves through the gut too quickly for water to be absorbed. It often clears in a few days.

What foods help stop diarrhea?

There is no food that reliably stops diarrhea. Staying hydrated matters most. Ask a doctor or pharmacist for advice that fits your situation.

Can stress cause loose stools?

Yes. Stress and anxiety can speed up the gut and cause loose stools, especially in people with IBS.

When is diarrhea an emergency?

When there is blood or black stool, a high fever, severe pain, or signs of dehydration, and in babies and young children with watery stool and fewer wet diapers.

Sources

Important. This page is general information only. It is not medical advice and is not a substitute for advice, diagnosis or treatment from a qualified healthcare professional. StoolColor is not written or reviewed by a doctor, and using this site does not create a doctor-patient relationship. Always ask a doctor or other qualified clinician about any symptom or medical question, and never ignore or delay professional advice because of something you read here.

If you think you may have a medical emergency, call 911 or your local emergency number right away. Information may be incomplete or out of date. Brand names are trademarks of their owners. StoolColor is not affiliated with those owners, or with the organizations whose publications it cites. See our medical disclaimer and terms of use.

Keep reading