Why Do I Have Diarrhea?

Diarrhea is one of the most common digestive problems and affects people of all ages. It is usually caused by a short-term infection or something you have eaten, but it can also result from medications, food intolerances, chronic digestive diseases, or underlying medical conditions.

Most episodes improve within a few days with adequate hydration and supportive care. However, severe or persistent diarrhea can lead to dehydration and may require medical evaluation.

This evidence-based guide explains the symptoms, causes, treatment options, medications, supplements, prevention strategies, and when to seek medical advice.

What Is Diarrhea?

Q: How long does diarrhea usually last?

Most cases of viral diarrhea improve within 2–3 days , although some episodes may last up to one week.

Q: Is diarrhea contagious?

Sometimes. Diarrhea caused by viral infections, many bacterial infections, and some parasites can spread through contaminated food, water, or close personal contact. However, diarrhea caused by conditions such as food intolerances, irritable bowel syndrome (IBS), inflammatory bowel disease (IBD), medication side effects, or chronic digestive disorders is not contagious. Good hand hygiene and safe food handling help reduce the spread of infectious diarrhea.

Diarrhea is defined as passing three or more loose or watery stools within 24 hours.

It may be:

Acute – lasting less than 14 days (most common)
Persistent – lasting 2–4 weeks
Chronic – lasting longer than four weeks

The consistency, frequency, and duration of diarrhea often provide important clues to its underlying cause.

Symptoms of Diarrhea

Common symptoms include:

Frequent loose or watery stools
Urgent need to use the toilet
Abdominal cramps
Bloating
Nausea
Loss of appetite
Increased bowel sounds
Mild fever (particularly with infections)

Some people may also experience:

Vomiting
Fatigue
Weakness
Weight loss (with prolonged diarrhea)
Signs of dehydration

What Causes Diarrhea?

Diarrhea has many possible causes.

Viral Gastroenteritis

Viruses are the most common cause of acute diarrhea.

Examples include:

Norovirus
Rotavirus (especially in children)
Adenovirus
Astrovirus

Symptoms usually begin suddenly and improve within a few days.

Bacterial Infections

Food poisoning and contaminated water may cause bacterial diarrhea.

Common bacteria include:

Salmonella
Campylobacter
Shigella
Certain strains of Escherichia coli (E. coli)

Symptoms may include:

Fever
Severe abdominal pain
Bloody diarrhea

Food Intolerance

Some people develop diarrhea after consuming certain foods.

Common examples include:

Lactose intolerance
Fructose intolerance
Artificial sweeteners (such as sorbitol and xylitol)
Excess caffeine

Medications

Many medications may cause diarrhea, including:

Antibiotics
Magnesium-containing supplements and antacids
Metformin
Certain cancer treatments
Some blood pressure medications
Colchicine
Certain laxatives

Antibiotic-associated diarrhea is common because antibiotics may disrupt the normal balance of gut bacteria.

Digestive Disorders

Chronic diarrhea may occur with:

Irritable bowel syndrome (IBS-D)
Inflammatory bowel disease (Crohn’s disease and ulcerative colitis)
Celiac disease
Microscopic colitis
Pancreatic insufficiency

Stress and Anxiety

Stress does not directly cause infection, but it can increase bowel activity and worsen symptoms in people with sensitive intestines or irritable bowel syndrome.

Can Diarrhea Cause Dehydration?

Yes.

The greatest risk associated with diarrhea is dehydration, especially in:

Infants
Young children
Older adults
Pregnant women
People with chronic illnesses

Signs of dehydration include:

Dry mouth
Increased thirst
Dark urine
Passing very little urine
Dizziness
Weakness
Fatigue
Rapid heartbeat

Severe dehydration is a medical emergency.

How Is Diarrhea Diagnosed?

Most episodes of acute diarrhea do not require laboratory testing.

Your doctor may recommend further investigation if:

Symptoms last longer than one to two weeks.
Blood is present in the stool.
High fever develops.
There is severe dehydration.
Chronic diarrhea is suspected.

Possible tests include:

Stool cultures
Stool parasite examination
Blood tests
Celiac disease screening
Colonoscopy (for chronic or unexplained diarrhea)

When Should You See a Doctor?

Seek medical advice if:

Diarrhea lasts longer than 48–72 hours in adults without improvement (earlier in young children or frail older adults if symptoms are significant).
Symptoms are severe.
You cannot keep fluids down because of persistent vomiting.
Signs of dehydration develop.
You have severe abdominal pain.
Diarrhea occurs after recent antibiotic use and is severe or persistent.
You have chronic diarrhea lasting more than four weeks.

Seek urgent medical attention if you experience:

Bloody stools
Black stools
High fever
Confusion or marked drowsiness
Severe dehydration (such as very little urine, dizziness that does not improve, or fainting)

Treatment of Diarrhea

The treatment of diarrhea depends on its cause, severity, and duration. In most cases of acute diarrhea caused by viral infections, the main goals are to replace lost fluids and electrolytes, prevent dehydration, and allow the intestine to recover. Antibiotics are not needed for most episodes of acute diarrhea and should only be used when prescribed for specific bacterial infections.

Stay Hydrated

Replacing lost fluids is the most important part of treatment.

Drink small amounts frequently, especially after each loose stool.

Suitable fluids include:

Water
Oral rehydration solutions (ORS)
Clear soups and broths
Diluted fruit juice (in moderation)
Electrolyte drinks with appropriate sodium content

People at higher risk of dehydration, such as infants, older adults, and those with chronic illnesses, should pay particular attention to maintaining adequate fluid intake.

Oral Rehydration Solutions (ORS)

Oral rehydration solutions are specially formulated to replace both fluids and electrolytes lost during diarrhea.

Unlike sports drinks, ORS contains the correct balance of:

Sodium
Potassium
Glucose
Chloride

This combination improves water absorption in the intestine and helps prevent dehydration.

Commercial ORS products are recommended for:

Young children
Older adults
Moderate diarrhea
Vomiting with diarrhea
Anyone showing signs of dehydration

Electrolytes

Diarrhea causes the body to lose important electrolytes, including:

Sodium
Potassium
Chloride

Severe or prolonged diarrhea may lead to electrolyte imbalance, causing:

Muscle cramps
Weakness
Fatigue
Dizziness
Irregular heartbeat (in severe cases)

Electrolyte replacement is particularly important in children, older adults, athletes, and people experiencing prolonged diarrhea.

What Should You Eat?

Many people lose their appetite during diarrhea.

Eating small, easily digested meals is usually better than avoiding food completely.

Suitable foods include:

Rice
Bananas
Applesauce
Toast
Oatmeal
Boiled potatoes
Plain crackers
Chicken
Soup
Yogurt containing live cultures (if tolerated)

The traditional BRAT diet (Bananas, Rice, Applesauce and Toast) may provide short-term relief, but current guidelines recommend returning to a balanced diet as soon as tolerated, as prolonged restriction may delay nutritional recovery.

Foods to Avoid

Until symptoms improve, it is often advisable to avoid:

Fried foods
Fatty meals
Alcohol
Large amounts of caffeine
Highly spicy foods
Excess sugar
Sugar alcohols (sorbitol, xylitol, mannitol)
Dairy products if temporary lactose intolerance develops

These foods may worsen diarrhea or delay recovery in some individuals.

Medications for Diarrhea

Several over-the-counter and prescription medications may help relieve symptoms.

Loperamide

Loperamide slows bowel movements, allowing the intestine to absorb more water.

It may help relieve:

Traveler’s diarrhea
Acute uncomplicated diarrhea
IBS with diarrhea (IBS-D)

Do not use loperamide if:

You have bloody diarrhea.
You have a high fever.
A serious bacterial infection is suspected.
Your healthcare professional advises against it.

Bismuth Subsalicylate

Bismuth subsalicylate may help reduce:

Diarrhea
Nausea
Indigestion
Traveler’s diarrhea

It should not be used by:

People allergic to aspirin.
Children or teenagers recovering from viral infections because of the risk of Reye’s syndrome.
People taking blood-thinning medications unless advised by a healthcare professional.

Racecadotril

In some countries, racecadotril is available for the treatment of acute diarrhea.

Unlike loperamide, it reduces excessive fluid secretion into the intestine without slowing bowel movement.

It may be recommended in selected adults and children according to local guidelines.

Can Supplements Help Diarrhea?

Some supplements may support recovery, although they should not replace oral rehydration or medical treatment when needed.

Probiotics

Probiotics are among the most extensively studied supplements for diarrhea.

Certain strains may help:

Reduce the duration of infectious diarrhea.
Lower the risk of antibiotic-associated diarrhea.
Restore the balance of beneficial gut bacteria after illness.

The strongest evidence exists for specific strains, including:

Saccharomyces boulardii
Lacticaseibacillus rhamnosus GG
Selected Bifidobacterium strains

Not all probiotic products contain clinically studied strains, so choosing a high-quality supplement is important.

Zinc

Zinc plays an important role in immune function and intestinal healing.

The World Health Organization (WHO) recommends zinc supplementation for children with acute diarrhea in many low- and middle-income countries, where zinc deficiency is common, because it can reduce the duration and severity of diarrheal illness. In countries where zinc deficiency is uncommon, routine zinc supplementation for every child with diarrhea is not universally recommended, but individual circumstances may differ.

Prebiotics

Prebiotics help nourish beneficial intestinal bacteria and may support recovery of the gut microbiome after diarrhea or antibiotic treatment.

However, introducing large amounts of prebiotic fiber during acute diarrhea may temporarily worsen bloating or gas in some people. They are generally more useful after the acute illness has settled as part of long-term gut health support.

Oregano Oil

Oregano oil has antimicrobial properties and has been investigated as a complementary approach for some gastrointestinal infections and digestive disorders.

Although some laboratory studies and small clinical studies are encouraging, there is currently insufficient evidence to recommend oregano oil as a standard treatment for acute diarrhea.

Because oregano oil may also affect beneficial gut bacteria, prolonged use is not recommended without medical advice.

Amazon Products That May Help

(Affiliate Section)

⭐ Oral Rehydration Solution (ORS)

Recommended for replacing fluids and electrolytes during diarrhea.

⭐ Electrolyte Powder

Useful for adults experiencing significant fluid loss.

⭐ Probiotic Supplement

Choose products containing clinically studied strains such as:

Saccharomyces boulardii
Lacticaseibacillus rhamnosus GG
Selected Bifidobacterium strains

⭐ Digital Thermometer

Helpful for monitoring fever during gastrointestinal infections.

⭐ Heating Pad

May help relieve abdominal cramping associated with diarrhea.

Diarrhea in Children

Diarrhea is common in infants and children, most often due to viral infections such as rotavirus or norovirus. While most children recover within a few days, dehydration can develop much more quickly than in adults, making careful fluid replacement especially important.

Parents should encourage frequent small sips of oral rehydration solution (ORS) rather than plain water alone. Breastfeeding should continue whenever possible, and children who are eating solid foods should return to their normal age-appropriate diet as soon as tolerated.

Parents should seek urgent medical attention if a child:

Shows signs of dehydration (dry mouth, sunken eyes, very little urine, unusual sleepiness).
Has blood in the stool.
Has persistent vomiting and cannot keep fluids down.
Has a high fever.
Is younger than 6 months and develops significant diarrhea.
Has diarrhea lasting longer than several days or appears seriously unwell.

Anti-diarrheal medications such as loperamide should not be routinely used in young children unless specifically recommended by a healthcare professional.

Prevention

You can reduce your risk of diarrhea by:

Washing your hands thoroughly with soap and water.
Preparing and storing food safely.
Drinking clean, safe water.
Avoiding undercooked meat, seafood, and eggs.
Washing fruits and vegetables before eating.
Following food safety advice when traveling.
Taking antibiotics only when prescribed.

💊 Pharmacist’s Tip

The greatest danger during diarrhea is dehydration, not the diarrhea itself. If symptoms are mild, focus on replacing fluids and electrolytes first. If diarrhea develops after taking antibiotics, or if it lasts more than a few days, consult your doctor or pharmacist. A well-chosen probiotic may help restore the gut microbiome after infectious or antibiotic-associated diarrhea, but it should complement—not replace—adequate hydration and appropriate medical care.

How long does diarrhea usually last?

Most cases of viral diarrhea improve within 2–3 days, although some episodes may last up to one week.

Should I stop eating if I have diarrhea?

No. Eat small, easily digested meals and return to a normal balanced diet as soon as you can tolerate it.

Is diarrhea contagious?

Sometimes. Diarrhea caused by viral infections, many bacterial infections, and some parasites can spread through contaminated food, water, or close personal contact. However, diarrhea caused by conditions such as food intolerances, irritable bowel syndrome (IBS), inflammatory bowel disease (IBD), medication side effects, or chronic digestive disorders is not contagious. Good hand hygiene and safe food handling help reduce the spread of infectious diarrhea.

Can antibiotics cause diarrhea?

Yes. Antibiotics can disrupt the normal gut microbiota, leading to antibiotic-associated diarrhea.

Are probiotics helpful?

Some clinically studied probiotic strains may shorten the duration of diarrhea and help reduce antibiotic-associated diarrhea.

Can stress cause diarrhea?

Yes. Stress and anxiety can increase bowel activity, particularly in people with irritable bowel syndrome.

When should I go to the hospital?

Seek urgent medical care if you develop severe dehydration, persistent vomiting, bloody diarrhea, black stools, severe abdominal pain, confusion, or signs of shock.

Clinical Disclaimer

This article is intended for educational purposes only and should not replace professional medical advice. Consult your doctor or pharmacist if diarrhea is severe, lasts longer than a few days, is accompanied by blood in the stool, high fever, severe abdominal pain, or signs of dehydration. Infants, older adults, pregnant women, and people with weakened immune systems should seek medical advice promptly if diarrhea develops.

References

World Health Organization (WHO). Diarrhoeal Disease.
European Society for Paediatric Gastroenterology, Hepatology and Nutrition (ESPGHAN). Guidelines for the Management of Acute Gastroenteritis in Children.
American College of Gastroenterology (ACG). Clinical Guideline: Acute Infectious Diarrhea in Adults.
NICE Guideline. Diarrhoea and Vomiting Caused by Gastroenteritis in Children.
National Institute of Diabetes and Digestive and Kidney Diseases (NIDDK). Symptoms & Causes of Diarrhea.
MSD Manual Professional Edition. Acute Diarrhea.
American Gastroenterological Association (AGA). Guidelines on Probiotics and Gastrointestinal Disorders