What is causing my upset stomach and diarrhea?

Upset stomach and diarrhea can have many different causes. This article will explore the most common reasons for these unpleasant gastrointestinal symptoms and provide an overview of potential treatments and remedies.

Common Causes of Upset Stomach and Diarrhea

Some of the most frequent culprits behind an upset stomach and diarrhea include:

  • Food poisoning
  • Viral infections
  • Bacterial infections
  • Parasitic infections
  • Food intolerances
  • Stress and anxiety
  • Medication side effects
  • Inflammatory bowel diseases

Let’s explore each of these common causes in more detail:

Food Poisoning

One of the most common reasons for an upset stomach and diarrhea is food poisoning. Food poisoning occurs when you ingest food or water contaminated with bacteria, viruses, parasites, or toxins. There are more than 250 different food-borne diseases, but some of the most prevalent types of food poisoning include:

  • Salmonella – Caused by the salmonella bacteria often found in undercooked eggs, poultry, and meat.
  • E. coli – Results from eating undercooked beef, produce contaminated with fecal matter, or drinking unpasteurized milk or juice.
  • Norovirus – Extremely contagious virus transmitted through contaminated food or contact with an infected person.
  • Campylobacter – Bacteria found in undercooked poultry, unpasteurized dairy, and contaminated water.

Symptoms of food poisoning usually begin 12-48 hours after ingesting contaminated food or drink. In addition to diarrhea and vomiting, symptoms can include fever, abdominal cramps, nausea, and weakness. Food poisoning often resolves on its own within 1-3 days as the toxins pass through your system. Severe cases may require IV fluids and medication.

Viral Infections

Viruses are another common source of stomach bugs leading to nausea, vomiting, and diarrhea. Some of the viral infections that can upset your stomach and digestive system include:

  • Rotavirus – Extremely contagious virus that causes severe watery diarrhea, vomiting, fever, and abdominal pain. Mostly affects infants and young children.
  • Norovirus – Highly contagious virus causing diarrhea, vomiting, nausea, and stomach cramps. Easily transmitted through contaminated food or surfaces.
  • Adenovirus – Group of viruses that can cause cold-like symptoms, fever, and gastroenteritis leading to diarrhea and vomiting.
  • Astrovirus – Leading cause of diarrhea in babies and young kids resulting in watery diarrhea, abdominal pain, vomiting, and fever.

Viral gastroenteritis is very contagious and can spread quickly through close contact, surfaces, food, and water. Symptoms last 1-3 days and resolve on their own as your immune system fights off the virus. Severe dehydration may require medical treatment with IV fluids and antinausea medication.

Bacterial Infections

Bacterial infections in your intestinal tract can also lead to diarrhea, abdominal pain, nausea, and vomiting. Some types of bacterial gastroenteritis include:

  • Salmonella – Bacteria transmitted through contaminated poultry, eggs, beef, and dairy. Causes diarrhea, fever, and abdominal cramps.
  • E. coli – Found in undercooked beef, contaminated produce, and unpasteurized dairy. Leads to severe bloody diarrhea and vomiting.
  • Campylobacter – Passed on through contaminated poultry, dairy, and water. Results in diarrhea, cramps, fever, and nausea.
  • Clostridium difficile – Overgrowth of bacteria often after antibiotic treatment. Causes watery diarrhea, abdominal pain, nausea, and fever.

Bacterial gastroenteritis is generally self-limiting, resolving within a few days as the bacteria pass through the intestines. However, some types like E. coli and C. difficile can cause severe infections requiring medical treatment and fluids.

Parasitic Infections

Intestinal parasites can invade your gastrointestinal tract and cause persistent diarrhea, nausea, bloating, pain, and weight loss. Some examples of parasitic infections leading to stomach upset include:

  • Giardia – One of the most common parasitic causes of diarrhea contracted through contaminated food and water sources. Results in greasy foul-smelling diarrhea, gas, bloating, nausea, and cramps.
  • Cryptosporidium – Parasite that spreads through contaminated water and surfaces. Causes watery diarrhea, cramps, nausea, vomiting, fever, and weight loss.
  • Cyclospora – Parasite transmitted on contaminated produce. Symptoms include explosive diarrhea, bloating, fatigue, loss of appetite, and substantial weight loss.

Antiparasitic medication is required to eradicate most intestinal parasites. Preventing dehydration and malnutrition with IV fluids and diet modification may be necessary with severe symptoms.

Food Intolerances

Food intolerances occur when your body lacks the enzymes needed to properly digest certain foods. This results in abdominal discomfort, diarrhea, bloating, and nausea after eating the offending food. Some of the most common food intolerances include:

  • Lactose Intolerance – Inability to break down lactose sugars in dairy products. Symptoms of bloating, cramps, gas, and diarrhea typically begin 30 minutes to 2 hours after consuming milk or dairy foods.
  • Fructose Intolerance – Inability to absorb fructose sugar properly. Fructose is found naturally in fruits and honey and as an added sweetener. Symptoms include bloating, diarrhea, nausea, and gas after ingesting fructose.
  • Gluten Intolerance – Difficulty digesting gluten proteins found in wheat, barley, and rye. Can cause abdominal pain, bloating, chronic diarrhea, and nutrient malabsorption.

The primary treatment for food intolerances involves removing the problematic foods from your diet. Digestive enzyme supplements may also help improve digestion and reduce symptoms.

Stress and Anxiety

Your brain and digestive system have a strong two-way connection regulated by the enteric nervous system. During times of stress and anxiety, this communication network gets disrupted which can lead to stomach upset and diarrhea. Some ways stress impacts your digestion include:

  • Increased stomach acid production leading to indigestion, heartburn, and nausea.
  • Altered intestinal contractions resulting in accelerated transit time and loose stools.
  • Suppressed immune system increasing susceptibility to infections that cause diarrhea.
  • Altered gut microbiome allowing for opportunistic bacterial overgrowth.

Managing emotional health through relaxation techniques, mindfulness, therapy, medication, and social support can relieve stress-related stomach upset. Antacids and antidiarrheals may provide symptom relief during flare-ups.

Medication Side Effects

Many different types of medications can negatively impact digestion and lead to diarrhea as a side effect. Some major drug classes that may cause diarrhea include:

  • Antibiotics – Disrupt natural gut microbes allowing for opportunistic infections.
  • NSAIDs – Cause gastrointestinal erosion and ulcers leading to bleeding and diarrhea.
  • Blood pressure medications – Impact electrolyte absorption resulting in loose stools.
  • Chemotherapy drugs – Damage intestinal mucosa causing diarrhea.
  • Antacids with magnesium – Excess magnesium acts as an osmotic laxative.

Switching medications or taking anti-diarrheal drugs may alleviate medication-related diarrhea. Always talk to your doctor before stopping or changing prescribed medications.

Inflammatory Bowel Diseases

Chronic inflammatory bowel diseases like Crohn’s disease and ulcerative colitis are characterized by persistent gastrointestinal symptoms. Diarrhea, abdominal pain, cramping, reduced appetite, nausea, fatigue, and unintended weight loss are common. These diseases cause a misdirected immune response leading to intestinal inflammation, ulcers, scarring, and dysfunction.

While inflammatory bowel diseases cannot be cured, various medications can induce remission and minimize symptoms. Diet modifications, probiotics, surgery, and nutritional supplements also help manage these chronic gastrointestinal conditions.

Diagnosing the Cause of Diarrhea

To get to the root cause of your upset stomach and diarrhea, your doctor will typically:

  • Ask about your symptoms and medical history
  • Perform a physical exam checking for signs of dehydration, fever, or abdominal tenderness
  • Order laboratory tests on your blood, stool, or gastric samples
  • Conduct imaging tests like abdominal X-rays, CT scans, or endoscopies

Identifying any related infections, inflammation, structural abnormalities, or other issues allows your doctor to make a definitive diagnosis and recommend appropriate treatment options.

Treating and Preventing Diarrhea

Treatment for diarrhea focuses on staying hydrated, managing symptoms, and addressing any underlying cause. Some general treatment guidelines include:

  • Drinking plenty of water, broths, or electrolyte-rich sports drinks
  • Getting plenty of rest to allow your body to heal
  • Eating small, bland, low-fiber meals like the BRAT diet
  • Taking over-the-counter anti-diarrhea or antinausea medication
  • Using probiotic supplements to restore gut microflora
  • Taking prescribed antibiotics to treat bacterial infections
  • Following a parasite cleanse protocol if parasites are the issue

Preventing future occurrences involves maintaining optimal gastrointestinal health through:

  • Practicing good hygiene when handling food
  • Only consuming pasteurized dairy products
  • Cooking meats thoroughly and avoiding cross-contamination
  • Washing all fruits and vegetables thoroughly
  • Drinking only purified water when traveling
  • Managing stress levels through lifestyle changes
  • Taking probiotics to support healthy gut flora

Seeking prompt medical care when diarrhea lasts more than 2 days or is accompanied by severe pain, bleeding, fever, dehydration, or other concerning symptoms can also prevent complications.

When to See a Doctor

You should seek medical evaluation for diarrhea when:

  • Diarrhea lasts more than 2 days or keeps recurring
  • You observe blood or mucus in the stool
  • You have a fever over 101 F
  • You have severe rectal pain
  • You have signs of dehydration like excessive thirst, infrequent urination, racing heart rate, dizziness, or dark urine
  • You have recently taken antibiotics
  • You have recently traveled internationally
  • You have a weakened immune system or serious medical condition
  • Your diarrhea is not improving with over-the-counter remedies

Rapid evaluation and treatment by a medical professional can help identify and resolve the cause of your diarrhea while preventing dangerous complications from dehydration and malnutrition.

When to Go to the Emergency Room

Seek emergency medical care if you experience:

  • Bloody or black tarry stools
  • Severe constant abdominal pain
  • Fever over 102 F
  • Confusion, weakness, or dizziness indicating dehydration
  • Inability to keep down fluids due to unrelenting vomiting
  • Recent antibiotic use and signs of severe colitis

Life-threatening dehydration, electrolyte imbalances, bowel perforation, sepsis, or other dangerous complications can arise from severe cases of diarrhea. Getting emergency treatment can be critical for stabilizing your condition.


Diarrhea and upset stomach have many potential causes including infections, food intolerances, inflammatory diseases, parasites, medications, and stress. Staying hydrated and getting adequate rest are key during acute episodes. Seeking prompt medical attention when diarrhea is severe or accompanied by concerning symptoms allows for proper diagnosis and treatment to relieve your discomfort and prevent complications.

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