Medical Information & Safety Disclaimer: This guide is for educational purposes only. It is not a diagnosis, treatment plan, or medical advice. Always consult a qualified clinician about your health concerns. Seek immediate care for severe, sudden, or worsening symptoms.

Diarrhea: Possible Causes, Red Flags & When to Seek Care

Diarrhea is characterized by abnormally loose, watery, or frequent bowel movements (typically three or more times in a single day). It occurs when the intestines do not absorb enough fluid, or secrete too much fluid, causing waste to pass through the digestive tract too quickly. Diarrhea is an extremely common symptom that can be acute (lasting a few days) or chronic (lasting several weeks). Most acute cases are caused by temporary viral, bacterial, or parasitic infections, or dietary changes. However, chronic diarrhea can be a sign of inflammatory bowel diseases, food intolerances, or irritable bowel syndrome. The primary risk associated with diarrhea is dehydration, which makes monitoring fluid intake crucial.

Quick Summary Box

Possible Causes Include

Viral or bacterial infection (gastroenteritis), Dietary triggers or food intolerances, Medication side effects

Warning Signs (Red Flags)

Sudden severity, chest pressure, difficulty breathing, confusion, or weakness.

When to Seek Care

Seek urgent care for emergency signs. Consult primary care if symptoms persist beyond a few days.

What to Track

Record onset, triggers, pain levels (1-10), and response to self-care or medications.

What diarrhea may feel like

Diarrhea involves loose, liquid stools accompanied by an urgent, sometimes uncontrollable need to have a bowel movement. It is often preceded or accompanied by cramping, bloating, or a rumbling noise in the lower abdomen (borborygmi). You may also experience mild nausea, a feeling of incomplete emptying, and generalized weakness. If caused by an infection, you might also have a low-grade fever, chills, and body aches.

Common possible causes of diarrhea

The following are common reasons someone might experience this symptom. This list is for educational context only and does not represent a diagnosis. A proper clinical assessment is required to identify the root cause.

Viral or bacterial infection (gastroenteritis)

Pathogens from contaminated food or water, or close contact with an infected person, invade the intestinal lining, disrupting normal fluid absorption and causing secretion of excess fluids.

Why it may fit: Possible if the diarrhea starts suddenly, is watery, and is accompanied by stomach cramps, low fever, or nausea.

When to seek care: Drink plenty of fluids containing electrolytes. Seek care if diarrhea lasts longer than two days in adults, or if you develop signs of dehydration.

Dietary triggers or food intolerances

Inability to properly digest certain substances, such as lactose (milk sugar) or artificial sweeteners (sorbitol), which draw excess water into the bowel, or consuming very spicy or greasy foods.

Why it may fit: Possible if the loose stools occur within a few hours of eating specific foods (like dairy or sugar-free candy) and resolve once those foods are avoided.

When to seek care: Keep a food diary to identify and eliminate trigger foods. Consult a doctor or dietitian if symptoms persist or restrict your diet significantly.

Medication side effects

Certain medications, particularly antibiotics, can disrupt the natural balance of beneficial bacteria in your gut, allowing harmful bacteria to flourish or affecting bowel motility.

Why it may fit: Possible if the diarrhea begins within a few days of starting a new medication, especially an antibiotic course.

When to seek care: Do not stop taking prescribed medications without consulting your doctor. A healthcare provider can recommend adjustments or probiotics if appropriate.

Red flags: when to seek urgent care

Urgent Medical Attention Required

Certain symptoms can indicate a serious or life-threatening condition that requires immediate medical evaluation. Seek emergency care (call 911 or visit the nearest ER) if you experience diarrhea alongside any of the following signs:

⚠ Diarrhea containing blood, pus, or resembling black tar
⚠ Diarrhea accompanied by a high fever (above 102°F or 38.9°C)
⚠ Severe, persistent abdominal pain that is not relieved by a bowel movement
⚠ Signs of severe dehydration: extreme thirst, dry mouth, little to no urination, dark urine, confusion, or dizziness
⚠ Diarrhea that does not improve after 48 hours (or 24 hours in children)
⚠ Diarrhea in an individual with a weakened immune system or chronic illness

What to track before seeing a doctor

To help your healthcare provider make a more accurate diagnosis, it is highly recommended to monitor and record detailed information about your symptom. Use this checklist as a guide:

✓ Log the frequency, consistency, and color of your bowel movements.
✓ Monitor your hydration status: track the volume of liquids you drink and how often you urinate.
✓ Note if you have a fever, abdominal pain, or blood in your stool.
✓ Keep a list of all foods, drinks, and medications consumed in the 24 hours before symptoms started.

Questions a doctor may ask you

During a clinical examination, a doctor or healthcare provider will ask detailed questions to narrow down the possible causes. Being prepared for these questions helps ensure a productive consultation:

? How many loose stools are you having per day, and what is their appearance?
? Have you recently traveled internationally, eaten raw or undercooked foods, or been exposed to anyone with similar symptoms?
? Have you recently taken antibiotics or started any new medications?

Frequently asked questions about diarrhea

Antibiotics are designed to kill harmful bacteria, but they also destroy the beneficial bacteria that inhabit your intestines. This disruption of the gut microbiome can alter digestion, reduce the gut's ability to absorb water, and sometimes allow opportunistic bacteria like Clostridioides difficile (C. diff) to overgrow, causing diarrhea.

The BRAT diet stands for Bananas, Rice, Applesauce, and Toast. These are bland, low-fiber foods that are easy on the stomach. While helpful for a short period to ease back into eating, medical experts now recommend resuming a normal, balanced diet as soon as you feel able, as the BRAT diet lacks sufficient nutrients, protein, and fats to promote healing.

Drink fluids that contain water, salts, and simple sugars, such as oral rehydration salts (ORS), sports drinks, broths, or diluted juices. Avoid plain water in large quantities, as it does not replace lost electrolytes. Avoid caffeine, alcohol, and very sugary drinks, which can make diarrhea worse.