Acute diarrhea: What to do fast and when to see a doctor

Acute diarrhea can ruin your day — and dehydrate you fast. Here’s simple, practical help you can use right away, plus clear signs that mean you need medical care.

Most cases start suddenly and last a few days. Viral infections (like norovirus or rotavirus), food poisoning, and travel-related bacteria are the usual suspects. Symptoms include loose or watery stools, stomach cramps, nausea, and sometimes low fever. The biggest immediate risk is losing too much fluid and salts.

Quick self-care

Drink fluids before you feel thirsty. Water is okay, but oral rehydration solutions (ORS) replace salts and sugar too, which helps your body absorb water. For adults, sip 200–400 ml after each loose stool. For children follow packet instructions or ask a pharmacist. Avoid sugary drinks, alcohol, and caffeine — they can make diarrhea worse. Eat bland foods when you can: bananas, rice, applesauce, toast.

For adults with sudden watery diarrhea and no fever or blood, loperamide can reduce stool frequency. Typical OTC dosing is 4 mg to start, then 2 mg after each loose stool, up to 8 mg in 24 hours unless a doctor advises otherwise. Don’t give loperamide to children under two and check a doctor before use in young kids. If you have high fever, bloody stools, or suspect certain bacterial infections, antibiotics are not routine and should only be used if a doctor identifies a bacterial cause. For traveler's diarrhea, a short course of azithromycin or rifaximin may be recommended by a clinician.

Wash hands with soap after using the toilet and before eating. Drink bottled or boiled water when you travel to places with unsafe water. Avoid raw seafood, undercooked meat, and food from unreliable vendors.

When to seek medical help

Call your doctor or go to ER if you have severe belly pain, blood in stool, high fever over 38.5°C (101.3°F), signs of severe dehydration (dizziness, very little urine, fast heartbeat), or if diarrhea lasts more than 48 hours in adults or 24 hours in infants. Babies, elderly people, and those with weakened immune systems should be evaluated sooner.

If symptoms are severe, last longer than a few days, or include blood, your doctor may order stool tests, blood work, or imaging to find the cause. Treatment then targets the identified bug or condition.

Probiotics can help in some cases. Saccharomyces boulardii or Lactobacillus rhamnosus strains may shorten diarrhea by a day or two. Typical over-the-counter doses are listed on product labels; follow them and talk to your pharmacist if you are pregnant or immunocompromised. Avoid routine anti-diarrheal drugs if you have high fever or bloody stools. When in doubt, a quick call to your clinic can save time and prevent complications.

Keep a rehydration sachet at home and refill it after you recover again soon. Keep fluids handy and stay alert.