Loperamide (sold as Imodium) is the most effective over-the-counter anti-diarrhea medicine for adults, and it’s the one most doctors recommend for common, non-infectious diarrhea. It works by slowing down the movements of the intestines, giving your body more time to absorb water and firm up your stool. For milder cases, or when nausea and stomach upset are also in the picture, bismuth subsalicylate (Pepto-Bismol) is a solid second option.
Which one you should reach for depends on what’s causing the diarrhea, how severe it is, and who’s taking it.
Loperamide: The Strongest OTC Option
Loperamide is the go-to for fast relief from acute diarrhea. The standard adult dose is two caplets (4 mg) after the first loose bowel movement, then one caplet (2 mg) after each subsequent loose stool. The daily maximum is typically 8 mg for OTC use (4 tablets), though the capsule form allows up to 16 mg under a doctor’s guidance.
It’s effective for diarrhea caused by food intolerances, stress, mild stomach bugs, and general digestive upset. It does not treat the underlying cause. It simply buys your gut time to recover. Most people notice a significant reduction in loose stools within a few hours.
One important note: you should not take loperamide if you have a fever, bloody stools, or suspect a bacterial infection. In those cases, slowing down your intestines can actually trap harmful bacteria inside, making things worse.
Bismuth Subsalicylate: A Gentler Alternative
Bismuth subsalicylate handles diarrhea differently. Rather than slowing gut movement directly, it reduces inflammation in the intestinal lining and has mild antimicrobial properties. It’s a better fit when your diarrhea comes with nausea, heartburn, or an upset stomach, since it treats all of those at once.
The tradeoff is that it’s less potent than loperamide for stopping frequent loose stools. It also comes with a harmless but startling side effect: it can temporarily turn your tongue dark and your stools grayish-black. This goes away once you stop taking it.
Bismuth subsalicylate contains a compound related to aspirin. That means it’s not safe for children under 16, because salicylates carry a small risk of Reye’s syndrome, a rare but serious condition that causes brain swelling in children recovering from viral illnesses. Anyone with an aspirin allergy or who takes blood thinners should also avoid it.
Prescription Medicines for Chronic Diarrhea
If over-the-counter options aren’t enough, or if diarrhea is an ongoing problem rather than a one-time episode, prescription medications exist for specific conditions. People with irritable bowel syndrome with diarrhea (IBS-D), for example, may be prescribed eluxadoline, which targets the gut’s nervous system to reduce cramping and loose stools. Diphenoxylate-atropine (Lomotil) is another prescription anti-diarrheal that works similarly to loperamide but at a stronger level.
These aren’t medications you’d pick up for a bad day. They’re reserved for people with a diagnosed condition who need daily or recurring management.
When Antibiotics Are the Right Medicine
Sometimes the best anti-diarrhea medicine isn’t an anti-diarrheal at all. If a bacterial infection is driving the problem, particularly with traveler’s diarrhea, antibiotics may be the appropriate treatment. The CDC classifies traveler’s diarrhea into three tiers: mild cases that don’t interfere with your day (no antibiotic needed), moderate cases that disrupt your plans, and severe cases that are incapacitating. Antibiotics are recommended for moderate to severe cases.
Azithromycin is the preferred first-line antibiotic, especially for travelers in Southeast Asia or anywhere antibiotic-resistant bacteria are common. It’s also the go-to when stools are bloody or a fever is present. Other antibiotics like rifaximin are reserved for non-invasive infections, meaning diarrhea caused by certain strains of E. coli without signs of deeper tissue involvement. These are all prescription-only and typically require a travel medicine consultation before your trip or a doctor visit if you’re already sick.
Rehydration Matters More Than Medicine
No matter which medicine you choose, replacing lost fluids is the single most important thing you can do during a bout of diarrhea. Water alone isn’t ideal because diarrhea flushes out electrolytes, especially sodium and potassium, along with fluid. An oral rehydration solution restores both. The World Health Organization’s formula is simple: about 4 cups of water, half a teaspoon of salt, and 2 tablespoons of sugar. The sugar isn’t just for taste. It helps your intestines absorb the sodium and water more efficiently.
Store-bought options like Pedialyte or Drip Drop follow the same principle. Sports drinks like Gatorade are less effective because they contain too much sugar relative to sodium, but they’re better than nothing if that’s what you have on hand.
Probiotics as a Supplement
Probiotics aren’t a replacement for anti-diarrheal medication, but they can help. A meta-analysis in The Lancet found that probiotics reduced the risk of antibiotic-associated diarrhea by 52% and acute diarrhea from various causes by 34%. In children, the reduction was even more pronounced, at 57%. Strains like Saccharomyces boulardii and Lactobacillus rhamnosus GG are the most studied, though the analysis found no major difference in effectiveness between individual strains.
If you’re taking antibiotics and want to reduce the chance of diarrhea as a side effect, starting a probiotic alongside your antibiotic course is a reasonable strategy.
What to Eat During Diarrhea
You may have heard of the BRAT diet: bananas, rice, applesauce, and toast. It’s been a home remedy for decades, but medical organizations including the American Academy of Pediatrics and the CDC no longer recommend it. The diet is too restrictive and can actually impair nutritional recovery. Clinical trials show that resuming a normal, varied diet as soon as you’re rehydrated leads to shorter illness duration, lower stool output, and better nutritional outcomes compared to gradually reintroducing bland foods.
The practical takeaway: eat what you can tolerate, and aim for a mix of foods rather than limiting yourself to four bland options. If greasy or spicy foods make you feel worse, skip those temporarily, but don’t starve yourself or eat only crackers for three days.
Treating Children Safely
Children need a different approach. The American Academy of Pediatrics recommends oral rehydration as the primary treatment, not medication. Children should be given an oral rehydration solution within three to four hours of symptom onset. Breastfed infants should continue breastfeeding, and formula-fed infants should stick with their regular formula at normal strength. A regular diet should resume as soon as dehydration is corrected.
Loperamide is not recommended for children under 2 and should only be used in older children under medical guidance. Bismuth subsalicylate is off-limits for anyone under 16 due to the Reye’s syndrome risk. For children, the focus should be on fluids and food, not pharmacology.
Signs That Need Medical Attention
Most diarrhea resolves on its own within a day or two. In adults, it’s time to see a doctor if diarrhea persists beyond two days without improvement, if you notice blood or black color in your stool, if you develop a fever above 102°F, or if you’re showing signs of dehydration: excessive thirst, dark urine, dizziness, or very little urination. Severe diarrhea, defined as more than 10 bowel movements a day or fluid losses that clearly exceed what you’re drinking, warrants prompt medical care.
For children, the timeline is shorter. Diarrhea that doesn’t improve within 24 hours, no wet diaper for three or more hours, a fever above 102°F, bloody or black stools, or unusual sleepiness or irritability all warrant a call to the pediatrician. Sunken eyes, cheeks, or a soft spot on an infant’s head, or skin that stays tented when you gently pinch it, are signs of significant dehydration that need immediate attention.