The two most effective over-the-counter medicines for diarrhea are loperamide (sold as Imodium) and bismuth subsalicylate (sold as Pepto-Bismol and Kaopectate). They work differently, so the best choice depends on your symptoms and what’s causing them. Beyond these two standbys, probiotics, prescription antibiotics, and other medications may help depending on whether your diarrhea is a short-lived stomach bug, a side effect of antibiotics, or a chronic problem.
Loperamide: The Fastest OTC Option
Loperamide works by slowing down the movement of your intestines, giving them more time to absorb water from digested food. This means firmer stools and fewer trips to the bathroom. It’s the strongest anti-diarrheal you can buy without a prescription.
The standard approach for adults is to take two capsules (4 mg total) after your first loose bowel movement, then one capsule (2 mg) after each additional loose stool. The daily maximum is 8 capsules (16 mg) in 24 hours. Most people find relief within an hour of the first dose.
Loperamide is safe at recommended doses, but the FDA has issued warnings about taking significantly more than directed. Very high doses can cause dangerous heart rhythm problems, and reports of cardiac arrest and death have been linked to intentional misuse. Stick to the label instructions, and if symptoms don’t improve within two days, stop taking it and talk to a doctor rather than increasing your dose.
One important caveat: loperamide is best for watery, non-bloody diarrhea. If you have a fever, bloody stools, or signs of a bacterial infection, slowing your gut down can actually trap the pathogen inside longer. In those cases, bismuth subsalicylate or medical evaluation is a better route.
Bismuth Subsalicylate: Gentler and Broader
Bismuth subsalicylate treats diarrhea while also helping with nausea, heartburn, and general stomach upset. That makes it a good pick when diarrhea comes with other digestive symptoms, like the kind you get from food that didn’t agree with you or mild traveler’s stomach.
Adults and teenagers can take 2 tablets (or 2 tablespoonfuls of liquid) every 30 minutes to an hour as needed. Don’t exceed 16 tablets or 16 tablespoonfuls of regular-strength liquid in 24 hours. It works more gradually than loperamide, coating and calming the digestive tract rather than slowing it mechanically.
This medication contains a compound related to aspirin, which means it carries a risk of Reye’s syndrome in children and teenagers recovering from viral infections like the flu or chickenpox. Don’t give it to kids in those situations. It can also temporarily turn your tongue and stools black, which is harmless but can be alarming if you’re not expecting it.
Probiotics for Antibiotic-Related Diarrhea
If your diarrhea started after you began a course of antibiotics, probiotics are worth considering. Two strains have the strongest evidence behind them: Lactobacillus rhamnosus GG (often labeled LGG) and Saccharomyces boulardii, a beneficial yeast.
The numbers are encouraging. In a large analysis of over 4,700 adults and children, Saccharomyces boulardii cut the rate of antibiotic-associated diarrhea roughly in half, from about 17% to 8% in adults and from 21% to 9% in children. LGG showed similar results, reducing the risk from about 22% to 12% across nearly 1,500 participants. In children specifically, adequate doses of LGG reduced the risk of antibiotic-associated diarrhea by 71%.
For acute infectious diarrhea (stomach bugs), both strains shortened the duration of illness by about a day. That may not sound dramatic, but when you’re miserable, one fewer day matters. The effective dose in studies was generally at least 10 billion colony-forming units (CFU) per day for 5 to 10 days. Look for products that list the specific strain and CFU count on the label, not just “probiotic blend.” Starting probiotics at the same time as your antibiotic course, rather than waiting until diarrhea develops, appears to be the most effective approach.
Prescription Medicines for Severe Cases
When OTC options aren’t enough, doctors have several prescription tools. One common choice is a combination pill containing diphenoxylate and atropine, which works similarly to loperamide by slowing gut motility. The atropine is added in a tiny, sub-therapeutic amount specifically to discourage misuse. This is typically reserved for adults and teenagers 13 and older whose diarrhea hasn’t responded to simpler measures.
Traveler’s Diarrhea
Traveler’s diarrhea often involves bacterial infections picked up from contaminated food or water, and antibiotics can cut recovery time significantly. The CDC lists several options depending on where you traveled. Azithromycin is the preferred treatment when diarrhea involves fever or bloody stools, and it’s the first-line choice for infections picked up in Southeast Asia, where resistance to other antibiotics is common. A single 1,000 mg dose (sometimes split into two doses the same day to reduce nausea) is often enough, though a three-day course at a lower dose is an alternative.
Fluoroquinolones like ciprofloxacin have traditionally been the go-to antibiotics, but rising bacterial resistance, particularly from Campylobacter in Asia, has limited their usefulness in many regions. Rifaximin is another option approved for diarrhea caused by non-invasive E. coli strains, typically taken over three days. Doctors sometimes combine an antibiotic with loperamide for faster symptom control.
Chronic Diarrhea From Bile Acid Malabsorption
If you’ve had persistent, watery diarrhea for weeks or months without an obvious infection, one underdiagnosed cause is bile acid malabsorption. Your liver produces bile acids to help digest fat, and normally your small intestine reabsorbs most of them. When that recycling process fails, excess bile acids reach your colon and trigger watery diarrhea.
The first-line treatment is a class of medications called bile acid binders, most commonly cholestyramine or colestipol. These are positively charged molecules that latch onto bile acids in your intestine, preventing them from irritating your colon. Colesevelam is a newer alternative that some people find easier on the stomach. These medications often produce noticeable improvement within days.
What Your Symptoms Tell You
Not all diarrhea needs medicine. A brief bout from a mild stomach virus or something you ate will usually resolve on its own in a day or two. Staying hydrated is the most important thing you can do during that window. Water is fine for mild cases, but if diarrhea is frequent or heavy, an oral rehydration solution or drinks with electrolytes will replace what you’re losing more effectively.
Certain symptoms signal that self-treatment isn’t appropriate. See a doctor if your diarrhea lasts more than two days, if you notice blood or black color in your stools, if you develop a fever above 101°F (38°C), or if you have severe abdominal or rectal pain. Dehydration is the other major red flag: dark urine, dizziness, dry mouth, or feeling faint all mean you need medical help. For children, the timeline is shorter. A child whose diarrhea doesn’t improve within 24 hours, or who shows any of these warning signs, needs to be seen promptly.