The most effective over-the-counter medicine to stop diarrhea is loperamide, sold as Imodium A-D. It slows movement through your intestines, giving your body more time to absorb water and firm up your stool. For most adults with uncomplicated diarrhea, loperamide works within an hour or two of the first dose. Bismuth subsalicylate (Pepto-Bismol) is a second option that works differently, reducing inflammation and killing some bacteria in the gut, though it’s generally slower-acting.
Loperamide: The Fastest OTC Option
Loperamide is the go-to for acute diarrhea in adults and teenagers. The standard approach is to take two tablets (4 mg) after your first loose bowel movement, then one tablet (2 mg) after each subsequent loose stool. The FDA sets the maximum at 8 mg per day for over-the-counter use, which means no more than four tablets in 24 hours. Exceeding this limit is dangerous and can cause serious heart problems.
Loperamide works by slowing the muscles in your intestinal wall so contents move through more gradually. This gives the lining of your gut more time to pull water back into your body instead of losing it in watery stool. It doesn’t treat the underlying cause of diarrhea. It manages the symptom while your body fights off whatever triggered it.
Bismuth Subsalicylate: A Gentler Alternative
Pepto-Bismol and similar products containing bismuth subsalicylate take a different approach. Rather than slowing your gut, they coat the intestinal lining and reduce the irritation driving the diarrhea. They also have mild antibacterial properties, which is why bismuth subsalicylate is sometimes recommended for traveler’s diarrhea prevention.
The tradeoff is speed. Bismuth subsalicylate typically takes longer to produce noticeable results compared to loperamide. It can also turn your tongue and stool black, which is harmless but alarming if you’re not expecting it. Because it contains a compound related to aspirin, it’s not safe for children under 12 or anyone who shouldn’t take aspirin.
When You Should Not Take Anti-Diarrheal Medicine
Diarrhea is sometimes your body’s way of flushing out something harmful, and stopping it prematurely can make things worse. Do not take loperamide if you have blood in your stool along with a high fever, as the NHS notes these can be signs of dysentery or a serious bacterial infection. In those cases, your body needs to expel the bacteria, and slowing your gut down traps the infection inside.
If your diarrhea lasts more than two days while taking over-the-counter medicine, it’s time to see a doctor. The National Institute of Diabetes and Digestive and Kidney Diseases uses that two-day mark as the threshold where self-treatment should stop and professional evaluation should start. Bloody or black stool, a fever of 102°F or higher, confusion, or an inability to keep fluids down are all signals that something more serious is going on.
Prescription Options for Persistent Problems
If your diarrhea is caused by a specific condition rather than a passing stomach bug, your doctor may prescribe something targeted. One common prescription is rifaximin, an antibiotic used specifically for traveler’s diarrhea caused by E. coli and for irritable bowel syndrome with diarrhea (IBS-D). It works locally in the gut, killing problem bacteria without being absorbed much into the rest of your body.
For IBS-D that doesn’t respond to other treatments, other prescription medications can reduce the frequency and urgency of episodes by acting on the nerves and muscles in your intestines. These are not first-line treatments. They’re reserved for people whose chronic diarrhea significantly impacts daily life.
Hydration Matters More Than Medicine
The biggest risk from diarrhea isn’t the diarrhea itself. It’s dehydration. Every loose stool pulls water and electrolytes out of your body, and if you’re not replacing them, you can become dehydrated quickly. Signs to watch for in adults include skin that stays tented when you pinch it instead of flattening back, sunken eyes, and confusion. In infants, look for a rapid heart rate, sunken soft spot on the skull, and no tears when crying.
Water alone isn’t ideal for rehydration because it doesn’t replace the salt and potassium you’re losing. The World Health Organization’s oral rehydration formula is simple enough to make at home: about 4 cups of water, half a teaspoon of salt, and 2 tablespoons of sugar. The sugar isn’t just for taste. It activates a transport mechanism in your intestinal cells that pulls sodium and water into your body far more efficiently than water alone. You can also make a version with 3/4 cup of 100% apple or grape juice diluted in about 3 1/4 cups of water with half a teaspoon of salt. Commercial products like Pedialyte follow the same principle.
Probiotics Can Shorten Recovery
Probiotics won’t stop diarrhea the way loperamide does, but they can reduce how long an episode lasts. A large meta-analysis of randomized trials in children found that Saccharomyces boulardii, a yeast-based probiotic, shortened diarrhea duration by about 1.25 days compared to placebo. Certain Lactobacillus and Bifidobacterium strains also showed meaningful reductions of roughly one day.
These aren’t dramatic effects, but shaving a full day off a bout of diarrhea is meaningful when you’re miserable. Look for products that specifically list Saccharomyces boulardii or Lactobacillus reuteri on the label. Generic “probiotic blend” products may not contain strains with strong evidence behind them.
What to Eat While Recovering
You’ve probably heard of the BRAT diet: bananas, rice, applesauce, and toast. It’s a reasonable starting point for the first day or two, but there’s no need to limit yourself to just those four foods. Brothy soups, oatmeal, boiled potatoes, crackers, and unsweetened dry cereals are equally gentle on your stomach. The key is choosing bland, low-fiber foods that won’t further irritate your gut.
Once your stomach settles, start adding foods with more nutritional value. Cooked carrots, sweet potatoes without skin, avocado, skinless chicken, fish, and eggs are all easy to digest while providing the protein and nutrients your body needs to recover. Sticking with only bananas and white rice for days on end, as Harvard Health Publishing points out, leaves you short on the calories and nutrients that actually help you bounce back.
Children Need a Different Approach
Loperamide is available for children in liquid form, but it should not be given to kids under 2 years old, and many pediatricians advise against it for younger children in general. Bismuth subsalicylate is off-limits for children under 12 due to the risk of Reye’s syndrome, a rare but serious condition linked to aspirin-related compounds in young people.
For children, the priority is hydration rather than stopping the diarrhea with medication. Oral rehydration solutions designed for kids (like Pedialyte) replace fluids and electrolytes in the right proportions. Probiotics, particularly Saccharomyces boulardii, have the strongest evidence in pediatric populations and are generally safe. If a child has diarrhea lasting more than 24 hours, can’t keep fluids down, or shows signs of dehydration like no wet diapers for three hours, that warrants a call to their doctor.