The two most effective over-the-counter medicines for diarrhea are loperamide (sold as Imodium A-D) and bismuth subsalicylate (sold as Pepto-Bismol). Both reduce the flow of fluids into your bowels, but they work differently and are suited to slightly different situations. For most healthy adults with a sudden bout of diarrhea, either one will help.
Loperamide: The Strongest OTC Option
Loperamide is the more targeted of the two. It activates receptors in your gut wall that slow down the muscle contractions pushing food through your intestines. This gives your body more time to absorb water from stool, making bowel movements less frequent and less watery. It only treats diarrhea and nothing else.
The standard adult dose is two caplets (4 mg) after your first loose bowel movement, then one caplet (2 mg) after each subsequent loose stool. The over-the-counter tablet version caps out at 8 mg (four tablets) in 24 hours, while prescription or capsule forms allow up to 16 mg per day. Don’t exceed the limit on the package. Loperamide works quickly, often within an hour, and is a good choice when you need to get through a workday or travel.
Bismuth Subsalicylate: For Diarrhea Plus Nausea
Bismuth subsalicylate takes a different approach. It reduces inflammation in your intestinal lining and has mild antibacterial properties. It’s less powerful at stopping diarrhea on its own compared to loperamide, but it pulls double duty: it also treats nausea, heartburn, and indigestion. If your diarrhea comes with an upset stomach, this is the better pick.
One important restriction: bismuth subsalicylate contains a compound related to aspirin. Children and teenagers under 16 should not take it, especially during or after a viral illness like the flu or chickenpox, because of the risk of Reye’s syndrome. This is a rare but serious condition where the liver stops filtering toxins properly, allowing ammonia to build up in the blood and damage the brain.
What to Eat and Drink While You Recover
Medicine alone won’t resolve diarrhea if your diet is working against you. While symptoms are active, avoid these categories of food and drink:
- Caffeine (coffee, tea, energy drinks) and alcohol, both of which stimulate your gut
- High-fat foods like fried food, pizza, and fast food
- High-sugar drinks and foods, including fruit juices, candy, and packaged desserts with fructose
- Sugar alcohols found in sugar-free gum and candies (these are notorious for pulling water into the intestines)
- Dairy products containing lactose, which can be harder to digest during and even for a month after a bout of diarrhea
Your top priority is replacing lost fluids. Dehydration is the main danger of diarrhea, not the diarrhea itself. Drink water steadily throughout the day. Oral rehydration solutions or broths help replace the sodium and potassium you’re losing. Signs you’re getting dehydrated include excessive thirst, dark urine, dry mouth, dizziness, and lightheadedness.
Probiotics as a Supplement
Certain probiotic strains can shorten a bout of diarrhea, particularly when the cause is infectious. The two with the most clinical evidence are Lactobacillus rhamnosus GG and the yeast Saccharomyces boulardii. In clinical trials, Saccharomyces boulardii reduced the likelihood of diarrhea lasting four or more days by roughly 60%. Lactobacillus GG showed even stronger effects in children with rotavirus, cutting stool frequency significantly by the third day of treatment.
Probiotics aren’t a replacement for OTC medicine when you need fast relief, but taking them alongside loperamide or bismuth subsalicylate is safe for most people and may help you recover faster.
When Antibiotics Are Needed
Most diarrhea is caused by viruses and resolves on its own. Antibiotics don’t help in those cases and can actually make things worse by disrupting the protective bacteria in your gut. Prescription antibiotics are reserved for bacterial diarrhea that’s moderate to severe, particularly traveler’s diarrhea that disrupts your ability to function or comes with fever or bloody stool.
Azithromycin is the preferred prescription choice for severe or bloody diarrhea and for travel in regions like Southeast Asia where antibiotic-resistant bacteria are common. Rifaximin is another option but only works against certain non-invasive strains of E. coli, so it’s not appropriate if a more aggressive bacterial infection is suspected. In either case, antibiotics typically shorten symptoms by one to two days compared to letting the illness run its course. These are decisions your doctor makes based on the severity and likely cause.
Who Should Avoid Anti-Diarrheal Medicine
Loperamide is not usually recommended during pregnancy because there isn’t enough safety data. If you’re pregnant and dealing with persistent diarrhea, talk to your doctor about what’s appropriate for your stage of pregnancy. Breastfeeding is a different story: only tiny amounts of loperamide pass into breast milk, and it’s generally considered safe.
You should also skip loperamide if your diarrhea includes a high fever (above 102°F) or bloody stools. In those situations, slowing down your gut can trap the infection inside rather than letting your body flush it out. Bismuth subsalicylate carries the same caution for bloody or febrile diarrhea, along with the aspirin-related restriction for anyone under 16.
Signs That Diarrhea Needs Medical Attention
In adults, diarrhea that doesn’t improve after two days, a fever over 102°F, black or bloody stools, or signs of dehydration (severe weakness, very dark urine, little to no urination) all warrant a call to your doctor. For children, the timeline is shorter: seek help if diarrhea hasn’t improved within 24 hours. Watch for no wet diaper in three or more hours, a dry mouth or tongue, crying without tears, unusual sleepiness, or skin that stays tented when you gently pinch it. These are signs of dehydration that can escalate quickly in small children.