For the original strength Pepto Bismol liquid, the standard adult dose is 30 mL (about two tablespoons) taken every 30 minutes as needed. You can also take 60 mL every hour. Either way, the hard limit is 8 doses, or 240 mL total, in a 24-hour period.
Dosing by Symptom
The dosing schedule depends on what you’re treating. For diarrhea or traveler’s diarrhea, you can take 30 mL every half hour or double up to 60 mL every hour. For general stomach upset, heartburn, indigestion, or nausea, the dose is 30 mL every half hour as needed.
In both cases, 240 mL (8 individual 30 mL doses) is the maximum you should take in 24 hours. If you’re measuring at home, 30 mL is equal to two tablespoons, so you’re looking at a cap of about 16 tablespoons across the full day. Most bottles come with a dosing cup to make measuring easier.
How Long You Can Keep Taking It
Pepto Bismol is meant for short-term use. If your symptoms haven’t improved after two days of regular dosing, that’s the point to stop and talk to a doctor rather than continuing at the maximum dose. Diarrhea that lasts beyond 48 hours, or stomach symptoms accompanied by fever, can signal something that an over-the-counter remedy won’t fix.
Black Tongue and Dark Stool
One side effect catches almost everyone off guard: your tongue and stool can turn dark gray or black while taking Pepto Bismol. This happens because bismuth, the active ingredient, reacts with trace amounts of sulfur in your saliva and digestive tract to form a harmless black compound. It’s not a sign of bleeding or anything dangerous. The discoloration typically clears up within several days after you stop taking the liquid.
Who Should Not Take It
Pepto Bismol contains salicylates, the same class of compound found in aspirin. That one detail creates a surprisingly long list of people who need to avoid it or check with a doctor first.
You should not take Pepto Bismol if you’ve ever had an allergic reaction to aspirin or any other pain reliever. The salicylate content also makes it a poor fit if you have a blood clotting disorder, gout, or diabetes, since it can interfere with how those conditions are managed.
Children under 12 should not take standard Pepto Bismol at all. Kids are more sensitive to salicylates, especially when they’re dehydrated from vomiting or diarrhea. More importantly, salicylates carry a risk of Reye’s syndrome, a rare but serious condition, in children and teenagers recovering from the flu or chickenpox. If a child in that age group has nausea or vomiting during one of those illnesses, it needs medical attention rather than an over-the-counter remedy. (Pepto Kids, a separate product, uses a different active ingredient.)
Interactions With Other Medications
Because of those salicylates, Pepto Bismol can interact with several common drug categories. Blood thinners are the most important one: taking salicylates on top of anticoagulant therapy increases the risk of bleeding. Oral diabetes medications and gout medications can also be affected.
If you’re taking tetracycline antibiotics like doxycycline or minocycline, leave at least a two-hour gap before taking Pepto Bismol, since bismuth can reduce how well the antibiotic is absorbed. And don’t combine it with aspirin or ibuprofen without checking with a pharmacist first, since stacking salicylates with other pain relievers raises the chance of side effects like stomach irritation.
Quick Reference
- Single dose: 30 mL (two tablespoons)
- Frequency: Every 30 minutes, or 60 mL every hour
- 24-hour max: 8 doses (240 mL)
- Duration: No more than 2 days without medical advice
- Age restriction: Adults and children 12 and older only