For an otherwise-healthy adult, sudden (acute) diarrhea is usually a self-limiting viral or foodborne illness that clears in a few days, so OTC self-care is a reasonable first move — but the honest framing matters: the thing that actually harms people is fluid and electrolyte loss (dehydration), not the loose stools. That makes rehydration, not an anti-diarrhea pill, the genuine first-line treatment (NIDDK: "Replacing lost fluids and electrolytes is the most important treatment for food poisoning"). Loperamide and bismuth subsalicylate control symptoms; they do not cure an infection and can worsen illness in the wrong setting. See a clinician instead of self-treating if there is blood in the stool, a high fever, or diarrhea that began during or soon after antibiotics — CDC states antidiarrheals "should be avoided if there is high fever or blood in the stools because they may make the illness worse."
Replaces the water, glucose, and electrolytes (sodium, potassium) lost in loose stools. It does not stop diarrhea — it keeps you safe from dehydration while the illness runs its course, which is the actual danger.
This is the guideline-endorsed first-line treatment. NIDDK: replacing lost fluids and electrolytes is "the most important treatment for food poisoning," and ORS is specifically advised for older adults, weakened immune systems, and severe diarrhea/dehydration. CDC clinician brief: for severe diarrhea, use ORS such as Ceralyte, Pedialyte or Oralyte to prevent dehydration.
Caution: CDC notes sports drinks such as Gatorade "do not replace the losses correctly and should not be used for the treatment of diarrheal illness" (though NIDDK lists diluted juice/sports drinks/broths as acceptable for most healthy adults with mild losses — proper ORS matters most for the very young, older adults, weakened immune systems, or heavy losses). Infants should keep getting breast milk or formula; ask a doctor before giving ORS to an infant. Being unable to keep any fluids down is a reason to seek care, not to keep trying at home.
Slows bowel movement so stools are less frequent and firmer. It reduces the number of loose stools in short-term, uncomplicated diarrhea but is symptom control only — it does not kill the cause of the diarrhea.
FDA-approved OTC use. MedlinePlus: OTC loperamide "is used to control acute diarrhea (loose stools that come on suddenly and usually lasts less than 2 weeks), including travelers' diarrhea." FDA states it "is a safe drug when used as directed."
Caution: US OTC maximum is 8 mg/day (follow the Drug Facts label); do not use OTC for more than 48 hours without medical advice (MedlinePlus/NHS). Do NOT use with fever, or blood, mucus, or black stools — MedlinePlus directs that a doctor will probably tell you not to take it in those cases; do not use for diarrhea starting during/after antibiotics (possible C. diff). Never exceed the label dose: FDA warns taking more than directed "can cause severe heart rhythm problems or death" (deaths have occurred with large overdoses/misuse, not approved doses). Not for children under 12 without a doctor, never under age 2. Ask a pharmacist first if you take heart-rhythm drugs (e.g. amiodarone, sotalol, quinidine) or have a QT/arrhythmia problem.
An antidiarrheal and upset-stomach remedy that can modestly shorten and ease simple diarrhea and also settles nausea/indigestion. Helpful for symptoms, not a cure for an infection.
CDC clinician brief: preparations of bismuth subsalicylate "can reduce the duration and severity of simple diarrhea." MedlinePlus: used "to treat diarrhea, heartburn, and upset stomach in adults and children 12 years of age and older." Stop and call a doctor if diarrhea lasts more than 2 days.
Caution: Contains a salicylate (aspirin-family): avoid with aspirin/salicylate allergy, and check with a pharmacist if you take warfarin, daily aspirin, or diabetes/gout/arthritis medicines. Do NOT use with an ulcer, a bleeding problem, or bloody/black stool; ask a doctor first with fever or mucus in the stool. Reye's syndrome risk — do not give to children/teens who have or are recovering from chickenpox or flu-like symptoms. It can harmlessly darken the tongue and/or stool (distinct from true black/tarry bleeding — if unsure, get checked). Ringing in the ears means stop and call a clinician. Separate tetracycline antibiotics by at least 1 hour before or 3 hours after.
For a healthy adult with short-lived, uncomplicated diarrhea and no warning signs, the smartest OTC plan is to rehydrate first — an oral rehydration solution is the real first-line treatment, not a sports drink — and optionally add loperamide or bismuth subsalicylate for symptom relief per the label, for no more than about 2 days. Do not use loperamide or bismuth if there is blood in the stool, a high fever, or diarrhea that began during or after antibiotics, and never exceed the loperamide label dose. If red flags appear — blood, high fever, dehydration, severe belly pain, symptoms past a couple of days, or a vulnerable patient — stop self-treating and get a clinician involved.
General information, not medical advice, and not a substitute for your clinician or pharmacist. Follow the label on any OTC product, mind interactions with your other medicines, and seek care for any red-flag symptom.