Loperamide: what it treats, how to take it, side effects
Last updated September 3, 2026.
Loperamide is an antidiarrheal that slows the gut down so your body can absorb fluid again. You may know it as Imodium A-D. It controls the symptoms of diarrhea, including travelers' diarrhea - and there are specific kinds of diarrhea it must never be used for.
What does it treat?
The Imodium label says it plainly: controls symptoms of diarrhea, including travelers' diarrhea. MedlinePlus distinguishes over-the-counter use - acute diarrhea, taken after each loose stool - from prescription use, where it is sometimes taken on a schedule for chronic diarrhea under a doctor's care.
How do you take it?
For adults and children 12 and over, the label's OTC schedule is 2 caplets (2 mg each) after the first loose stool, then 1 caplet after each subsequent loose stool, and no more than 4 caplets in 24 hours. Children 6 to 11 get weight- or age-matched smaller doses; under 2, never. Measure the liquid with its dosing cup, not a kitchen spoon. Drink plenty of water or clear fluids throughout - replacing what the diarrhea takes out matters more than stopping it. Two stop rules from MedlinePlus: if your symptoms get worse or the diarrhea lasts longer than 48 hours, stop and call your doctor. Missed scheduled dose: take it when remembered unless the next one is close; never double up.
Side effects to know
- Common: constipation and fatigue. The drug can also make you drowsy and dizzy - do not drive until you know how it affects you.
- Serious: rash, red, peeling, or blistering skin, hives, itching, wheezing, difficulty breathing, fever, stomach pain or swelling, and bloody stools all mean calling your doctor immediately or getting emergency care. Overdose symptoms - nausea, inability to urinate, fainting, a fast, pounding, or irregular heartbeat, unresponsiveness - are 911-level.
Who should not take it?
The label's hard rule: do not use it if you have bloody or black stool, or if you have ever had an allergic reaction to loperamide. MedlinePlus expands the no-go list - tell your doctor first if you have ulcerative colitis or bacterial colitis, a fever, blood or mucus in the stool, black stools, or stomach pain without diarrhea, because your doctor will probably tell you not to take it. Slowing the gut down in an invasive infection traps the problem inside. Also flag AIDS and liver disease. If you are pregnant, planning pregnancy, or breastfeeding, talk to your doctor first.
When is it an emergency?
Call 911 for overdose signs - fainting, unresponsiveness, a fast, pounding, or irregular heartbeat, or inability to urinate. Bloody stools, stomach pain or swelling, fever, wheezing, or difficulty breathing mean immediate medical care. For a suspected overdose, Poison Control is 1-800-222-1222. Pymander's escalation routing is built and tested specifically for this class of decision; see the safety architecture working paper.
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Common questions
When should I NOT take Imodium?
The label is blunt: never with bloody or black stool, and never if you have had an allergic reaction to loperamide. MedlinePlus adds fever, blood or mucus in the stool, stomach pain without diarrhea, and ulcerative colitis or bacterial colitis as see-a-doctor-first situations. In those cases diarrhea is your body expelling something it needs to expel, and slowing the gut traps it.
How much Imodium can I take in a day?
Follow the label exactly: for adults and children 12 and over, 2 caplets after the first loose stool, 1 after each subsequent one, and no more than 4 caplets in 24 hours. MedlinePlus stresses staying under the 24-hour maximum - overdose symptoms include fainting, inability to urinate, and a fast or irregular heartbeat, which is 911 territory.
How long should diarrhea last before I call a doctor?
48 hours on loperamide. MedlinePlus says if your symptoms get worse or the diarrhea lasts longer than 48 hours, stop taking it and call your doctor. A fever, blood in the stool, or stomach swelling shortens that clock to now.
Can I take loperamide for travelers' diarrhea?
Yes - the Imodium label names travelers' diarrhea directly. The same stop rules apply abroad: bloody stool, fever, or worsening symptoms mean medical care, not more caplets. And fluids matter more than the pills - MedlinePlus says to drink plenty of water or clear fluids to replace what diarrhea takes out.
Can I give Imodium to my child?
Never under 2, and only per the package chart after that. The label gives weight- and age-matched doses for children 2 to 11 (with reduced caplet counts and daily maximums) and the adult schedule from 12 up. If you do not know the right dose for your child, ask the child's doctor.
Can I drink alcohol while taking loperamide?
Neither the FDA label nor MedlinePlus lists a specific alcohol interaction. But loperamide can make you drowsy and dizzy, and alcohol adds to both while also irritating an already irritated gut - skipping it until you are well is the sensible default, and your pharmacist can confirm.