Famotidine: what it treats, how to take it, side effects
Last updated September 3, 2026.
Famotidine is an acid reducer that tells your stomach to make less acid. You may know it as Pepcid. It belongs to the H2 blocker class, sold over the counter for heartburn and prescribed at higher doses for ulcers and reflux disease.
What does it treat?
Two worlds. Over the counter: preventing and treating heartburn, acid indigestion, and sour stomach caused by eating or drinking certain things. By prescription: stomach and intestinal ulcers, gastroesophageal reflux disease (GERD), and conditions where the stomach overproduces acid, like Zollinger-Ellison syndrome. Same drug, different jobs and doses.
How do you take it?
Over the counter, it works two ways: swallow 1 tablet with a full glass of water to relieve heartburn, or take it 15 to 60 minutes before a meal you expect to cause trouble to prevent it. Hard limits from MedlinePlus and the label: no more than 2 tablets in 24 hours, and do not take OTC famotidine for longer than 2 weeks - if heartburn outlasts that, stop and call your doctor. Prescription schedules run once daily at bedtime or two to four times a day. Shake the liquid 5 to 10 seconds, chew the chewables thoroughly, and swallow regular tablets whole with water. Missed prescription dose: take it when you remember unless the next one is close; never double up.
Side effects to know
- Common: headache, dizziness, constipation, and diarrhea.
- Serious: allergic reactions - hives, skin rash, itching, swelling of the face, throat, tongue, lips, eyes, hands, feet, ankles, or lower legs, hoarseness, and difficulty breathing or swallowing. Call your doctor immediately or get emergency care.
Who should not take it?
Anyone allergic to famotidine or other acid reducers like cimetidine, nizatidine, or ranitidine. The label's do-not-use list doubles as a when-heartburn-is-not-heartburn checklist: heartburn for over 3 months, heartburn with lightheadedness, sweating, or dizziness, chest pain or shoulder pain with shortness of breath or pain spreading to the arms, neck, or shoulders, frequent wheezing, unexplained weight loss, nausea or vomiting, or stomach pain - any of these means a doctor, not an acid reducer. Tell your doctor about kidney disease, trouble swallowing, and PKU (some chewables contain aspartame). Do not stack it with other heartburn medications without a pharmacist's say-so. Pregnant or breastfeeding: talk to your doctor first.
When is it an emergency?
Difficulty breathing or swallowing, or swelling of the face, throat, or tongue, is a 911 call - that is an allergic reaction. Chest pain with shortness of breath, sweating, or pain spreading to the arms, neck, or shoulders is never an antacid problem - treat it as an emergency first. For an overdose, call Poison Control at 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
How is famotidine different from omeprazole?
Different class, different clock. Famotidine is an H2 blocker - it reduces stomach acid and can be taken 15 to 60 minutes before a problem meal for prevention. Omeprazole is a proton pump inhibitor, a stronger shutoff taken daily over a course. For occasional heartburn, the H2 blocker is the usual first step; frequent heartburn past 2 weeks is a doctor conversation either way.
Why does the label say not to use it for more than 2 weeks?
Because long-running heartburn needs a diagnosis. MedlinePlus says if symptoms of heartburn, acid indigestion, or sour stomach last longer than 2 weeks, stop taking over-the-counter famotidine and call your doctor. The label adds that heartburn lasting over 3 months may signal a more serious condition. The 2-week cap keeps a treatable symptom from masking a real problem.
Can I take famotidine every day?
Within limits, yes - up to 2 tablets in 24 hours, for up to 2 weeks over the counter. Daily need past that window moves it into prescription territory, where your doctor sets the schedule (once at bedtime or two to four times a day) and the reason gets investigated.
Can I drink alcohol while taking famotidine?
Neither the FDA label nor MedlinePlus lists a specific alcohol interaction for famotidine. Alcohol is a classic heartburn trigger though - the label literally describes preventing heartburn brought on by eating or drinking certain things - so it works against the reason you are taking the pill.
Is famotidine the same as ranitidine (Zantac)?
Same class, different molecule. Both are H2 blockers, and MedlinePlus lists ranitidine alongside cimetidine and nizatidine as related acid reducers to mention for allergy purposes. Ranitidine products were withdrawn from the US market years ago; famotidine remains the standard H2 blocker on shelves.
Can I take famotidine while pregnant?
Talk to your doctor first. MedlinePlus says to tell your doctor if you are pregnant, planning pregnancy, or breastfeeding, and to call if you become pregnant while taking it. Heartburn is common in pregnancy, but the choice of treatment belongs to your clinician.