For occasional heartburn, you can take one Pepcid (famotidine) tablet up to twice a day, with doses spaced about 12 hours apart. A single 20 mg dose suppresses stomach acid for 10 to 12 hours, so twice daily is enough to cover a full 24-hour period. The specifics change depending on whether you’re using the over-the-counter version for heartburn or a prescription dose for a more serious condition.
OTC Dosing for Heartburn
The standard over-the-counter Pepcid dose is 10 mg or 20 mg, taken once or twice daily. If you’re using it to prevent heartburn before a meal, take one tablet 15 to 60 minutes before eating. Relief typically starts within an hour, with peak effect hitting between one and three hours after you swallow the tablet.
For ongoing heartburn, you can take one dose in the morning and one at bedtime. OTC Pepcid packaging generally recommends no more than two tablets per day and advises limiting continuous use to about two weeks. If your symptoms persist beyond that, it’s worth getting evaluated for something more than occasional acid irritation.
Prescription Doses Are Higher
When prescribed for ulcers, the typical regimen is 20 mg twice daily (morning and bedtime) or 40 mg once at bedtime, continued for up to 8 weeks. For erosive esophagitis, a more severe form of acid damage, the same dosing applies but can extend up to 12 weeks.
For rare conditions that cause extreme acid overproduction, the starting dose jumps to 20 mg every 6 hours, four times a day. In those cases, the dose can be increased significantly under medical supervision. These are not situations where you’d be self-dosing from an OTC bottle.
How Long Each Dose Lasts
Pepcid works by blocking histamine receptors in the stomach lining, which reduces the amount of acid your stomach produces. One 20 mg or 40 mg dose keeps acid suppressed for roughly 10 to 12 hours. That’s why twice-daily dosing is the most common schedule: it covers both daytime and overnight acid production without gaps.
Compared to antacids like Tums, which neutralize acid already in your stomach and wear off in about an hour, Pepcid works upstream by preventing acid from being released in the first place. The tradeoff is that it takes longer to kick in (up to an hour) but lasts much longer.
Your Body Builds Tolerance Quickly
One thing most people don’t realize is that Pepcid starts losing effectiveness almost immediately with daily use. A measurable decline in acid suppression shows up by the second day. By day 3 of continuous use, efficacy drops by about 11%. By two weeks, the drug retains only about 72% to 87% of its original acid-blocking power.
What makes this more significant than it sounds: compared to how well the drug worked on day one, the actual reduction in acid suppression can approach 50% by day 15. After that point, the tolerance levels off and doesn’t get much worse, but it also doesn’t improve. Taking a higher dose won’t overcome this tolerance, either. The effect seems to involve more than just the receptors Pepcid targets.
This tolerance effect is one reason Pepcid works best for short-term or occasional use. If you find yourself needing daily acid suppression for months, a different class of medication (like a proton pump inhibitor) may be more appropriate for sustained relief.
Kidney Function Changes the Math
Famotidine is cleared through the kidneys, so reduced kidney function means the drug stays in your system longer and builds to higher levels. People with moderate kidney impairment typically need to cut the dose to about 25% of the standard amount. With severe impairment, the dose drops to roughly 10% of normal. If you have kidney disease, your dosing schedule will look very different from what’s on the OTC label.
Dosing for Children
Children’s doses are weight-based rather than fixed. For kids ages 1 through 16, the typical starting dose for acid reflux is 0.5 mg per kilogram of body weight, given twice daily. That can be increased up to 1 mg per kilogram twice daily, with a ceiling of 40 mg per dose. For infants under 3 months, the frequency drops to once daily. Children’s formulations come as an oral suspension, making it easier to measure precise doses.
Pregnancy Considerations
There isn’t enough human data to definitively confirm or rule out risks from famotidine during pregnancy. Animal studies haven’t shown clear harm, but animal results don’t always translate to humans. Pepcid is generally considered one of the better-studied options among acid reducers for pregnant women, but it’s a decision best made with your OB or midwife rather than on your own from the pharmacy shelf.