The standard Prilosec (omeprazole) dose is 20 mg once daily, and for over-the-counter use, you should not take it for more than 14 days in a row. That 14-day course can be repeated every four months if symptoms return, meaning up to three courses per year. But the full picture depends on whether you’re using the OTC version for occasional heartburn or taking a prescription dose for a more serious condition.
OTC Prilosec: The 14-Day Rule
Over-the-counter Prilosec OTC comes in 20 mg delayed-release tablets. The label directs you to take one tablet per day for 14 consecutive days, not longer. This isn’t an “as needed” medication like antacids. It works by gradually reducing the amount of acid your stomach produces, and it needs all 14 days to do its job properly.
After finishing a 14-day course, you’re meant to wait at least four months before starting another one. If your heartburn keeps coming back and you find yourself reaching for Prilosec more than three times a year, that’s a signal something else may be going on that deserves a closer look.
Prescription Doses for Specific Conditions
When prescribed by a doctor, the dose is still typically 20 mg once daily, but the duration changes based on the condition being treated. For general acid reflux without esophageal damage, the standard course is up to 4 weeks. If you have erosive esophagitis, where stomach acid has actually damaged the lining of your esophagus, the course extends to 4 to 8 weeks at the same 20 mg dose.
For active duodenal ulcers, most people heal within four weeks on 20 mg daily, though some need an additional four weeks. People who have healed from erosive esophagitis may also stay on a maintenance dose of 20 mg daily to prevent it from returning.
The Highest Doses Used in Medicine
For rare conditions where the stomach massively overproduces acid, like Zollinger-Ellison syndrome, doses go far higher. The FDA-approved label lists a starting dose of 60 mg once daily for these patients, with adjustments based on individual need. In extreme cases, doses up to 120 mg three times daily (360 mg total) have been administered. Any daily dose above 80 mg is split into multiple doses throughout the day. These are medically supervised situations and not something to replicate on your own.
When Prilosec Starts Working
A single 20 mg dose reduces stomach acid output by about 33% within the first one to four hours. But you won’t feel the full benefit right away. With daily dosing, maximum acid suppression builds over the first four days. This is why Prilosec isn’t designed for instant heartburn relief. If you need something that works within minutes, an antacid is a better short-term option while the omeprazole ramps up.
Take the capsule before a meal, preferably in the morning. The drug works best when your stomach’s acid-producing pumps are active, which happens when you eat. Taking it on an empty stomach right before breakfast gives it the best chance to do its job.
Risks of Taking Too Much or Too Long
The bigger concern with Prilosec isn’t a single large dose. It’s the habit of taking it daily for months or years without medical guidance. Long-term use interferes with how your body absorbs calcium and magnesium. Over time, this can weaken bones: people on prolonged courses have a 35% higher risk of fractures compared to non-users, and the risk climbs further with higher doses.
Low magnesium from extended use can cause muscle spasms, irregular heartbeat, and in severe cases, seizures. These complications tend to emerge after months of continuous use, which is exactly why the OTC version caps you at 14 days. Long-term users also face a roughly threefold increase in the risk of a serious gut infection called C. difficile, and a somewhat higher risk of pneumonia. Stomach acid is part of your body’s defense system, and suppressing it indefinitely has consequences.
Signs You’ve Taken Too Much
An actual overdose of omeprazole can cause confusion, drowsiness, blurred vision, rapid or pounding heartbeat, nausea, vomiting, sweating, flushing, headache, and dry mouth. If you or someone else has taken a large amount, contact Poison Control at 1-800-222-1222. If there’s a seizure, loss of consciousness, or difficulty breathing, call 911 immediately.
The Practical Takeaway
For most people, 20 mg once daily is both the standard and the maximum appropriate dose. The key variable isn’t milligrams per day but how many days you take it. Stick to 14 days for OTC use, and if you need it longer or more frequently, that’s a conversation worth having with a provider who can check whether a higher dose, a longer course, or a different approach makes more sense for your situation.