The standard adult dose of omeprazole is 20 mg once a day, and most people should not exceed 40 mg per day without medical supervision. The over-the-counter version is sold as a 20 mg tablet meant to be taken once daily for 14 days at a time, while prescription doses can go higher depending on the condition being treated.
Standard Doses for Common Conditions
For most adults dealing with acid reflux or heartburn, 20 mg once a day is the recommended dose. This applies to both the OTC product (sold as Prilosec OTC) and the standard prescription strength. If you have erosive damage to the esophagus from chronic reflux, the dose stays at 20 mg daily but treatment typically extends from 4 weeks to 8 weeks.
Gastric ulcers call for a higher dose. The FDA-approved regimen for active stomach ulcers is 40 mg once a day for 4 to 8 weeks. For treating an H. pylori infection, which is a common bacterial cause of ulcers, omeprazole is prescribed at 20 mg twice daily (totaling 40 mg per day) alongside antibiotics for about 14 days.
So for the vast majority of people, the daily ceiling is 40 mg, taken either as one 40 mg dose or two 20 mg doses.
When Higher Doses Are Prescribed
There is one condition where doses climb well beyond 40 mg. Zollinger-Ellison syndrome is a rare disorder where tumors cause the stomach to produce extreme amounts of acid. For these patients, the starting dose is 60 mg once a day, and doctors may increase it up to 360 mg per day (split into three doses of 120 mg). Any dose above 80 mg per day is given in divided doses rather than all at once. Some patients with this condition stay on high-dose omeprazole for five years or longer.
These doses are prescribed under close medical monitoring and don’t apply to typical acid reflux or ulcer treatment.
OTC Rules: The 14-Day Cycle
If you’re buying omeprazole over the counter, the FDA sets specific limits. You take one 20 mg tablet per day, every day, for 14 consecutive days. That’s one treatment course. You should not extend it beyond 14 days on your own or take more than one tablet per day.
The 14-day course can be repeated, but not immediately. If your symptoms return after finishing a course, the standard guidance is to wait at least four months before starting another 14-day round. If you find yourself needing it more frequently than that, you likely need a prescription-strength plan rather than self-treating with OTC tablets.
Timing and How to Take It
Omeprazole works best when you take it before a meal, ideally in the morning. If you’re on a twice-daily dose, take one in the morning and one in the evening, keeping the timing consistent from day to day. The capsules or tablets should be swallowed whole rather than crushed or chewed, since the delayed-release coating protects the medication from being broken down by stomach acid before it reaches the right part of your digestive system.
If you miss a dose, take it when you remember unless it’s nearly time for your next one. Don’t double up to compensate for a missed dose.
What Happens If You Take Too Much
Omeprazole has a relatively wide safety margin. Reported overdose cases are rare, and the symptoms observed have been mild: flushing, rapid heart rate, and headache. The drug’s behavior in the body doesn’t appear to change dramatically in overdose situations, meaning it’s processed and cleared at roughly the same rate.
That said, “not acutely dangerous” is different from “safe to take extra.” Taking more than your prescribed or recommended dose over time increases the risk of side effects that build gradually. Long-term use at higher-than-necessary doses has been linked to reduced absorption of magnesium and calcium, which can affect bone density over months or years. It can also lower vitamin B12 levels and increase susceptibility to certain gut infections, since stomach acid serves as a barrier against bacteria.
Quick Reference by Condition
- Heartburn or mild GERD (OTC): 20 mg once daily for 14 days
- GERD with esophageal damage (prescription): 20 mg once daily for 4 to 8 weeks
- Stomach ulcer: 40 mg once daily for 4 to 8 weeks
- H. pylori treatment: 20 mg twice daily (with antibiotics) for 14 days
- Zollinger-Ellison syndrome: 60 to 360 mg daily, divided into multiple doses
For most people, 20 mg once a day handles the job. If that’s not enough, 40 mg per day is the next step, but at that point you should be working with a prescriber rather than doubling your OTC dose on your own.