Hello, I'm a healthcare professional with a background in pharmacology. When it comes to the onset of action for omeprazole, it's important to understand that this medication is a proton pump inhibitor (PPI) used to reduce the production of stomach acid. Omeprazole typically begins to work within one to several days of starting the medication. However, the full effect on reducing stomach acid may take up to a week or more to become noticeable. It's crucial to follow the prescribed dosage and instructions for the best results. read more >>

Prilosec OTC starts to work on the very first day of treatment, but may take 1 to 4 days for full effect (although some people get complete relief within 24 hours). Even though you may feel heartburn relief in the first few days, make sure to take the entire 14 days of dosing to treat your frequent heartburn.read more >>