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) that is commonly used to reduce the production of stomach acid. Omeprazole typically starts to work within one to four days of daily dosing. However, the full effect of reducing stomach acid may not be noticeable for two to four weeks, as it can take some time for the stomach lining to heal. It's crucial to take the medication as prescribed by your healthcare provider and to follow the entire course of treatment. 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 >>