How long does it take omeprazole to heal gastritis?
Ethan Hayes
Published Jan 11, 2026
Omeprazole starts to work within 2 to 3 days, but it may take up to 4 weeks for it to work fully. You'll usually take omeprazole once a day, in the morning. For Zollinger-Ellison syndrome, you can take it twice a day – in the morning and in the evening. Common side effects include headaches, diarrhoea and stomach pain.