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About omeprazole - Brand names: Losec, Losec MUPS, Pyrocalm

Omeprazole reduces the amount of acid your stomach makes. It's widely used to treat indigestion and heartburn, and acid reflux. It's also taken to prevent and treat stomach ulcers.

Omeprazole is a type of medicine called a proton pump inhibitor (PPI). Proton pumps are enzymes in the lining of your stomach that help it make acid to digest food. Omeprazole prevents proton pumps working properly which reduces the amount of acid the stomach makes.

Sometimes, omeprazole is taken for a rare condition caused by a tumour in the pancreas or gut called Zollinger-Ellison syndrome.

Omeprazole comes as capsules, tablets and as a liquid that you swallow.

All types of omeprazole are available on prescription. You can buy 20mg tablets from pharmacies and supermarkets.

Key facts

  • 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. These tend to be mild and go away when you stop taking the medicine.
  • If you buy omeprazole from a pharmacy or supermarket to treat yourself, do not take it for longer than 2 weeks without checking with a doctor.
  • Alcohol can make your stomach produce more acid than normal. This irritates the stomach lining and can make your symptoms worse. It's best to avoid alcohol if possible while you're taking omeprazole.

Page last reviewed: 18 November 2021
Next review due: 18 November 2024