Proton pump inhibitorAcid reducer

Omeprazole

Capsule or tablet

Quick Summary

Omeprazole is a proton pump inhibitor (PPI). It reduces the amount of acid the stomach makes, which relieves heartburn and lets the food pipe and stomach lining heal.

Heartburn and acid reflux
Stomach and duodenal ulcers
H. pylori infection
Protecting the stomach

Medical Uses

Heartburn and acid reflux: Eases burning pain and acid coming back up (GORD).
Stomach and duodenal ulcers: Helps ulcers heal and prevents them coming back.
H. pylori infection: Used with antibiotics to clear this stomach bacterium.
Protecting the stomach: Sometimes given with anti-inflammatory painkillers to protect the stomach.

How it's taken

Omeprazole is usually taken once a day, before a meal, often in the morning. Swallow capsules whole. Your doctor decides the right dose for you and may change it over time.

For short-term heartburn it may be bought from a pharmacy; see a doctor if symptoms last more than a couple of weeks or keep coming back.

Your doctor decides the right dose for you. Follow their instructions and the label.

Common Side Effects

Headache

Usually mild.

Stomach upset

Feeling sick, diarrhoea, constipation, wind or tummy pain.

Long-term effects

Using it for many years may slightly increase the risk of low magnesium, low vitamin B12 and bone fractures.

Interactions

Clopidogrel

Omeprazole can make this blood thinner work less well; your doctor may choose a different acid reducer.

Some HIV medicines

Some can't be taken with omeprazole.

Methotrexate

High doses of methotrexate with omeprazole may need closer monitoring.

Critical Warnings

Warning signs of a serious problem

Black Box Warning: See a doctor urgently for difficulty swallowing, vomiting blood, black stools or unexplained weight loss.

Long-term use

Your doctor should review regularly whether you still need it.

Sources and further reading

Last updated 21 October 2026. For more detail, see these trusted health organisations.