Acid reflux is one of the most common digestive complaints in the UK. For many people, it's an occasional nuisance. But when symptoms become frequent or persistent, a proton pump inhibitor like omeprazole is often the treatment that brings lasting relief.
It's one of the most widely used acid-reducing medicines in the country. You can buy some types from pharmacies, and others are available on prescription.1
This guide explains how omeprazole works for acid reflux, how long it takes to work, and when and how to take it. It also covers side effects, longer-term use, alternatives worth knowing about, and the symptoms that mean you should speak to a pharmacist or GP rather than treat yourself.
Omeprazole isn't instant relief. During a treatment course, take it every day as directed, not just when symptoms flare.
What is acid reflux, and when is omeprazole used?
Acid reflux happens when acid from your stomach travels back up into your oesophagus, the tube that connects your throat to your stomach.
The most familiar symptom is heartburn, a burning feeling in your chest, often after eating or when you lie down. You might also notice a sour taste, a feeling of food coming back up, or a cough that won't go away.
When reflux happens regularly over a longer period, it's called gastro-oesophageal reflux disease, or GORD.
Omeprazole is used for frequent heartburn and for GORD, including healing inflammation of the oesophagus caused by acid. It's also used for stomach and duodenal ulcers, and alongside antibiotics to treat Helicobacter pylori infection.1,2
Occasional, mild heartburn? An antacid or alginate from a pharmacy is often enough, rather than omeprazole.3
How does omeprazole work?
Omeprazole belongs to a group of medicines called proton pump inhibitors (PPIs). Your stomach lining contains cells with tiny "pumps", known as proton pumps, that release the acid your stomach uses to digest food. Omeprazole blocks these pumps, which reduces the amount of acid your stomach makes.1
Lowering stomach acid does two things. It eases the symptoms acid causes, such as heartburn and a sour taste. And it gives an irritated or inflamed oesophagus the chance to heal.2
Omeprazole doesn't neutralise acid that's already there, the way an antacid does. That's why it isn't designed for instant relief. Instead, it reduces how much acid is made in the first place.
How long does omeprazole take to work?
Omeprazole doesn't work straight away. You may need to take it for 2 to 3 days in a row before your symptoms improve. Most people taking a pharmacy course get complete relief from heartburn within 7 days.4 That gradual start is normal, and it isn't a sign the medicine isn't working.
Because the effect builds gradually, take it every day during a treatment course, as directed. Once a prescribed course has worked, some people are later advised to take it only when they need it. If that's you, follow your prescriber's plan.3
Bought omeprazole from a pharmacy, and your symptoms haven't improved within two weeks, or they've got worse? Speak to a pharmacist or GP rather than carrying on by yourself.1
When and how to take omeprazole
Omeprazole is usually taken once a day, in the morning. You can take it with or without food.1 Try to take it at the same time each morning, and swallow capsules and tablets whole with water. Do not chew or crush them.1,4
It commonly comes in 10mg, 20mg and 40mg strengths. 20mg is the usual dose for adults with reflux, while 40mg may be prescribed to heal more severe inflammation of the oesophagus.2
Omeprazole you buy from a pharmacy is for adults aged 18 and over, and it's meant for short-term use.1 A prescription allows a longer, supervised course where it's needed. Always follow the dose on the label, or the advice from your prescriber.
Taking other medicines? Check with a pharmacist before you start omeprazole. It must not be taken with nelfinavir, an HIV medicine. And it should not be taken with the blood thinner clopidogrel unless your doctor has agreed a suitable treatment plan.4 Do not stop any prescribed medicine yourself.
Same time, every morning. A steady daily routine matters more than whether you take it with breakfast.
Omeprazole side effects
Most people get on well with omeprazole, and many have no side effects at all. Common side effects (affecting up to 1 in 10 people) include:1,4
- Headache
- Diarrhoea or constipation
- Stomach pain or wind
- Feeling or being sick
Speak to a pharmacist or doctor if any side effects bother you or don't go away.1
Serious side effects are rare, but they're more likely if you take omeprazole for a long time, such as a year or more.1
Taking a PPI for a long time can lower the level of magnesium in your blood, which the MHRA has highlighted as a recognised effect.5 Long-term use has also been linked to low vitamin B12 levels and weakened bones that break more easily.1
If you get symptoms that worry you, such as muscle twitching, ongoing tiredness or a rash, speak to your GP or pharmacist.1,4
How long can you take omeprazole?
That depends on why you're taking it. Omeprazole bought without a prescription is meant for short-term use only, for no more than 14 days. If your symptoms carry on beyond that, see a GP so the cause can be properly looked into.1,4
When it's prescribed, omeprazole is often given as a four or eight-week course for GORD, after which your treatment is reviewed.3 If symptoms come back, the guidance is to use the lowest dose that keeps them under control, and some people only take it when they need it.3
If you get omeprazole 20mg through Pharmica, it's usually taken for 14 days at first. Some people need it for longer, up to a maximum of 28 days. If your symptoms carry on beyond 28 days, stop taking it and contact a pharmacist or GP.
If you take omeprazole long term, your treatment should be reviewed regularly.4
Taken it for a long time and want to stop? Talk to your prescriber first. They may suggest stepping down to a lower dose, or taking it only when needed.3
Do not keep taking pharmacy omeprazole beyond 14 days without seeing a GP.
Are there alternatives to omeprazole?
Omeprazole is one of several options for managing acid-related symptoms:
- Antacids and alginates - these work on acid that's already there, giving fast but short-lived relief. They're well suited to occasional heartburn, taken as needed.3
- H2 blockers - medicines such as famotidine reduce acid production in a different way to PPIs, and can be an option if a PPI isn't suitable.1,3
- Other PPIs - medicines such as lansoprazole and pantoprazole work in the same way as omeprazole, and may be tried if one PPI doesn't agree with you.3 Omeprazole is also sold over the counter as Pyrocalm.
- Lifestyle changes - these can make a real difference alongside treatment. Healthy eating, losing weight if you need to and stopping smoking can all help.3
You can find the full range of treatments on our acid reflux page, including omeprazole.
When to seek advice
Omeprazole is suitable for managing many cases of reflux, but some symptoms need to be checked by a healthcare professional first. Omeprazole can also hide the symptoms of some serious conditions.1 Speak to a GP, or seek urgent advice, if you:
- Have difficulty or pain when swallowing
- Are losing weight without trying to
- Keep being sick
- Vomit blood, or pass black or tarry stools (seek urgent medical attention)
- Keep getting symptoms despite a course of treatment, or need treatment for 4 weeks or more
- Are over 55 with new or recently changed symptoms (if you want Pharmica treatment, tell us if you are over 50 with new or changed reflux or indigestion symptoms, as our consultation asks about this. Alarm symptoms need prompt assessment at any age)
These can sometimes point to a condition that needs investigation rather than self-treatment.4
Vomiting blood, or black, tarry poo? That needs urgent medical attention. Go to A&E or call 999.
Chest pain isn't always reflux. A heart attack can sometimes feel like indigestion. Call 999 if you have tight or squeezing chest pain, pain that spreads to your arms, neck or jaw, or severe difficulty breathing.6 Do not assume it's reflux, and do not wait for omeprazole to work.
Frequently asked questions
How long does omeprazole take to work?
Omeprazole isn't a fast-acting medicine. Most people notice their symptoms easing within one to four days, and it can take a few days of taking it regularly to feel the full benefit. If you're using omeprazole bought from a pharmacy and there's no improvement after two weeks, speak to a pharmacist or GP.
When is the best time to take omeprazole?
Omeprazole is usually taken once a day in the morning, around 30 to 60 minutes before breakfast, as it works best when taken before food. Swallow the capsule or tablet whole with a drink of water rather than chewing it.
Can you take omeprazole long term?
It depends on why you're taking it. Omeprazole bought without a prescription is meant for short-term use only, usually no more than 14 days. When prescribed, it's often given as a course of a few weeks and then reviewed, and anyone using it long term should have their treatment checked regularly, as extended use is linked to lower magnesium and vitamin B12 levels and a small increase in fracture risk.
Can you take antacids with omeprazole?
Antacids work differently to omeprazole and act much faster, so some people use one for occasional breakthrough symptoms while omeprazole builds up its effect. If you plan to use both regularly, check with a pharmacist about how best to space them.
Can you drink alcohol while taking omeprazole?
Alcohol doesn't directly interact with omeprazole, but it can irritate the stomach and make heartburn and reflux worse. Cutting back may help your symptoms settle more quickly.
Is omeprazole safe to take during pregnancy?
Omeprazole is generally considered suitable during pregnancy when it's needed, but you should always speak to your GP or pharmacist before starting it so they can advise on the most appropriate option for you.
What is the difference between omeprazole and lansoprazole?
Both are proton pump inhibitors that reduce stomach acid in the same way, and they're similarly effective for reflux and heartburn. If one doesn't suit you, a prescriber may suggest trying the other. Pharmica's prescribers can help you work out which suits you better.
What should I do if omeprazole isn't working?
If your symptoms haven't improved after a two-week over-the-counter course, or they return once you stop, see a GP rather than continuing to self-treat. They can check the cause, review the dose, and rule out anything that needs further investigation. Do not ignore symptoms such as difficulty swallowing, unintended weight loss, or vomiting blood, which need prompt medical attention. And if you have tight or squeezing chest pain, or pain spreading to your arms, neck or jaw, call 999. Do not assume it's reflux.
References
- NHS. Omeprazole. NHS website; 2025. nhs.uk
- Neon Healthcare Ltd. Losec Capsules 20mg: Summary of Product Characteristics. Electronic Medicines Compendium; 2026. medicines.org.uk/emc
- National Institute for Health and Care Excellence. Gastro-oesophageal reflux disease and dyspepsia in adults: investigation and management (CG184). NICE; 2019. nice.org.uk
- Dexcel Pharma Ltd. Pyrocalm Control 20mg Gastro-Resistant Tablets: Summary of Product Characteristics. Electronic Medicines Compendium; 2025. medicines.org.uk/emc
- Medicines and Healthcare products Regulatory Agency. Proton pump inhibitors in long-term use: reports of hypomagnesaemia. GOV.UK; 2012. gov.uk
- NHS. Heart attack. NHS website; 2026. nhs.uk
This article is intended for informational purposes only and does not replace professional medical advice. Always read the patient information leaflet supplied with your medication and speak to a healthcare professional if you have specific concerns.