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Omeprazole Capsules (10mg & 20mg)

Omeprazole Capsules (10mg & 20mg)

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What Are Omeprazole Capsules UK and How Do They Help?

 

If you've ever felt that burning sensation creeping up your chest after a meal, you'll know how disruptive acid reflux can be. Omeprazole capsules UK are gastro-resistant capsules used to reduce the amount of acid your stomach produces, providing effective relief from heartburn, acid reflux, and indigestion. Available in 10mg and 20mg strengths, they belong to a class of medicines called proton pump inhibitors (PPIs) — one of the most widely used treatments for acid-related conditions in the UK. You can explore our full range of treatments in our indigestion collection.

Omeprazole is available over the counter (OTC) for adults aged 18 and over for short-term relief of heartburn symptoms. It is also used under medical supervision for longer-term conditions such as gastro-oesophageal reflux disease (GORD), gastric ulcers, and Helicobacter pylori eradication. At Cured Pharmacy, our omeprazole capsules are dispensed by GPhC-registered pharmacists, so you can order with confidence.

 

How Do Omeprazole Capsules Work to Reduce Stomach Acid?

 

Omeprazole works by targeting the root cause of excess stomach acid rather than simply neutralising it. Here's how the mechanism unfolds:

  • Omeprazole is absorbed in the small intestine and travels to the acid-secreting parietal cells in the stomach lining.
  • It irreversibly inhibits the hydrogen-potassium ATPase enzyme — commonly known as the "proton pump" — which is responsible for pumping acid into the stomach.
  • By blocking this pump, omeprazole significantly reduces the volume and concentration of gastric acid produced.
  • The effect builds over several days of consistent use, with maximum acid suppression typically achieved after 3–4 days of daily dosing.

Because the capsules are gastro-resistant, they pass through the stomach intact and dissolve in the small intestine. This protects the active ingredient from being broken down by stomach acid before it can be absorbed — which is why you should swallow the capsules whole and not crush or chew them.

 

Who Is Omeprazole Suitable For and What Conditions Does It Treat?

 

Omeprazole is suitable for a wide range of adults experiencing acid-related symptoms. It is used both as a short-term OTC remedy and as a longer-term prescription treatment. You might be a good candidate if you experience any of the following:

  • Frequent heartburn or acid reflux (occurring two or more days per week)
  • Indigestion that hasn't responded to antacids alone
  • Gastro-oesophageal reflux disease (GORD)
  • Gastric or duodenal ulcers, including those caused by NSAID use
  • Zollinger-Ellison syndrome (a rare condition causing excessive acid production)
  • As part of a combination therapy to eradicate Helicobacter pylori infection

It is not suitable for children under 18 for OTC use, and people with certain medical conditions or taking specific medicines should seek advice before starting omeprazole. If you regularly take pain relief medicines such as NSAIDs, you may be at increased risk of stomach ulcers — omeprazole is often prescribed alongside these to protect the stomach lining. Browse our pain relief collection if you're managing ongoing pain alongside acid symptoms.

 

How Does Omeprazole Compare to Other Acid Reflux Treatments?

 

Feature Omeprazole (PPI) Ranitidine / H2 Blocker (e.g. famotidine)
Mechanism Blocks proton pump (acid production) Blocks histamine H2 receptors (reduces acid)
Onset of action 1–4 days for full effect Within 1–3 hours
Duration of acid suppression Up to 24 hours per dose 6–12 hours per dose
Best suited for Frequent or persistent acid reflux, GORD, ulcers Occasional or mild heartburn

 

Is Omeprazole Safe to Store and Use Long Term?

 

For OTC use, omeprazole capsules UK should be stored below 25°C in a dry place, away from direct sunlight and out of reach of children. Do not use after the expiry date printed on the packaging. The capsules should be kept in their original blister pack until you are ready to take them.

Long-term use of omeprazole (beyond 14 days OTC, or as directed by your GP for prescription use) may be associated with certain risks, including reduced magnesium levels, vitamin B12 deficiency, and a small increased risk of bone fractures with prolonged high-dose use. If you have been taking omeprazole for an extended period, your doctor may recommend periodic blood tests to monitor for these effects. Always follow the guidance of your prescriber or pharmacist.

This product is a medicine. Speak to your doctor or pharmacist before using if you have an underlying medical condition or are taking other medicines.

Omeprazole Capsules (10mg & 20mg) specifications
Treatment category Acid-related gastrointestinal conditions
Mechanism of action Proton pump inhibitor (PPI) — irreversibly inhibits H+/K+ ATPase enzyme
Effective for Heartburn, acid reflux, GORD, gastric ulcers, NSAID-induced ulcer prevention
Suitable for Adults aged 18 and over
Active ingredient Omeprazole
Pack sizes 7, 14, or 28 capsules (varies by pack)
Strengths 10mg, 20mg
UK classification Pharmacy (P) medicine — available OTC
Drug class Proton pump inhibitor (PPI)
Preparation Gastro-resistant capsules
Route of administration Oral

Specifications of Omeprazole Capsules (10mg & 20mg)

 

What Is Omeprazole and What Is It Used For?

 

Omeprazole is a proton pump inhibitor (PPI) used to treat conditions caused by excess stomach acid. It is one of the most commonly prescribed and purchased medicines in the UK. Over the counter, it is used by adults to relieve heartburn and acid indigestion. On prescription, it treats gastro-oesophageal reflux disease (GORD), gastric and duodenal ulcers, and is used as part of combination therapy to eradicate Helicobacter pylori — a bacterial infection that can cause stomach ulcers.

Omeprazole reduces the amount of acid your stomach produces, which in turn allows the oesophagus and stomach lining to heal and symptoms to subside. It does not work immediately for all symptoms — for heartburn, some people notice improvement within 24 hours, but full benefit may take 3–4 days of consistent use.

 

What Do You Need to Know Before Using Omeprazole?

 

Before taking omeprazole, it's important to check whether it is appropriate for you. Do not take omeprazole if any of the following apply:

  • You are allergic to omeprazole or any other proton pump inhibitor (such as lansoprazole, pantoprazole, or esomeprazole)
  • You are under 18 years of age (for OTC use)
  • You have difficulty swallowing or unexplained weight loss — these symptoms require medical investigation before starting treatment
  • You have been told you have a low magnesium level in your blood
  • You are pregnant or breastfeeding — seek medical advice first

The following medicines may interact with omeprazole. Tell your pharmacist or doctor if you are taking:

  • Clopidogrel (a blood-thinning medicine) — omeprazole may reduce its effectiveness
  • Methotrexate — omeprazole may increase methotrexate levels in the blood
  • HIV medicines such as atazanavir or nelfinavir — omeprazole may reduce their absorption
  • Warfarin or other anticoagulants — monitoring may be required
  • Digoxin, ketoconazole, or itraconazole — absorption may be affected

 

How Should You Use Omeprazole Capsules Correctly?

 

Always use omeprazole exactly as directed on the packaging or by your pharmacist or GP. Follow these steps for correct use:

  1. Take omeprazole 30–60 minutes before a meal — ideally breakfast.
  2. Swallow the capsule whole with a glass of water. Do not crush, chew, or open the capsule.
  3. If you have difficulty swallowing, you may open the capsule and mix the granules into a small amount of slightly acidic liquid (such as fruit juice or yoghurt) — swallow immediately without chewing.
  4. Take one capsule once daily unless your doctor has advised otherwise.
  5. For OTC heartburn relief, do not take for more than 14 days without speaking to a doctor.
Indication Age Group Dose Duration
Heartburn / acid reflux (OTC) Adults 18+ 20mg once daily Up to 14 days
GORD (prescription) Adults 20mg once daily 4–8 weeks (as directed)
Gastric ulcer (prescription) Adults 20mg once daily 4–8 weeks (as directed)
NSAID-induced ulcer prevention (prescription) Adults 20mg once daily As directed by GP
Maintenance / low-dose (prescription) Adults 10mg once daily As directed by GP

If you are managing other digestive symptoms alongside acid reflux — such as bloating or cramping — you may find it helpful to browse our IBS and cramps collection for additional support options.

 

What Are the Possible Side Effects of Omeprazole?

 

Like all medicines, omeprazole can cause side effects, although not everyone experiences them. Most side effects are mild and short-lived.

Common side effects (may affect up to 1 in 10 people):

  • Headache
  • Diarrhoea
  • Nausea or vomiting
  • Stomach pain or discomfort
  • Flatulence (wind)
  • Constipation

Less common side effects (may affect up to 1 in 100 people):

  • Dizziness or sleep disturbances
  • Skin rash or itching
  • Swelling of the feet or ankles
  • Dry mouth
  • Low magnesium levels (with long-term use) — symptoms include muscle cramps, irregular heartbeat, or tremors

Rarely, omeprazole can cause serious allergic reactions (anaphylaxis), severe skin reactions, or liver problems. Stop taking omeprazole and seek immediate medical attention if you develop swelling of the face, lips, or throat, difficulty breathing, or a severe skin rash.

 

How Should You Store Omeprazole Capsules?

 

  • Store below 25°C in a dry place, away from direct sunlight and moisture.
  • Keep in the original blister packaging until ready to use.
  • Keep out of the sight and reach of children.
  • Do not use after the expiry date printed on the pack.
  • Do not dispose of medicines via wastewater or household waste — return unused capsules to your pharmacy for safe disposal.

If you're supporting your overall gut health alongside acid management, it's worth knowing that certain vitamins and minerals — particularly magnesium and vitamin B12 — may be affected by long-term PPI use. Our vitamins and supplements collection includes options that may help support nutritional balance during extended treatment.

Written and reviewed by our qualified team

Your safety and success are our highest priorities. Our medical team rigorously evaluates every product and piece of advice we provide, ensuring you receive only the most effective, science-backed solutions available.

Frequently Asked Questions

Where can I buy omeprazole capsules online in the UK?

You can buy omeprazole capsules online in the UK from Cured Pharmacy, a GPhC-registered online pharmacy. Both 10mg and 20mg strengths are available without a prescription for adults aged 18 and over, subject to a short suitability check. Simply add the product to your basket, complete the online consultation, and your order will be dispensed and dispatched by our qualified pharmacy team.

How does omeprazole work in the body?

Omeprazole works by irreversibly blocking the hydrogen-potassium ATPase enzyme — the so-called "proton pump" — found in the acid-secreting parietal cells of the stomach lining. By inhibiting this pump, omeprazole directly reduces the volume and concentration of gastric acid produced. The effect accumulates over several days, with maximum acid suppression typically reached after 3–4 days of daily use.

How do I take omeprazole capsules step by step?

Take one omeprazole capsule 30–60 minutes before your first meal of the day, swallowing it whole with a full glass of water — do not crush or chew it. If you struggle to swallow capsules, you can open the capsule and mix the granules into a small amount of slightly acidic liquid such as apple juice, then swallow immediately without chewing the granules. For OTC heartburn relief, take one 20mg capsule once daily for up to 14 days unless your GP has advised otherwise.

What is the best time of day to take omeprazole?

The best time to take omeprazole is in the morning, approximately 30–60 minutes before breakfast. Taking it before food ensures the medicine is properly absorbed and that the proton pumps are active and available to be blocked when you eat. If you are taking omeprazole twice daily on prescription, take the second dose before your evening meal.

What is the correct dose of omeprazole for heartburn?

For OTC heartburn relief in adults aged 18 and over, the standard dose is omeprazole 20mg once daily for up to 14 days. The 10mg strength is sometimes used as a lower maintenance dose under GP guidance. Do not exceed the recommended dose, and if your symptoms have not improved after 14 days, consult your GP rather than continuing to self-treat.

What are the most common side effects of omeprazole?

The most common side effects of omeprazole include headache, diarrhoea, nausea, stomach pain, flatulence, and constipation — these affect up to 1 in 10 people. Most side effects are mild and tend to resolve without any specific treatment as your body adjusts. If side effects are troublesome or persistent, speak to your pharmacist or GP, who may suggest an alternative acid-suppressing medicine.

How do I manage side effects of omeprazole?

For mild side effects such as headache or nausea, taking omeprazole with a small amount of food (rather than on an empty stomach) may help, though it is ideally taken before meals. Staying well hydrated and avoiding triggers such as fatty foods, caffeine, and alcohol can also reduce gastrointestinal discomfort. If you experience more serious side effects — such as muscle cramps, irregular heartbeat, or a severe skin reaction — stop taking omeprazole and seek medical advice promptly.

Who should not take omeprazole capsules?

Omeprazole is not suitable for people with a known allergy to omeprazole or other proton pump inhibitors such as lansoprazole, pantoprazole, or esomeprazole. It should not be used by anyone under 18 for OTC purposes, and caution is needed in people taking clopidogrel, methotrexate, or certain HIV antivirals. If you are pregnant, breastfeeding, or have liver disease, speak to your GP or pharmacist before taking omeprazole.

What happens if I miss a dose of omeprazole?

If you miss a dose of omeprazole, take it as soon as you remember — provided it is not nearly time for your next scheduled dose. If it is close to your next dose, simply skip the missed one and continue as normal. Never take two doses at the same time to compensate for a missed dose, as this will not improve your symptoms faster and may increase the risk of side effects.

Can I take omeprazole with other medicines?

Omeprazole can interact with several medicines, including clopidogrel (where it may reduce antiplatelet effectiveness), methotrexate, warfarin, and certain HIV antivirals such as atazanavir. It may also affect the absorption of medicines that depend on stomach acid, such as ketoconazole, itraconazole, and digoxin. Always tell your pharmacist or GP about all medicines, supplements, and herbal remedies you are taking before starting omeprazole.

How long can you take omeprazole for?

For OTC use, omeprazole should not be taken for more than 14 consecutive days without medical advice. For prescription use, your GP may recommend a longer course — typically 4–8 weeks for ulcer healing or ongoing maintenance therapy for GORD. Long-term use should be reviewed regularly by your doctor, as prolonged PPI use has been associated with low magnesium levels and reduced vitamin B12 absorption over time.

Is omeprazole 10mg or 20mg better for me?

The 20mg dose is the standard OTC dose for heartburn and acid reflux in adults, and is the strength most commonly recommended for short-term symptom relief. The 10mg dose is typically used as a lower maintenance dose under GP supervision once symptoms are controlled. If you are unsure which strength is right for you, speak to your pharmacist before purchasing.

What are the alternatives to omeprazole for acid reflux?

Alternatives to omeprazole include other proton pump inhibitors such as lansoprazole, pantoprazole, and esomeprazole, which work in a similar way. H2 receptor antagonists such as famotidine offer a faster onset of action but shorter duration of acid suppression, making them more suitable for occasional heartburn. Antacids such as calcium carbonate or sodium alginate provide rapid but short-lived relief and are best for mild, infrequent symptoms. You can explore related digestive health options in our indigestion collection.

Can omeprazole be taken during pregnancy or breastfeeding?

Omeprazole is not recommended for OTC use during pregnancy or breastfeeding without first consulting a GP or midwife. While omeprazole is sometimes prescribed during pregnancy when the benefits outweigh the risks, this decision should always be made under medical supervision. If you are pregnant and experiencing heartburn, your GP or midwife can advise on the safest treatment options for you and your baby.

What does the latest research say about long-term omeprazole use?

Research has highlighted that long-term PPI use — particularly at high doses — may be associated with a small increased risk of bone fractures, low magnesium (hypomagnesaemia), vitamin B12 deficiency, and Clostridioides difficile infection. The NHS and MHRA advise that PPIs should be used at the lowest effective dose for the shortest necessary duration. If you have been on omeprazole long term, your GP may periodically review your need for continued treatment and monitor relevant blood markers. For general wellbeing support during long-term treatment, our vitamins and supplements collection may be of interest.

How Should You Use Omeprazole Capsules?

Using omeprazole correctly makes a real difference to how well it works. The capsules are gastro-resistant, which means they are specially designed to pass through your stomach intact and dissolve in your small intestine — so it's important not to interfere with that process by crushing or chewing them. Follow these steps each time you take a dose:

What Is the Correct Dose of Omeprazole Capsules?

The dose of omeprazole depends on what you are treating and whether you are using it OTC or on prescription. Always follow the instructions on the packaging or as directed by your GP. The table below summarises the standard dosing guidance:

When Is the Best Time to Use Omeprazole Capsules?

Timing matters more than many people realise with omeprazole. The medicine works by blocking proton pumps that are only active when stimulated by food — so taking it before a meal ensures the pumps are ready to be inhibited when you eat. Morning is the ideal time for most people, as it aligns with the largest meal of the day and provides acid suppression throughout the period when symptoms are most likely to occur. If you are prescribed a twice-daily dose, take the second capsule before your evening meal rather than at bedtime.

How Long Can You Use Omeprazole Capsules For?

For OTC use, omeprazole should not be taken for more than 14 consecutive days without speaking to a doctor. If your symptoms return after completing a 14-day course, or if they have not improved, this is a sign that you need a medical review rather than another self-treatment course. For prescription use, your GP will advise on the appropriate duration — this may range from 4–8 weeks for ulcer healing to longer-term maintenance therapy for conditions such as GORD. Long-term use should always be reviewed periodically by your doctor to ensure it remains necessary and appropriate.

Do not exceed the recommended dose. If in doubt, speak to your pharmacist.

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Side Effects Of Omeprazole Capsules (10mg & 20mg)



Omeprazole is generally well tolerated, but some people may experience side effects.

Common (1 in 10 people):

  • Headache
  • Stomach pain or discomfort
  • Nausea
  • Diarrhoea or constipation
  • Bloating or gas
  • Dizziness

Uncommon (1 in 100 people):

  • Sleep disturbance
  • Dry mouth
  • Mood changes
  • Skin rash
  • Fatigue
  • Swelling of the ankles

Rare but Serious:

  • Severe allergic reactions
  • Persistent diarrhoea (possible infection)
  • Yellowing of the skin or eyes (liver issues)
  • Very low magnesium levels (causing muscle cramps or heart rhythm changes)
  • Vitamin B12 deficiency with long-term use
  • Increased fracture risk with prolonged high-dose use

Seek immediate medical help if serious side effects occur.

Patient Information Leaflet

Important - Before taking any medication, it is always important to read the Patient Information Leaflet (PIL)

Written and reviewed by our qualified team

GPhC Number: 2233073
Tarun Kumar

Reviewed by:

Tarun Kumar

Superintendent/ Clinical Lead

📖 Find out more about our team of medical content authors and how we ensure the accuracy of our content with our content guidelines.

Content last updated: 31 Mar 2025

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