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Losec Capsules & Tablets (Omeprazole) 20mg

Losec Capsules & Tablets (Omeprazole) 20mg

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  • 5. Supports cardiovascular risk reduction
  • 6. Over 22 million patients treated with semaglutide-based therapies since 2018

  • ✔️ Reduces stomach acid production for up to 24 hours
  • ✔️ Relieves heartburn and acid reflux symptoms effectively
  • ✔️ Helps heal gastric and duodenal ulcers in adults
  • ✔️ Protects stomach lining when taking NSAID painkillers
  • ✔️ Gastro-resistant formula ensures targeted intestinal absorption

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What Is Omeprazole 20mg and How Does Losec Help?

 

If you've ever dealt with that burning sensation creeping up your chest after a meal, you'll know how disruptive acid reflux can be. Omeprazole 20mg, sold under the well-known brand name Losec, is a clinically established treatment for exactly this kind of discomfort. It belongs to a class of medicines called proton pump inhibitors (PPIs), and it works by reducing the amount of acid your stomach produces. Whether you're managing occasional heartburn or a diagnosed condition like gastro-oesophageal reflux disease (GORD), Losec is one of the most widely used options available in the UK. You can explore our full range of indigestion treatments if you'd like to compare your options.

Losec capsules and tablets both contain omeprazole 20mg as the active ingredient. The capsules are gastro-resistant, meaning they're designed to pass through the stomach intact and dissolve in the small intestine — this protects the medicine from being broken down by stomach acid before it can work. The tablets are also gastro-resistant. Both formulations are taken orally and are suitable for adults aged 18 and over for self-treatment purposes.

 

How Does Losec Work to Reduce Stomach Acid?

 

Understanding how Losec works can help you feel more confident about using it. The stomach lining contains specialised cells with tiny structures called proton pumps. These pumps are responsible for secreting hydrochloric acid into the stomach — which is useful for digestion, but problematic when there's too much of it.

  • Omeprazole is absorbed into the bloodstream after you swallow the capsule or tablet.
  • It travels to the acid-secreting cells in the stomach lining.
  • It irreversibly binds to and blocks the proton pumps in those cells.
  • This significantly reduces the volume of acid produced, lowering stomach acidity.
  • With less acid present, the oesophagus, stomach lining, and any ulcers present can begin to heal.

The effect builds over a few days of consistent use, so don't be discouraged if you don't notice full relief on day one. Most people experience meaningful symptom improvement within two to three days.

 

Who Is Losec 20mg Suitable For?

 

Losec is suitable for a broad range of adults experiencing acid-related conditions. It's particularly useful if lifestyle changes alone haven't been enough to manage your symptoms. That said, it's not right for everyone — and it's always worth checking with a pharmacist if you're unsure.

  • Adults aged 18 and over with frequent heartburn or acid reflux
  • People diagnosed with gastro-oesophageal reflux disease (GORD)
  • Patients with gastric or duodenal ulcers (under medical supervision)
  • Those taking NSAIDs (such as ibuprofen) who need stomach protection — you can find relevant pain relief options in our range
  • People with Zollinger-Ellison syndrome (a rare condition causing excess acid production)

 

How Does Losec Compare to Other Acid Reflux Treatments?

 

Feature Losec (Omeprazole 20mg) Antacids (e.g. Gaviscon)
Mechanism Blocks acid production at source Neutralises acid already present
Duration of effect Up to 24 hours per dose 1–3 hours per dose
Suitable for ulcer healing Yes No
Onset of full effect 2–3 days of regular use Within minutes

 

How Should Losec Be Stored and Is It Clinically Suitable for You?

 

Store Losec capsules and tablets below 25°C in a dry place, away from direct sunlight. Keep them in their original packaging and out of reach of children. Do not use after the expiry date printed on the pack. If you have any unused medicine, return it to your local pharmacy for safe disposal — never put it in household waste or flush it down the sink.

Before starting omeprazole 20mg, it's worth considering whether it's the right fit for your situation. If you've had previous allergic reactions to PPIs, or if you're taking medicines like clopidogrel or methotrexate, speak to a pharmacist or GP first. Losec is not recommended for children under 18 for self-treatment purposes.

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.

Losec Capsules & Tablets (Omeprazole) 20mg specifications
Treatment category Acid reflux, heartburn, gastric and duodenal ulcers, GORD
Active ingredient Omeprazole 20mg
Mechanism of action Proton pump inhibitor (PPI) — reduces gastric acid secretion
Drug class Proton pump inhibitor (PPI)
Preparation Gastro-resistant capsules and gastro-resistant tablets
Route of administration Oral
Strengths 20mg
Pack sizes 7, 14, and 28 capsules/tablets (varies by pack)
Suitable for Adults aged 18 and over
UK classification Pharmacy (P) medicine
Effective Acid reflux, heartburn, GORD, gastric ulcers, NSAID-associated ulcer prevention

Specifications of Losec Capsules & Tablets (Omeprazole) 20mg

 

What Is Losec and What Is It Used For?

 

Losec contains omeprazole 20mg, a proton pump inhibitor (PPI) used to reduce the amount of acid produced in the stomach. It is used to treat and relieve symptoms associated with excess stomach acid, including heartburn, acid regurgitation, and the discomfort of gastro-oesophageal reflux disease (GORD). It is also used to help heal gastric and duodenal ulcers, and to protect the stomach lining in people who take non-steroidal anti-inflammatory drugs (NSAIDs) regularly.

Omeprazole 20mg is one of the most commonly prescribed and purchased medicines in the UK for acid-related conditions. When used as directed, it provides reliable, sustained relief by targeting the root cause of excess acid rather than simply masking symptoms.

 

What Do You Need to Know Before Using Losec?

 

Before taking Losec, it's important to be aware of certain conditions and medicines that may affect whether it's safe for you to use.

Do not take Losec if you:

  • Are allergic to omeprazole or any other proton pump inhibitor (e.g. lansoprazole, pantoprazole, esomeprazole, rabeprazole)
  • Are allergic to any of the other ingredients listed in the patient information leaflet
  • Are taking medicines containing nelfinavir (used to treat HIV infection)
  • Are under 18 years of age (for self-treatment without medical supervision)

Speak to your doctor or pharmacist before taking Losec if you:

  • Have severe liver problems
  • Are due to have an endoscopy or urea breath test
  • Have previously had a skin reaction after taking a PPI
  • Are pregnant, planning to become pregnant, or breastfeeding
  • Have low magnesium levels (hypomagnesaemia)
  • Have ever been told you have osteoporosis or are at risk of bone fractures

Known drug interactions — tell your doctor or pharmacist if you are taking:

  • Clopidogrel (used to prevent blood clots)
  • Methotrexate (used for cancer or inflammatory conditions)
  • Warfarin or other anticoagulants
  • Digoxin (used for heart conditions)
  • Antifungal medicines such as ketoconazole or itraconazole
  • HIV medicines such as atazanavir or saquinavir
  • Rifampicin (an antibiotic)
  • St John's Wort (a herbal remedy)

 

How Should You Use Losec Correctly?

 

Always take Losec exactly as directed on the label or as advised by your pharmacist or doctor. Do not take more than the recommended dose. If you are unsure, ask your pharmacist.

  1. Take one Losec 20mg capsule or tablet once daily, ideally 30 to 60 minutes before a meal.
  2. Swallow the capsule or tablet whole with a full glass of water — do not crush, chew, or split it.
  3. If you have difficulty swallowing capsules, you may open the capsule and mix the granules with a small amount of non-carbonated water or slightly acidic juice (e.g. apple juice) — swallow immediately without chewing.
  4. Take Losec at the same time each day to maintain consistent acid suppression.
  5. Continue for the full recommended course, even if symptoms improve before the course ends.
Indication Age Group Dose Duration
Heartburn / acid reflux (self-treatment) Adults 18+ 20mg once daily Up to 14 days
GORD (under medical supervision) Adults 18+ 20mg once daily 4–8 weeks
Gastric or duodenal ulcer Adults 18+ 20mg once daily 4–8 weeks (as directed)
NSAID-associated ulcer prevention Adults 18+ 20mg once daily As directed by doctor

If you are self-treating heartburn and your symptoms do not improve after 14 days, stop taking Losec and consult your GP. Do not take it for longer than 14 days without medical advice. You might also find it helpful to browse our IBS and cramps range if your digestive symptoms are more complex.

 

What Are the Possible Side Effects of Losec?

 

Like all medicines, Losec can cause side effects, although not everyone gets them. Most side effects are mild and temporary.

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

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

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

  • Dizziness
  • Sleep disturbances (insomnia)
  • Skin rash or itching
  • Swollen ankles or feet (peripheral oedema)
  • Raised liver enzymes (detected on blood tests)
  • Low magnesium levels with long-term use

Stop taking Losec and seek immediate medical attention if you experience a severe allergic reaction — signs include swelling of the face, lips, tongue or throat, difficulty breathing, or a sudden skin rash with blistering. These reactions are rare but serious.

 

How Should You Store Losec?

 

  • Store below 25°C in a dry place, away from direct sunlight and moisture
  • Keep in the original packaging until use
  • Keep out of the sight and reach of children
  • Do not use after the expiry date printed on the pack
  • Return any unused medicine to your local pharmacy — do not dispose of via household waste or sink

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 Losec 20mg online in the UK?

You can buy Losec 20mg capsules and tablets online from Cured Pharmacy, a GPhC-registered UK online pharmacy. Simply add the product to your basket and complete a short health questionnaire before checkout. We dispatch quickly and discreetly to addresses across the UK.

How does omeprazole 20mg work in the body?

Omeprazole works by irreversibly blocking proton pumps in the stomach lining — the tiny structures responsible for secreting hydrochloric acid. By inhibiting these pumps, it significantly reduces the volume of acid your stomach produces. This allows irritated tissue and ulcers to heal while relieving symptoms like heartburn and regurgitation.

How do I take Losec capsules step by step?

Swallow one Losec 20mg capsule whole with a full glass of water — do not crush or chew it. Take it 30 to 60 minutes before a meal, ideally at the same time each day. If you struggle to swallow capsules, you can open them and mix the granules with a small amount of non-carbonated water, swallowing immediately without chewing.

What is the correct dose of Losec for acid reflux?

For self-treatment of heartburn and acid reflux in adults, the standard dose is one 20mg capsule or tablet once daily. You should not take it for more than 14 consecutive days without consulting a doctor or pharmacist. If symptoms persist beyond 14 days, seek medical advice rather than continuing to self-treat.

When is the best time to take Losec 20mg?

The best time to take Losec is in the morning, around 30 to 60 minutes before breakfast. Taking it before eating allows the medicine to be absorbed and reach the proton pumps while they are most active — which is when you start eating. Consistency matters, so try to take it at the same time every day.

What are the common side effects of Losec and how do I manage them?

The most common side effects of Losec include headache, diarrhoea, stomach pain, nausea, constipation, and wind. These are usually mild and tend to resolve on their own as your body adjusts. If any side effect is persistent or troublesome, speak to your pharmacist — they can advise whether you need to stop the medicine or try an alternative.

Who should not take Losec 20mg?

Losec is not suitable for people who are allergic to omeprazole or other proton pump inhibitors such as lansoprazole or pantoprazole. It should also be avoided by those taking nelfinavir (an HIV medicine) and is not recommended for self-treatment in children under 18. If you have severe liver disease or are pregnant, speak to your GP before using it.

What happens if I miss a dose of Losec?

If you forget to take a dose, take it as soon as you remember — unless it is nearly time for your next scheduled dose, in which case simply skip the missed one. Never take two doses at the same time to compensate. Missing the occasional dose is unlikely to cause problems, but try to maintain a consistent daily routine for best results.

Can I take Losec with other medicines?

Losec can interact with several medicines, including clopidogrel, methotrexate, warfarin, digoxin, certain antifungals, and some HIV medicines. Always tell your pharmacist or doctor about everything you are currently taking — including herbal remedies like St John's Wort. They can check for interactions and advise whether Losec is safe alongside your other medicines.

How long can you take Losec 20mg for?

For self-treatment of heartburn and acid reflux, Losec should not be used for more than 14 days without medical advice. For conditions like GORD or stomach ulcers, a doctor may prescribe it for four to eight weeks or longer. Long-term use requires regular medical review, as prolonged PPI use has been associated with low magnesium levels and a small increased risk of bone fractures.

Is Losec the same as omeprazole?

Yes — Losec is a branded version of omeprazole, containing the same active ingredient at the same 20mg strength. Both the branded and generic versions work in the same way and are considered therapeutically equivalent. Some people prefer the branded version for consistency, while others opt for generic omeprazole as a more cost-effective choice.

Can I take Losec during pregnancy or while breastfeeding?

You should speak to your GP or midwife before taking Losec if you are pregnant, trying to conceive, or breastfeeding. While omeprazole is sometimes used in pregnancy under medical supervision, it is not recommended for self-treatment without professional guidance. Your doctor can weigh up the risks and benefits for your specific situation.

What are the alternatives to Losec for acid reflux?

Alternatives to Losec include other proton pump inhibitors such as lansoprazole, pantoprazole, and esomeprazole, as well as H2 receptor antagonists like famotidine. For milder symptoms, antacids such as Gaviscon or Rennie may provide short-term relief. You can browse our indigestion treatments collection to compare available options.

Can Losec be used to protect the stomach when taking painkillers?

Yes — omeprazole 20mg is commonly used alongside NSAIDs such as ibuprofen or naproxen to protect the stomach lining from irritation and ulceration. If you regularly take NSAIDs for pain or inflammation, your doctor may recommend a PPI like Losec as a preventative measure. You can find relevant pain relief products in our range.

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

Research suggests that long-term PPI use (beyond several months) may be associated with a small increased risk of hypomagnesaemia (low magnesium), vitamin B12 deficiency, and a modest increase in fracture risk. The NHS advises that long-term use should be reviewed regularly by a GP to ensure it remains appropriate. If you are on long-term omeprazole, your doctor may periodically check your magnesium and bone health.

How Should You Use Losec Capsules and Tablets?

Taking Losec correctly makes a real difference to how well it works. Always follow the instructions on the pack or as directed by your pharmacist. Here is a step-by-step guide to using it properly:

Do not take more than one dose per day unless specifically directed by a doctor. If you accidentally take too much, contact your pharmacist or NHS 111 for advice.

What Is the Correct Dose of Losec for Your Condition?

The dose of Losec you need depends on what you are treating. For self-treatment of heartburn, one 20mg dose daily is standard. For conditions managed under medical supervision, your doctor may advise a different duration. Always follow their guidance.

When Is the Best Time to Use Losec?

Timing matters with Losec. The medicine works most effectively when taken 30 to 60 minutes before your first meal of the day — typically breakfast. This is because proton pumps are most active when stimulated by food, so having omeprazole in your system beforehand means it can block acid production at its peak. Taking it at a consistent time each morning also helps maintain steady levels in your body throughout the course of treatment.

If you forget to take your morning dose and have already eaten, take it as soon as you remember. If it is close to the time of your next dose, skip the missed one and carry on as normal the following day.

How Long Can You Use Losec For?

For self-treatment of heartburn and acid reflux, Losec should not be used for more than 14 consecutive days without speaking to a doctor or pharmacist. If your symptoms have not improved after two weeks, or if they return shortly after stopping, this could indicate an underlying condition that needs proper investigation. Do not simply restart another 14-day course without seeking advice first.

For conditions like GORD or stomach ulcers, your doctor may prescribe Losec for four to eight weeks or longer. Long-term use beyond this should be reviewed regularly by your GP to ensure it remains appropriate and to monitor for any potential effects such as low magnesium or changes in bone density.

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

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What Are the Most Common Side Effects of Losec?

Most people who take Losec tolerate it well, but like all medicines, it can cause side effects in some people. Common side effects affect up to 1 in 10 users and are generally mild. They often settle on their own as your body adjusts to the medicine.

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

What Are the Less Common Side Effects of Losec?

Less common side effects affect up to 1 in 100 people. While these are not frequent, it is worth being aware of them so you can recognise them if they occur. Contact your pharmacist if any of the following persist or concern you.

  • Dizziness or light-headedness
  • Sleep disturbances, including insomnia
  • Skin rash, itching, or hives
  • Swollen ankles or feet (peripheral oedema)
  • Raised liver enzymes (usually detected on blood tests)
  • Dry mouth
  • Low magnesium levels (hypomagnesaemia) — more likely with long-term use

What Are the Serious Side Effects of Losec?

Serious side effects are rare but require immediate medical attention. Stop taking Losec and call 999 or go to your nearest A&E if you experience signs of a severe allergic reaction (anaphylaxis), which may include swelling of the face, lips, tongue, or throat, difficulty breathing, or a sudden widespread skin rash with blistering or peeling.

Other serious but rare effects include severe skin reactions such as Stevens-Johnson syndrome, sudden kidney inflammation (interstitial nephritis), or significant changes in blood cell counts. These are uncommon, but if you develop unexplained bruising, persistent fever, or unusual fatigue while taking Losec, seek medical advice promptly.

What Should You Do If You Experience Side Effects of Losec?

For mild side effects such as headache or an upset stomach, these often resolve within a few days without any action needed. Staying well hydrated and taking the medicine before food (rather than on an empty stomach) may help reduce gastrointestinal discomfort. If a side effect is bothering you or does not improve, speak to your pharmacist — they can advise whether to continue, adjust timing, or switch to an alternative.

You can also report suspected side effects directly to the MHRA via the Yellow Card scheme at yellowcard.mhra.gov.uk. This helps improve medicine safety information for everyone.

Can Losec Interact With Other Medicines?

Yes — omeprazole can interact with a number of other medicines, which is why it is important to tell your pharmacist or doctor about everything you are taking. Key interactions include clopidogrel (where omeprazole may reduce its antiplatelet effect), methotrexate (where omeprazole may increase methotrexate levels in the blood), and warfarin (where monitoring of clotting time may be needed). HIV medicines such as atazanavir and nelfinavir should not be taken with omeprazole. Antifungals like ketoconazole and itraconazole may also be affected, as they rely on stomach acid for absorption.

If you are concerned about any side effects, contact your pharmacist or GP immediately.

Frequently Asked Question


You may feel some relief within a few hours, but maximum acid reduction occurs after 2 to 3 days of consistent use.


Yes, but take antacids at least 2 hours apart from Losec. Antacids give quick relief, while Losec works long-term.


Yes. It reduces acid travelling up the oesophagus, improving symptoms like throat irritation and chronic cough.

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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How fast does Losec 20mg start working?


You may feel some relief within a few hours, but maximum acid reduction occurs after 2 to 3 days of consistent use.

Can I take Losec with antacids?


Yes, but take antacids at least 2 hours apart from Losec. Antacids give quick relief, while Losec works long-term.

Can Losec help a sore throat caused by reflux?


Yes. It reduces acid travelling up the oesophagus, improving symptoms like throat irritation and chronic cough.