If you are trying to understand the different omeprazole strengths, or wondering whether 10mg, 20mg or 40mg may be appropriate for your situation, this guide explains the differences in a clear and straightforward way.
It also covers what the different strengths are generally used for, how long omeprazole is commonly taken for, the usual limits for over the counter (OTC) treatment, and when it is important to seek advice from a pharmacist or prescriber.
This guide cannot tell you which dose is right for you. The most appropriate dose depends on your symptoms, medical history and any other medicines you take, so this decision should always be made by a pharmacist or prescriber following an individual assessment.
It also explains what omeprazole is, the strengths available in the UK, how it compares with other acid reducing medicines, and when it is time to seek professional advice rather than continuing to self treat.
Key Facts About Omeprazole at a Glance
| Fact | Detail |
|---|---|
| Drug class | Proton pump inhibitor (PPI) |
| Available strengths | 10mg, 20mg, 40mg |
| Formulations | Capsules, gastro-resistant tablets, dispersible tablets (Losec MUPS), liquid/oral suspension |
| Common brand name | Losec (original branded omeprazole) |
| OTC availability | 20mg only, for short-term self-treatment |
| OTC self-treatment limit | Up to 2 weeks without checking with a doctor |
| Common conditions treated | Heartburn, GORD, stomach ulcers, H. pylori infection (with antibiotics), gastroprotection alongside NSAIDs |
| Typical ulcer treatment course | 4 to 8 weeks, as advised by NHS guidance |
What Is Omeprazole? A Proton Pump Inhibitor That Reduces Stomach Acid
Omeprazole is a proton pump inhibitor (PPI), a type of medicine that reduces the amount of acid your stomach produces. It works by blocking the proton pumps, which are enzymes in the stomach lining responsible for producing stomach acid. By lowering acid levels, omeprazole can help the oesophagus and stomach lining heal while relieving symptoms caused by excess stomach acid.
It is commonly used to treat conditions such as heartburn, gastro-oesophageal reflux disease (GORD), stomach ulcers and, alongside antibiotics, Helicobacter pylori (H. pylori) infection. In American English, GORD is often referred to as gastroesophageal reflux disease (GERD).
Omeprazole is also available as a liquid formulation, which may be suitable for children or for people who have difficulty swallowing capsules or tablets.
What Strengths Does Omeprazole Come In?
In the UK, omeprazole is available in 10mg, 20mg and 40mg strengths. It comes in several formulations, including capsules, gastro resistant tablets (such as Losec MUPS) and a liquid formulation for people who need an alternative to tablets or capsules.
Each strength is generally used for different situations, depending on the condition being treated, the severity of symptoms and your individual response to treatment. The most appropriate strength should always be decided by a pharmacist or prescriber following an individual clinical assessment, rather than being chosen on your own.
Omeprazole Strengths at a Glance
| Strength | Typical availability | General association |
|---|---|---|
| 10mg | Prescription | Often used for lower-intensity or step-down treatment, at a prescriber's discretion |
| 20mg | Over-the-counter and prescription | The most commonly used standard strength for acid reflux and heartburn |
| 40mg | Prescription only | Used for more severe presentations, at a prescriber's discretion |
How much omeprazole you need, and how long you should take it for, depends on why you are taking it, the strength prescribed and your individual circumstances.
Always read the patient information leaflet supplied with your medicine and follow the instructions on the packaging. If you are unsure how or when to take omeprazole, speak with your pharmacist or prescriber for advice.
Treatment suitability depends on an individual clinical assessment.
Why Your Omeprazole Dose Is Not a DIY Decision
The right omeprazole dose is not the same for everyone. It depends on several factors, including your symptoms, how severe they are, how you have responded to treatment in the past, your age, and any other medical conditions or medicines you take.
That is why your pharmacist or prescriber will decide the most appropriate strength and treatment duration for you, rather than relying on general advice online.
What Is Omeprazole Generally Used For?
Heartburn and Occasional Acid Reflux
Omeprazole 20mg is commonly used to treat heartburn and occasional acid reflux. Depending on your circumstances, it may be available over the counter for short term use or prescribed by a healthcare professional.
If your symptoms continue, return after treatment or become more frequent, speak with your pharmacist or prescriber for further advice.
Gastro Oesophageal Reflux Disease (GORD)
For people with gastro oesophageal reflux disease (GORD) or more frequent reflux symptoms, a prescriber will decide the most suitable dose and treatment duration based on your individual needs.
Treatment may be recommended for longer than a short over the counter course, with regular reviews to check that it continues to be appropriate.
Gastric and Duodenal Ulcers
Omeprazole is one of the proton pump inhibitors (PPIs) commonly used to treat stomach ulcers, including gastric ulcers (in the stomach lining) and duodenal ulcers (in the first part of the small intestine).
Treatment is often prescribed for 4 to 8 weeks, although the exact dose and length of treatment depend on the cause of the ulcer, its severity and your individual clinical assessment.
Helicobacter pylori (H. pylori) Eradication
If a stomach ulcer or related symptoms are linked to Helicobacter pylori (H. pylori) infection, omeprazole may be prescribed alongside a combination of antibiotics.
The medicines, doses and treatment length are chosen by your prescriber based on factors such as the antibiotics being used, any allergies you may have and current treatment guidance.
Severe Reflux in Children
A liquid formulation (oral suspension) of omeprazole is available for children who need treatment for severe reflux or who cannot swallow tablets or capsules.
Treatment in children should always be supervised by a doctor. The most suitable formulation and dose are based on the child's age, weight and individual clinical assessment.
Erosive Oesophagitis and Rarer Indications
Omeprazole may also be prescribed for erosive oesophagitis, where acid reflux has caused damage to the lining of the oesophagus.
It is also used to treat less common conditions, such as Zollinger Ellison syndrome, where the stomach produces unusually high levels of acid.
These conditions are managed by a specialist, who will decide the most appropriate dose and treatment plan. In some cases, higher doses or a different dosing schedule may be needed, with treatment reviewed regularly to ensure it remains appropriate.
Gastroprotection Alongside NSAIDs, Aspirin or Antiplatelet Medicines
Omeprazole is not only prescribed for acid reflux. It is also commonly used to help protect the stomach in people taking certain medicines over a longer period.
This may include NSAIDs (non steroidal anti inflammatory drugs) such as ibuprofen or naproxen, long term aspirin, or antiplatelet medicines, particularly for people who have a higher risk of developing stomach or duodenal ulcers. This can include people who:
- Have a history of stomach ulcers.
- Are aged 65 or over.
- Have other factors that increase their risk of stomach or duodenal ulcers.
In these situations, omeprazole may be prescribed to help reduce the risk of stomach damage linked to these medicines. If you have been prescribed omeprazole alongside a painkiller or blood thinner, this is often the reason.
Omeprazole Brand Names and Terminology
Omeprazole is the generic name of the medicine. Losec is the original branded version, while Losec MUPS is a dispersible tablet formulation.
You may also come across other brand names depending on the manufacturer. Although the packaging may differ, the active ingredient remains the same.
A few other terms you may see include:
- Gastro resistant – A special coating that helps protect the medicine from stomach acid so it can be absorbed in the small intestine.
- PPI (proton pump inhibitor) – The group of medicines that omeprazole belongs to, alongside esomeprazole, lansoprazole, pantoprazole and rabeprazole.
Over the Counter Omeprazole: What You Need to Know
Certain 20mg omeprazole products can be bought over the counter from pharmacies and some supermarkets in the UK for the short term treatment of occasional heartburn and acid reflux.
Prescription omeprazole is different, as it may be supplied in 10mg, 20mg or 40mg strengths, depending on your condition and your prescriber's assessment.
If you buy omeprazole yourself, NHS guidance recommends not taking it for longer than 2 weeks without speaking to a doctor.
If your symptoms have not improved after 2 weeks, or they get worse at any point, speak with your pharmacist or GP rather than continuing treatment or increasing the dose yourself.
How Long Does Omeprazole Take to Work, and How Long Is a Typical Course?
Omeprazole is taken by mouth and, depending on the product and your healthcare professional's advice, it may be recommended to take it before food. Always follow the instructions in the patient information leaflet or those provided by your prescriber or pharmacist.
Unlike antacids, omeprazole works by reducing the amount of acid your stomach produces rather than neutralising acid that is already there. Because of this, it can take a few days before you notice the full effect.
How long you need to take omeprazole depends on the condition being treated. Some people only need treatment for a few days or weeks, while others may require a longer course under medical supervision.
For example, stomach ulcers are commonly treated with a course of 4 to 8 weeks, although this may vary depending on your individual circumstances.
Your prescriber or pharmacist will advise you how long to take omeprazole. If you are taking it over a longer period, your treatment should be reviewed regularly to make sure it continues to be appropriate.
Omeprazole Compared With Other Acid-Reducing Medicines
If you're comparing proton pump inhibitor PPI medicines like omeprazole against esomeprazole, lansoprazole or pantoprazole, or weighing a PPI against a different class of drug, H2-receptor antagonists such as famotidine, the table below sets out the general pattern for each.
Comparison
| Medicine | Type | Typical dosing pattern | Notes |
|---|---|---|---|
| Omeprazole | PPI | Once daily, usually in the morning (twice daily for specific conditions) | Certain 20mg products available OTC ; prescription strengths include 10mg, 20mg and 40mg |
| Esomeprazole | PPI | Once daily, with or without food | A related but chemically distinct PPI, not a concentrated form of omeprazole |
| Lansoprazole | PPI | Once daily, at least 30 minutes before a meal | Capsules can be opened and dispersed for those with swallowing difficulties |
| Pantoprazole | PPI | Once daily, about an hour before a meal | Often chosen for a favourable drug interaction profile |
| Famotidine | H2-receptor antagonist | Once or twice daily | Works differently to PPIs, blocking histamine receptors rather than proton pumps; sometimes used as step-down therapy |
This comparison is for general information only and does not suggest that one medicine is more effective than another. The right option, strength and duration depend on individual clinical circumstances and should be confirmed with a pharmacist or prescriber.
Administration: How Omeprazole Should Be Taken
Omeprazole capsules and gastro resistant tablets should be swallowed whole with water. Do not crush, chew or open them, as the special coating helps protect the medicine until it reaches the small intestine, where it can be absorbed properly.
If you have difficulty swallowing capsules, some formulations, such as Losec MUPS, can be dispersed in water by following the instructions in the patient information leaflet.
Some capsule formulations may also be mixed with a small amount of soft, slightly acidic food, such as apple sauce, and swallowed straight away without chewing. However, this does not apply to every product, so always check the patient information leaflet or ask your pharmacist before doing this.
Many people take omeprazole once a day in the morning, although some people may be advised to take it twice a day. Always follow the instructions provided by your prescriber or in the patient information leaflet.
Missed Dose and Taking Too Much Omeprazole
If you miss a dose of omeprazole, take it as soon as you remember unless it is nearly time for your next dose. If it is almost time for your next dose, skip the missed dose and continue with your usual schedule.
Do not take two doses together to make up for a missed dose.
Taking more omeprazole than recommended does not always cause serious problems, but if you have taken too much and feel unwell, or you are worried, seek advice from your pharmacist, NHS 111 or your doctor. If symptoms are severe, seek urgent medical attention.
Always check the patient information leaflet supplied with your medicine, as instructions may vary slightly depending on the formulation.
Side Effects of Omeprazole
Like all medicines, omeprazole can cause side effects, although not everyone experiences them.
Common side effects include headache, nausea, diarrhoea and stomach pain. These are often mild and may improve as your body gets used to the medicine.
If you have diarrhoea, drink plenty of fluids to help prevent dehydration. If your diarrhoea is severe, lasts for more than a few days or you are concerned, speak with your doctor or pharmacist. Severe diarrhoea or vomiting lasting more than 24 hours may also affect how well the combined or progestogen only contraceptive pill works, so check your contraceptive guidance or speak with a healthcare professional for advice.
Although less common, there are some side effects that need medical attention.
Tell your doctor promptly if you notice any of the following:
- Allergic reaction: Symptoms may include swelling of the face, lips, tongue or throat, difficulty breathing or swallowing, an itchy rash or feeling faint. Seek urgent medical attention if these occur.
- Low magnesium levels: Long term use of omeprazole has been linked with low magnesium levels in some people. Symptoms may include tiredness, confusion, drowsiness, dizziness, muscle twitches, muscle spasms, shakiness or an irregular heartbeat. Your doctor may recommend blood tests if needed, particularly if you also take medicines such as digoxin or certain diuretics.
- Low vitamin B12 levels: Long term treatment may increase the risk of vitamin B12 deficiency in some people. Symptoms can include ongoing tiredness, a sore red tongue, sore throat, mouth ulcers or pins and needles.
- Bone fractures: Long term use of PPIs has been associated with a small increase in the risk of bone fractures, particularly in people with other risk factors such as osteoporosis. If you are taking omeprazole long term, your doctor may review your treatment regularly.
- Skin reactions with joint pain: In rare cases, PPIs such as omeprazole have been linked to a condition called subacute cutaneous lupus erythematosus. Symptoms may include a rash on areas exposed to sunlight, sometimes with joint pain, chest pain or swollen glands. Speak with your doctor promptly if you notice these symptoms.
- Fundic gland polyps: These are small, usually harmless growths in the stomach lining that may be seen more often in people taking PPIs over a long period. They are usually found during investigations such as an endoscopy and your doctor will advise if any follow up is needed.
This is general safety information and does not include every possible side effect. For a full list, read the patient information leaflet included with your medicine. If you experience any side effects that bother you, do not go away or feel serious, speak with your pharmacist, doctor or prescriber.
Omeprazole does not usually affect your ability to drive or operate machinery. However, if you feel dizzy or notice any changes to your vision, wait until you feel better before driving or using machinery.
If your symptoms continue, get worse or new symptoms develop, speak with a healthcare professional, even if treatment seems to be helping. Symptoms such as difficulty swallowing, unexplained weight loss or vomiting blood should always be assessed by a doctor rather than managed by taking a higher over the counter dose or continuing to self treat.
If you take omeprazole for a long period, your GP or prescriber will usually review your treatment regularly to make sure it is still appropriate. Where suitable, they may recommend reducing to the lowest effective dose or using treatment only when needed.
Omeprazole and Other Medicines: Interactions and Precautions
Omeprazole can interact with some medicines, so it is important to tell your doctor, pharmacist or prescriber about everything you are taking before starting treatment. This includes prescription medicines, over the counter medicines, herbal remedies, vitamins and supplements.
Some interactions to be aware of include:
- Clopidogrel: Omeprazole can reduce how well clopidogrel works. If you take clopidogrel, your prescriber may recommend a different PPI, such as pantoprazole, if acid reducing treatment is needed.
- St John's Wort: This herbal remedy may reduce the effectiveness of omeprazole and is generally not recommended while taking it.
- Painkillers: Paracetamol can generally be taken with omeprazole. If you regularly take ibuprofen or other anti inflammatory medicines, speak with a healthcare professional for advice, as these medicines can irritate the stomach.
These are only some of the possible interactions. Always read the patient information leaflet and let your healthcare professional know about all the medicines and supplements you take.
Omeprazole may be suitable during pregnancy or breastfeeding, but you should speak with your pharmacist, doctor or prescriber before taking it.
If you are breastfeeding, side effects in breastfed babies are considered uncommon. However, if you have any concerns about your baby, speak with a healthcare professional.
A clinical assessment is also particularly important for older adults, people with liver disease, or those with other medical conditions that may affect how the medicine works. Your prescriber will consider your medical history and current medicines before deciding whether omeprazole is suitable for you.
Why Ethnicity Can Be Relevant to Omeprazole Dosing
People process omeprazole differently, partly because of natural genetic differences that affect how the body breaks down the medicine. These differences vary between individuals and can be more common in some populations.
This is one of several factors a prescriber may consider when deciding the most appropriate dose for you. Your age, liver function, other medicines you take and your overall health are also taken into account. This is why omeprazole dosing should always be based on an individual clinical assessment rather than self selecting a dose.
This is general safety information and not individual medical advice. If you have any questions about your symptoms, treatment or other medicines you are taking, speak with your doctor, pharmacist or prescriber. Always follow the dose and treatment duration given in your patient information leaflet, prescription or by your healthcare professional.
When to Get Professional Medical Advice
Most people take omeprazole for occasional heartburn or acid reflux without any problems. However, there are times when it is important to seek medical advice rather than continuing to self treat.
Speak with a healthcare professional if:
- Your symptoms have not improved or have become worse after 2 weeks of over the counter treatment.
- You experience any serious side effects, especially signs of an allergic reaction, unexplained bruising or bleeding, or a new skin rash with joint pain.
- You have difficulty swallowing, unexplained weight loss, vomiting blood or black stools. These symptoms should always be assessed promptly by a healthcare professional.
- You are starting a new medicine, including herbal remedies or supplements, while taking omeprazole.
- You are pregnant, breastfeeding, an older adult, have liver disease or another medical condition that may affect your treatment.
If you are unsure what to do, speak with your pharmacist, GP or NHS 111 for advice. They can assess your symptoms and help you decide on the most appropriate next steps. General information can be helpful, but it should not replace advice from a healthcare professional who understands your individual circumstances.
