Reviewed by Virginia Chachati MPharm
(2013, University College London)
GPhC Registration number: 2087654
Information last reviewed 23/03/2022
Omeprazole is a type of medicine called a proton pump inhibitor (PPI). It is used for the treatment of acid reflux, gastroesophageal reflux disease (GORD), heartburn and stomach ulcers.
Omeprazole is used to control conditions in which the stomach acid needs to be reduced. Omeprazole may be prescribed for GORD (gastroesophageal reflux disease), acid reflux (heartburn), stomach ulcers and erosive esophagitis.
Omeprazole works by decreasing the amount of acid in your stomach. It does this by blocking an acid-secreting cell in the stomach known as a proton pump. Blocking this cell directly reduces the amount of stomach acid being pumped into the stomach from where it is produced. Reducing the stomach acid helps to protect the stomach and surrounding structures and also reduces symptoms such as heartburn and reflux.
Omeprazole starts to work within 1 hour. However, it can take several days or weeks to experience the full effect depending on the severity of your condition.
Dose |
Take ONE capsule in the morning or as directed by your GP. |
Type of medicine | Proton pump inhibitor (PPI) |
Mechanism |
Reduces stomach acid, relieving acid reflux symptoms |
Available Size |
28 to 56 |
Available Strengths |
10mg & 20mg |
Active Ingredient |
Omeprazole |
Price |
From 25p per capsule |
Side Effects |
May include headaches, stomach discomfort, nausea and flatulence. |
Omeprazole is the active ingredient in omeprazole capsules.
The inactive ingredients in omeprazole capsules are sugar spheres (corn starch and sucrose), sodium lauryl sulfate, disodium phosphate, mannitol, hypromellose, polyethylene glycol 6000, talc, polysorbate 80, titanium dioxide, eudragit L30-D55 (poly(methacrylic acid, ethyl acrylate)), gelatin, quinine yellow (E104) and titanium dioxide (E171).
Please note: different brands of generic omeprazole could contain different inactive ingredients than those listed here. Check the patient information leaflet provided for full details.
Always take omeprazole as instructed by a doctor or pharmacist. It is usually taken once daily in the morning, although your doctor may recommend you take an additional evening dose for certain conditions.
Swallow one omeprazole capsule with water about an hour before eating. Dispersible tablets should be dissolved in a small glass of water before you swallow the mixture. If you forget to take a dose, don’t worry, just take the next one as planned. There is no need to take a double dose to make up for a missed one.
If you are taking over the counter omeprazole, you should not take it for more than 14 days without seeing a doctor. If you are taking prescription omeprazole, you should follow your doctor’s instructions. Some conditions may require longer-term treatment than others.
Prescription omeprazole usually comes as capsules. These capsules should be swallowed whole with water and should not be split or crushed. If you have difficulty swallowing capsules, you may want to try water-soluble omeprazole, like Losec MUPS, or orodispersible tablets which dissolve in the mouth.
Like any medicine, omeprazole can cause side effects in some patients. Common side effects of omeprazole, affecting up to 10% of people include headache, nausea, vomiting, diarrhoea, benign polyps in the stomach, stomach pain, constipation or flatulence (wind).
For other less common side effects, please read the patient information leaflet.
In rare cases, some people experience severe side effects such as an allergic reaction, liver problems and serious skin conditions. Stop taking omeprazole and seek immediate medical attention if you notice any of the following:
Omeprazole should be taken approximately an hour before eating. If this causes any sickness or nausea, try drinking small sips of water to stay hydrated and eat smaller portions at mealtimes.
Eating foods that are rich in fibre, exercise and drinking water will help to prevent constipation.
Stomach pain or discomfort can be soothed by holding a hot water bottle against your abdomen. You may also wish to avoid foods such as onions, peas, beans and lentils which can cause wind.
Omeprazole may not be suitable for everyone. Do not take omeprazole if you are allergic to any ingredients in this medication or other proton pump inhibitors. You should not take omeprazole if you are taking nelfinavir, a medication used for HIV treatment.
You should speak to your doctor before taking omeprazole if you experience unintended weight loss, problems swallowing, severe or persistent diarrhoea, stomach pain or indigestion, severe liver problems, a rash or skin reaction, vomiting or black stools. These symptoms could be a sign of a more severe condition which may need alternative treatment.
Do not take omeprazole if you are taking nelfinavir, an HIV medication. Other medications may also interact with omeprazole. Always tell your doctor if you are taking any other medicines, including over the counter treatments and herbal remedies. PPIs like omeprazole can affect the absorption of other medicines. This could prevent your other medicines from working properly, which could be dangerous.
Alcohol is a common cause of acid reflux. Therefore, it is best to avoid alcohol when taking omeprazole. However, there is no direct danger associated with drinking alcohol while taking omeprazole.
There are many different reflux medicines available. Most belong to the same family of medicines PPIs such as esomeprazole and pantoprazole. Alternatively, there are other over the counter treatments such as antacids which can neutralise stomach acid to reduce acidity.
Omeprazole capsules are the most commonly available form of omeprazole on prescription. However, for people who have difficulty swallowing tablets, there are tablets available that can be dissolved in water. Losec is a branded version of omeprazole. It is available in orodispersible tablets which are placed in the mouth and dissolved on the tongue. Liquid omeprazole is available for children who are unable to swallow tablets.
Losec is a brand name for the generic medicine called omeprazole. Both contain omeprazole as the active ingredient and work in exactly the same way, although the generic version is cheaper.
There is very little difference between esomeprazole and omeprazole. There is some evidence that suggests that esomeprazole may be slightly better at acid control. However, other studies have not found any difference at all. The choice to take esomeprazole or omeprazole may be down to personal preference and cost.
There is little difference between lansoprazole and omeprazole in the relief of heartburn and reflux symptoms. However, it has been found that omeprazole is more effective in reducing the acidity of stomach acid than lansoprazole. As this does not have any significant effect on symptoms, the choice is largely down to personal preference and cost.
You can buy omeprazole 20mg tablets over the counter, but omeprazole 20mg capsules are only available on prescription. Over the counter omeprazole can be used to treat acid reflux if you experience it more than twice a week. You should not take over the counter omeprazole for more than two weeks without speaking to a doctor. Prescription omeprazole is available in a variety of doses (10 mg, 20 mg, 40 mg) and in larger pack sizes.
A hiatus hernia occurs when part of your stomach is pushed through the diaphragm at the bottom of your chest. This makes it more likely that you will experience acid reflux and heartburn. Omeprazole is commonly used to treat acid reflux caused by a hiatus hernia. If you have a hiatus hernia, you may want to discuss omeprazole, or similar medications, with your doctor.
You should wait at least one hour after taking omeprazole before you drink coffee. This should give the medicine enough time to absorb and protect you from reflux.
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