Sounds like 'oh-MEP-ra-zol'

Key points about omeprazole

  • Omeprazole is used to treat problems affecting your stomach and gut, such as indigestion, reflux and ulcers.
  • It works by reducing stomach acid.
  • Omeprazole belongs to a group of medicines known as proton pump inhibitors.
  • It is also called Losec.
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Omeprazole reduces the amount of acid produced in your stomach. It belongs to a group of medicines known as proton pump inhibitors (PPIs).

  • Omeprazole is used to treat conditions associated with high levels of stomach acid, such as indigestion, reflux and ulcers. It can prevent ulcers from forming or help the healing process where damage has already occurred.
  • Omeprazole can be used to prevent ulcers caused by medicines such as non-steroidal anti-inflammatory drugs (NSAIDs). Examples of NSAIDs are diclofenac, ibuprofen, and naproxen.
  • It can also be given together with certain antibiotics to get rid of Helicobacter pylori, a bacteria found in your stomach that can cause ulcers.
  • For information on omeprazole in children, see omeprazole information for parents and carers.(external link)

In New Zealand omeprazole is available as capsules, tablets, liquid suspension and an injection (usually used in hospital). 

Omeprazole is usually available on prescription but for the short-term relief of heartburn and acid reflux, the tablets and capsules (10mg and 20mg) can be bought in limited quantities without a prescription from your pharmacy (over-the counter or OTC).

However, don't use it if you:

  • are under 18 years old
  • are experiencing weight loss
  • have vomiting or difficulty swallowing
  • have symptoms of gut bleeding, eg, blood in your poo or black or dark coloured poo, vomiting blood or dark-coloured vomit
  • are pregnant.

If any of these apply to you, talk to your doctor or pharmacist for medical advice. 

  • Omeprazole is usually taken once a day for the relief of heartburn, acid reflux, or ulcers. Take omeprazole at about the same time each day, preferably in the morning.
  • If you are taking omeprazole for either Helicobacter pylori eradication or for Zollinger-Ellison syndrome, it is likely you will be asked to take it twice a day.
  • Omeprazole can be taken before or after food, although taking it before food is best.


  • Swallow the capsule whole with a glass of water. The granules inside won't work properly if they are crushed or chewed. 
  • If you have difficulty swallowing the capsule, you can open it and sprinkle the pellets over some fruit juice or yoghurt and swallow the granules without chewing.


  • Swallow the omeprazole tablet with a drink of water, or it can be dissolved in a drink if you have difficulty swallowing tablets.

Here are some things to know when you're taking omeprazole. Other things may be important as well, so ask your healthcare provider what you should know about.

Avoid long-term use of omeprazole

If you don’t need them, omeprazole should not be taken long term, because of the possible side effects. There may be a small increased risk of bone fractures, chest infection, gut infection and nutrient deficiencies such as low magnesium and vitamin B12. 

If you’ve been taking omeprazole for reflux for longer than 4–8 weeks, and your symptoms seem to be well managed, it’s a good idea to talk to your healthcare provider about reviewing your medicine. They may recommend reducing your treatment. This could include:

  • Reducing your daily dose of omeprazole.
  • Taking omeprazole only when you experience the symptoms of heartburn and reflux (also known as on-demand therapy).
  • Stopping treatment completely, as your symptoms may not return. It may be best to reduce the dose over a few weeks before stopping.

Read more about PPIs for heartburn and reflux.(external link)

Taking other medicines

Omeprazole may be affected by medicines or herbal supplements, so check with your doctor or pharmacist before starting any new medicines.

Having an endoscopy

Ask your doctor if you should stop taking omeprazole a few weeks before your endoscopy. This is because omeprazole may hide some of the problems that would usually be spotted during an endoscopy.

Like all medicines omeprazole can cause side effects, although not everyone gets them. Often side effects improve as your body adjusts to the new medicine.

Rebound acid secretion when stopping

When omeprazole is stopped, a common side effect is rebound acid secretion, where the acid secretion in your stomach increases significantly. This should return to normal within 2 weeks. Because the symptoms of rebound acid secretion are the same as for reflux (such as indigestion, discomfort and pain in your upper stomach and chest, feeling sick and an acid taste in your mouth), it can form an ongoing loop where stopping omeprazole treatment creates the need to start it again.

Rather than restarting omeprazole, your doctor may advise you to use antacids such as Acidex, Mylanta or Gaviscon. These can be effective for treating rebound acid secretion so talk to your doctor or pharmacist if you experience it.

Other side effects

Side effects What should I do?
  • Stomach upset, feeling sick
  • Feeling bloated, gas in your abdomen (tummy), farting
  • Loose stool (mild diarrhoea)
  • Constipation
  • These are quite common when you first start omeprazole.
  • If you feel sick, try taking omeprazole with or after a meal or snack. 
  • Tell your doctor if these side effects bother you.
  • Signs of low magnesium, such as muscle cramps, weakness, tiredness, feeling irritable and tingling or numbness
  • If you take omeprazole for more than 3 months, the levels of magnesium in your blood may fall.
  • Tell your doctor if you get these side effects.
  • Signs of low vitamin B12 such as feeling very tired, a sore and red tongue, mouth ulcers and pins and needles.
  • This is most likely if you take omeprazole long-term, on an ongoing basis.
  • Tell your doctor if you get these side effects.
  • Severe or ongoing diarrhoea (loose, watery, frequent stools)  
  • This can be a sign of an inflamed bowel. 
  • Tell your doctor immediately.
  • Fever and joint pain along with a red skin rash.
  • Rash on parts of your body exposed to the sun, such as your arms, cheeks and nose.  
  • Omeprazole can cause rare conditions called subacute cutaneous lupus erythematosus and drug-induced photo-sensitivity reactions. They can happen even if you have been taking omeprazole for a long time.
  • Tell your doctor immediately or phone Healthline 0800 611 116. 
For more information on side effects, see the consumer information leaflets below. 
Did you know that you can report a medicine side effect to the Centre for Adverse Reactions Monitoring (CARM)? Report a side effect to a product.(external link)

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Credits: Sandra Ponen, Pharmacist, Healthify He Puna Waiora. Healthify is brought to you by Health Navigator Charitable Trust.

Reviewed by: Angela Lambie, Pharmacist, Auckland

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