Sounds like 'oh-MEP-ra-zol'

Easy-to-read medicine information about omeprazole – what it is, how to take omeprazole safely and possible side effects.

Type of medicine

Also called

  • Medicine to reduce stomach acid
  • Belongs to a group of medicines known as proton pump inhibitors
  • Dr Reddy's Omeprazole®
  • Losec®
  • Omezol Relief®

 What is omeprazole?

Omeprazole reduces the amount of acid produced in your stomach. It belongs to a group of medicines known as proton pump inhibitors (PPIs). They are used to treat a number of conditions associated with high stomach acid affecting your stomach and gut, such as indigestion, reflux, and ulcers.  Omeprazole can also prevent ulcers from forming, or help the healing process where damage has already occurred. Omeprazole may be given together with antibiotics to get rid of Helicobacter pylori, a bacteria found in the stomach which can cause ulcers. Read more about Helicobacter pyloriOmeprazole may be used to prevent ulcers caused by medicines such as non-steroidal anti-inflammatory drugs (NSAIDs). Examples of NSAIDs are diclofenac, ibuprofen, naproxen. In New Zealand omeprazole is available as capsules and can be given as an injection in the hospital.  


  • The usual dose of omeprazole is 20 mg a day.
  • For some people, 10 mg a day is enough; others may need a higher dose of 40 mg a day.
  • The pharmacy label on your medicine will tell you how much omeprazole to take, how often to take it, and any special instructions. 
  • Your doctor will advise you how long to take omeprazole for, which can range from a few weeks to months. 

How to take omeprazole

  • Take omeprazole at the same time each day, usually in the morning.
  • Omeprazole is usually taken once a day, but some people may need to take it twice a day. Your doctor will tell you how often to take omeprazole.
  • Swallow the capsule whole with a glass of water. Do not crush or chew - the medicine doesn't work properly if the capsule is 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 without chewing.
  • Omeprazole can be taken before or after food, although taking it before food is best.
  • If you forget to take your dose, take it as soon as you remember. But, if it is nearly time for your next dose, just take the next dose at the right time. Do not take double the dose.

Avoid long-term use - choose wisely

If you don’t need them, PPIs like omeprazole should not be taken long term, because of the possible side effects. These include an increased risk of bone fractures, chest infections, kidney problems and nutrient deficiencies such as low magnesium. If you’ve been taking a PPI for reflux for longer than 4 to 8 weeks, and your symptoms seem to be well managed, it’s a good idea to talk to your health care provider about reviewing your medicine. They may recommend stepping down 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.

Read more about PPIs for heartburn and reflux Choosing Wisely, NZ

Precautions - before starting omeprazole

  • Are you pregnant, planning a pregnancy or breast-feeding?
  • Do you have problems with your liver?
  • Are taking any other medicines? This includes any medicines you are taking which you can buy without a prescription, as well as herbal and complementary medicines.

If so, it’s important that you tell your doctor or pharmacist before you start omeprazole. Sometimes a medicine isn’t suitable for a person with certain conditions, or it can only be used with extra care.

Possible side effects

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 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 restart omeprazole, you can use medicines that contain both an antacid and an anti-foaming agent, such as Mylanta P oral liquid, Acidex oral liquid or Gaviscon Double Strength tablets, They can be effective for treating rebound acid secretion. You can use these medicines to relieve the symptoms when they occur. Talk to your doctor or pharmacist about how to manage rebound acid secretion.

Other side effects

Side effects What should I do?
  • Stomach upset, feeling sick
  • Feeling bloated, gas in the tummy
  • Loose stool (mild diarrhoea)
  • Constipation
  • These are quite common when you first start taking omeprazole
  • Tell your doctor if troublesome 
  • Signs of low magnesium such as muscle cramps, weakness, tiredness, feeling irritable, and changes in heart beat
  • Increase your intake of magnesium-rich foods such as wholegrain cereals, green leafy vegetables (spinach, parsley, cabbage), peas, lean meats, nuts, seeds and bananas
  • Tell your doctor if troublesome — you may need a magnesium supplement
  • Severe diarrhoea (loose, watery, frequent stools)  
  • Omeprazole can increase the chance of getting severe diarrhoea (which may be caused by a bacteria called clostridium difficle)
  • Stop omeprazole and tell your doctor immediately 
  • Signs of an allergic reaction such as rash, fever, painful joints
  • Tell your doctor immediately or ring HealthLine 0800 611 116 
  • Worsening stomach problems such as really bad stomach pain, blood in the stool or black stools, vomit blood or dark coloured vomit
  • Tell your doctor immediately or ring HealthLine 0800 611 116 


Omeprazole may interact with a few medications and herbal supplements, so check with your doctor or pharmacist before starting omeprazole or before starting any new medicines.

Learn more

Medsafe Consumer Information Sheet: Losec Omezol Relief

New Zealand Formulary Patient Information: omeprazole


  1. Proton pump inhibitors: When is enough, enough? BPAC, June 2014
  2. Proton pump inhibitors and the risk of acute kidney injury. BPAC, July 2016
  3. Omeprazole New Zealand Formulary
Credits: Sandra Ponen, pharmacist. Last reviewed: 15 Jan 2019