Omeprazole is a commonly prescribed medicine. It belongs to a group of medicines called proton pump inhibitors (PPIs), which work by reducing the amount of acid produced in the stomach. It is commonly used to treat conditions such as GORD, stomach ulcers and heartburn.
Like all medicines, omeprazole has important safety information to consider, including possible side effects, medicine interactions and situations where extra care may be needed.
Whether you are looking for information about omeprazole warnings, precautions, contraindications, drug interactions or long term use, this guide explains key points to know before taking the medicine.
It also covers commonly searched topics such as:
NHS safety advice
Long term use and possible risks
Alcohol and omeprazole
Medicine interactions
Overdose concerns
Expired omeprazole
Contraindications
Patient Information Leaflet guidance
This article is for general information only and does not replace personalised advice from a qualified healthcare professional.
What Is Omeprazole?
Omeprazole belongs to a group of medicines called proton pump inhibitors (PPIs). It works by reducing the amount of acid produced by the stomach, helping to treat conditions linked to excess stomach acid.
It may be prescribed for adults and, in some cases, children to treat conditions such as:
- Gastro oesophageal reflux disease (GORD)
- Heartburn and acid reflux
- Stomach (gastric) ulcers
- Duodenal ulcers
- Prevention of ulcers linked to certain medicines
- Helicobacter pylori infection, alongside antibiotics and other medicines, to help treat ulcers associated with the infection
- Zollinger Ellison syndrome, a condition where the body produces too much stomach acid
For people with GORD, omeprazole may help reduce symptoms and allow acid related irritation or damage to the oesophagus to heal.
Omeprazole is usually taken once or twice daily, depending on the condition being treated and the advice of your prescriber. Tablets or capsules should generally be swallowed whole with water.
The length of treatment depends on your condition and should always follow the guidance provided by your healthcare professional.
Is Omeprazole Safe?
For most adults, omeprazole is generally considered safe and well tolerated when taken as directed. It has been widely prescribed and used in clinical practice for many years.
However, like all medicines, omeprazole may not be suitable for everyone, and safety can depend on factors such as:
- Your age
- Existing medical conditions
- Other medicines you take
- How long you use it for
- The dose prescribed
- Your individual response to treatment
For short term use, side effects are usually mild and temporary. If omeprazole is used for a longer period, your healthcare professional may review your treatment regularly to check that it remains appropriate for you.
Important Warnings About Omeprazole
Before taking omeprazole, it's important to understand several key safety warnings.
Do Not Ignore Persistent Symptoms
Omeprazole can relieve heartburn and indigestion, but it may also mask symptoms of more serious underlying conditions. If your symptoms persist, worsen or recur after treatment, seek medical advice rather than continuing to self-medicate. Over-the-counter omeprazole should not usually be taken for longer than 14 days without seeking medical advice .
Long-Term Use Requires Regular Review
If you take omeprazole for several months or longer, your healthcare professional may review your treatment from time to time to check that it is still appropriate.
Long term use of omeprazole has been associated with an increased risk of:
- Vitamin B12 deficiency
- Low magnesium levels (hypomagnesaemia), which may cause symptoms such as muscle cramps, weakness, or muscle twitches
- Bone fractures, particularly in people with osteoporosis or those using higher doses for longer periods
- Certain gastrointestinal infections, including Clostridioides difficile
These risks do not affect everyone, but they may become more relevant with longer term use. Regular medication reviews can help ensure that your treatment remains suitable for your individual needs.
Do Not Stop Suddenly Without Advice
If you have been taking omeprazole for an extended period, stopping abruptly may lead to rebound acid hypersecretion, where the stomach temporarily produces more acid than before. Your clinician may recommend reducing the dose gradually rather than stopping suddenly.
Omeprazole Precautions
Tell your doctor, pharmacist, or healthcare professional before taking omeprazole if you:
- Have liver disease
- Have osteoporosis or an increased risk of fractures
- Have previously had an allergic reaction to omeprazole or another proton pump inhibitor (PPI)
- Are pregnant, planning to become pregnant, or breastfeeding
- Have unexplained weight loss, ongoing vomiting, or difficulty swallowing
- Have black stools or signs of gastrointestinal bleeding
- Are due to have certain blood tests or medical investigations
Sharing your full medical history helps your healthcare professional decide whether omeprazole is suitable and how it should be used safely.
Contraindications for Omeprazole
Omeprazole may not be suitable for everyone.
You should always discuss your medical history with a healthcare professional before starting treatment.
Omeprazole may not be appropriate if you:
- Have had an allergic reaction to omeprazole or another proton pump inhibitor.
- Are taking medicines that should not be combined with omeprazole (such as nelfinavir).
- Have certain liver conditions that require careful monitoring or dose adjustment.
Other medical conditions may require additional assessment before treatment begins.
Omeprazole Drug Interactions
Like many medicines, omeprazole can interact with other treatments.
Always tell your healthcare professional about all medicines you take, including prescription drugs, other medications, herbal remedies, and supplements.
Omeprazole can interact with several medicines, including :
- Blood-thinning medicines (such as warfarin)
- Clopidogrel
- Methotrexate
- Digoxin
- Phenytoin
- Diazepam
- Tacrolimus
- Certain antifungal medicines
- HIV medicines, including nelfinavir (contraindicated)
- St John's wort
Your clinician may adjust treatment or recommend additional monitoring where appropriate.
Can You Drink Alcohol with Omeprazole?
No clinically significant interaction between omeprazole and alcohol is known .
However, alcohol may irritate the stomach lining and worsen symptoms such as heartburn, indigestion and acid reflux. If you notice that alcohol triggers your symptoms, reducing your intake may improve symptom control while taking omeprazole.
Can You Overdose on Omeprazole?
People often search:
- Can you overdose on omeprazole?
- Can you overdose on omeprazole 20 mg?
Taking more omeprazole than prescribed is unlikely to cause serious harm in most cases, but it may increase the risk of side effects . However, taking too much omeprazole can lead to symptoms such as dizziness, drowsiness, nausea, blurred vision or confusion.
If you or someone else has taken substantially more omeprazole than prescribed, contact NHS 111 for urgent advice. In an emergency or if severe symptoms develop, seek urgent medical advice, attend your nearest emergency department or call 999 if severe symptoms develop .
What If You Miss a Dose?
If you forget to take omeprazole, follow your regular dosing schedule and take the missed dose as soon as you remember unless it is nearly time for your next dose.
Do not take a double dose to make up for a missed one, as this increases the risk of side effects without improving treatment effectiveness.
Key Takeaways
- Omeprazole is generally considered safe when used as directed by a healthcare professional .
- Long-term treatment should be reviewed periodically because of potential risks such as vitamin B12 deficiency, low magnesium levels and bone fractures.
- Inform your healthcare professional about all medicines you take to reduce the risk of interactions.
- Do not stop long-term omeprazole suddenly without medical advice.
- Seek urgent medical attention if you take substantially more omeprazole than prescribed or develop symptoms of a serious allergic reaction.
Omeprazole Side Effects and Precautions
Like all medicines, omeprazole can cause side effects, although many people experience none or only mild symptoms. Most common side effects improve as your body adjusts to treatment.
Common Side Effects
Some of the more frequently reported side effects include:
- Headache
- Stomach pain
- Nausea or vomiting
- Diarrhoea
- Constipation
- Flatulence (wind)
These side effects are usually mild and temporary. If they persist or become troublesome, speak to a healthcare provider rather than stopping treatment without advice.
Serious Side Effects
Although serious side effects are uncommon, seek urgent medical advice if you develop:
- Difficulty breathing or swelling of the face, lips, tongue, or throat, which may indicate a serious allergic reaction
- Severe or persistent diarrhoea, especially if it is bloody or accompanied by stomach pain
- Yellowing of the skin or eyes, which may be a sign of liver problems
- Unexplained bruising or bleeding
- A severe skin rash, blistering, or peeling
- Muscle cramps, twitches, tremors, or unusual weakness, which may be linked to low magnesium levels
If you use omeprazole for a long period, your healthcare professional may review your treatment regularly. Some risks, including certain side effects and changes such as fundic gland polyps, may be more relevant with prolonged use.
Long-Term Risks of Omeprazole
For many patients, long-term omeprazole remains appropriate because the benefits outweigh the risks. However, prolonged use should be reviewed periodically to ensure the medicine is still needed and that the lowest effective dose is being used.
Vitamin B12 Deficiency
Reducing stomach acid for long periods can decrease vitamin B12 absorption.
Possible symptoms include:
- Persistent tiredness
- Tingling or numbness
- Memory problems
- Weakness
- Difficulty concentrating
Your healthcare professional may recommend testing if you have symptoms or have been taking omeprazole for an extended period.
Low Magnesium Levels
Low magnesium (hypomagnesaemia) may occur, particularly after several months of treatment.
Symptoms can include:
- Muscle cramps
- Tremors
- Fatigue
- Dizziness
- Irregular heartbeat
If you require long-term treatment, your clinician may recommend blood tests where appropriate.
Bone Health
Long-term proton pump inhibitor use has been associated with a small increased risk of fractures, particularly in older adults and those with osteoporosis.
This does not mean everyone taking omeprazole will develop bone problems, but maintaining adequate calcium and vitamin D intake, together with regular medication reviews, is important for people at higher risk.
Gastrointestinal Infections
Reducing stomach acid may slightly increase susceptibility to certain infections because stomach acid normally helps destroy harmful bacteria.
Examples include:
- Clostridioides difficile infection
- Some food-borne gastrointestinal infections
Although the overall risk remains low,seek medical advice if you develop severe or persistent diarrhoea or significant abdominal pain while taking omeprazole .
Can You Take Expired Omeprazole?
People often search for information about expired omeprazole after finding unused capsules or tablets at home.
It is generally recommended not to take medicines after their expiry date. Over time, medicines may lose their effectiveness, and their quality and safety cannot be guaranteed after the expiry date shown on the packaging.
If your omeprazole has expired:
- Do not take it without advice from a healthcare professional.
- Arrange a new supply if you still need treatment.
- Return expired medicines to your local pharmacy for safe disposal.
- Do not throw medicines into household waste or wastewater unless you have been advised to do so.
Omeprazole Patient Information Leaflet: Key Safety Points
Every pack of omeprazole includes a Patient Information Leaflet (PIL), which should be read before starting treatment and may also outline dosage forms such as a delayed-release capsule, delayed release tablet, or oral suspension where relevant.
The leaflet explains:
- What omeprazole is used for
- Who should not take it
- How to take it correctly, including when to swallow certain delayed-release capsules or delayed-release tablets whole, or mix some granules with cool water if directed
- Possible side effects
- Drug interactions
- Pregnancy and breastfeeding advice
- Storage instructions
- When to seek urgent medical attention
If you misplace the leaflet, an electronic version is usually available through the electronic Medicines Compendium (eMC) or the manufacturer's website .
NHS Safety Advice for Omeprazole
The NHS guidance says that omeprazole is generally safe when used correctly, but patients should be aware of several important points:
- Use the lowest effective dose for the shortest appropriate duration.
- Long-term treatment should be reviewed regularly to ensure it remains appropriate .
- Tell your healthcare professional about all other medicines you take.
- Do not ignore persistent or worsening symptoms.
- Seek urgent medical advice if you experience symptoms of a serious allergic reaction or severe side effects.
These recommendations help ensure that treatment remains both safe and effective.
