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Omeprazole 10 mg, 20 mg and 40 mg – patient leaflet, side effects, dosage

Status:
Prescription only (POM) Key facts
Medicine strength:
40 mg
Contains active substance:
ATC code:

Patient leaflet - Omeprazole 40 mg capsules

1. What Omeprazole is and what it is used for

2. What you need to know before you take

Omeprazole

  1. 3. How to take Omeprazole
  2. 4. Possible side effects
  3. 5. How to store Omeprazole
  4. 6.

    1 WHAT OMEPRAZOLE IS AND WHAT

    IT IS USED FOR

Omeprazole contains the active substance omeprazole. It belongs to a group of medicines called ‘proton pump inhibitors’. They work by reducing the amount of acid that your stomach produces.

Omeprazole is used to treat the following conditions:

Adults

  • ‘Gastro-esophageal reflux disease’ (GORD). This

    is where acid from the stomach escapes into the gullet (the tube which connects your throat to your stomach) causing pain, inflammation and heartburn.

  • Ulcers in the upper part of the intestine (duodenal

    ulcers) or stomach (gastric ulcer).

  • Ulcers which are infected with bacteria called

    ‘Helicobacter pylori’. If you have this condition, your doctor may also prescribe antibiotics to treat the infection and allow the ulcer to heal.

  • Ulcers caused by medicines called NSAIDs (Non-

    Steroidal Anti-Inflammatory Drugs). Omeprazole can also be used to stop ulcers from forming if you are taking NSAIDs.

  • Too much acid in the stomach caused by

    a growth in the pancreas (Zollinger-Ellison syndrome).

Children and adolescents

Children over 1 year of age and ≥ 10 kg

  • ‘Gastro-oesophageal reflux disease’ (GORD).

    This is where acid from the stomach escapes into the gullet (the tube which connects your throat to your stomach) causing pain, inflammation and heartburn.

    In children, the symptoms of the condition can

    include the return of stomach contents into the mouth (regurgitation), being sick (vomiting) and poor weight gain.

Children over 4 years of age and adolescents

  • Ulcers which are infected with bacteria called

    ‘Helicobacter pylori’. If your child has this condition, your doctor may also prescribe antibiotics to treat the infection and allow the ulcer to heal.

    2 WHAT YOU NEED TO KNOW

    BEFORE YOU TAKE OMEPRAZOLE

Do not take Omeprazole

  • If you are allergic to omeprazole or any of the other

    ingredients of this medicine (listed in section 6).

  • If you are allergic to medicines containing other

    proton pump inhibitors (e.g. pantoprazole, lansoprazole, rabeprazole, esomeprazole).

  • If you are taking a medicine containing nelfinavir

    (used for HIV infection)

Do not take Omeprazole if any of the above applies to you. If you are not sure, talk to your doctor or pharmacist before taking Omeprazole.

Warnings and precautions

Talk to your doctor or pharmacist before taking Omeprazole.

Serious skin reactions including Stevens-Johnson syndrome, toxic epidermal necrolysis, drug reaction with eosinophilia and systemic symptoms (DRESS) and acute generalized exanthematous pustulosis (AGEP) have been reported in association with Omeprazole treatment. Stop using Omeprazole and seek medical attention immediately if you notice any of the symptoms related to these serious skin reactions described in section 4.

Omeprazole may hide the symptoms of other diseases. Therefore, if any of the following happen to you before you start taking Omeprazole or while you are taking it, talk to your doctor straight away:

  • You lose a lot of weight for no reason and have

    problems swallowing.

  • You get stomach pain or indigestion.
  • You begin to vomit food or blood.
  • You pass black stools (blood-stained faeces).
  • You experience severe or persistent diarrhoea,

    as omeprazole has been associated with a small increase in infectious diarrhoea.

  • You have severe liver problems.
  • You are due to have a specific blood test

    (Chromogranin A).

  • You have ever had a skin reaction after treatment

    with a medicine similar to Omeprazole that reduces stomach acid.

If you take Omeprazole on a long-term basis (longer than 1 year) your doctor will probably keep you under regular surveillance. You should report any new and exceptional symptoms and circumstances whenever you see your doctor.

When taking omeprazole, inflammation in your kidney may occur. Signs and symptoms may include decreased volume of urine or blood in your urine and/or hypersensitivity reactions such as fever, rash, and joint stiffness. You should report such signs to the treating physician.

Taking a proton pump inhibitor like omeprazole, especially over a period of more than one year, may slightly increase your risk of fracture in the hip, wrist or spine. Tell your doctor if you have osteoporosis or if you are taking corticosteroids (which can increase the risk of osteoporosis).

If you get a rash on your skin, especially in areas exposed to the sun tell your doctor as soon as you can, as you may need to stop your treatment with Omeprazole. Remember to also mention any other ill-effects like pain in your joints.

This medicine may affect the way that your body absorbs vitamin B12, particularly if you need to take it for a long time. Please contact your doctor if you notice any of the following symptoms, which could indicate low levels of vitamin B12:

  • Extreme tiredness or lack of energy
  • Pins and needles
  • Sore or red tongue, mouth ulcers
  • Muscle weakness
  • Disturbed vision
  • Problems with memory, confusion, depression

    Children

    Some children with chronic illnesses may require long-term treatment although it is not recommended. Do not give this medicine to children under 1 year of age or < 10 kg.

    Other medicines and Omeprazole

    Tell your doctor or pharmacist if you are taking, have recently taken or might take any other medicines. This includes medicines that you buy without a prescription. This is because Omeprazole can affect the way some medicines work and some medicines can have an effect on Omeprazole.

    Do not take Omeprazole if you are taking a medicine containing nelfinavir (used to treat HIV infection).

    Tell your doctor or pharmacist if you are taking any of the following medicines:

    • Ketoconazole, itraconazole, posaconazole or voriconazole (used to treat infections caused by a fungus).
    • Digoxin (used to treat heart problems).
    • Diazepam (used to treat anxiety, relax muscles or in epilepsy).
    • Phenytoin (used in epilepsy). If you are taking phenytoin, your doctor will need to monitor you when you start or stop taking Omeprazole.
    • Medicines that are used to thin your blood, such as warfarin or other vitamin K blockers. Your doctor may need to monitor you when you start or stop taking Omeprazole.
    • Rifampicin (used to treat tuberculosis).
    • Atazanavir (used to treat HIV infection).
    • Tacrolimus (in cases of organ transplantation).
    • St John’s wort (Hypericum perforatum) (used to treat mild depression).
    • Cilostazol (used to treat intermittent claudication).
    • Saquinavir (used to treat HIV infection).
    • Clopidogrel (used to prevent blood clots

      (thrombi)).

    • Erlotinib (used to treat cancer)
    • Methotrexate (a chemotherapy medicine used in high doses to treat cancer) – if you are taking a high dose of methotrexate, your doctor may temporarily stop your Omeprazole treatment

If your doctor has prescribed the antibiotics amoxicillin and clarithromycin as well as Omeprazole to treat ulcers caused by Helicobacter pylori infection, it is very important that you tell your doctor about any other medicines you are taking.

Omeprazole with food and drink

You can take your capsules with food or on an empty stomach.

Pregnancy and breast-feeding

If you are pregnant or breast-feeding, think you may be pregnant or are planning to have a baby, ask your doctor or pharmacist for advice before taking this medicine.

Omeprazole is excreted in breast milk but is not likely to influence the child when therapeutic doses are used.

Your doctor will decide whether you can take Omeprazole if you are breast-feeding.

Driving and using machines

Omeprazole is not likely to affect your ability to drive or use any tools or machines. Side effects such as dizziness and visual disturbances may occur (see section 4).

If affected, you should not drive or operate machinery.

Omeprazole contains sucrose and sodium

If you have been told by your doctor that you have an intolerance to some sugars, contact your doctor before taking this medicine.

This medicine contains less than 1 mmol (23 mg) sodium per gastro-resistant hard capsule, that is to say essentially ‘sodium-free’.

3 HOW TO TAKE OMEPRAZOLE

Always take this medicine exactly as your doctor or pharmacist has told you. Check with your doctor or pharmacist if you are not sure.

Your doctor will tell you how many capsules to take and how long to take them for. This will depend on your condition and how old you are.

The recommended dose is:

Adults

To treat symptoms of GORD such as heartburn and acid regurgitation:

  • If your doctor has found that your food

    pipe (gullet) has been slightly damaged, the recommended dose is 20 mg once a day for 4-8 weeks. Your doctor may tell you to take a dose of 40 mg for a further 8 weeks if your gullet has not yet healed.

  • The recommended dose once the gullet has healed is 10 mg once a day.
  • If your gullet has not been damaged, the

    recommended dose is 10 mg once a day.

To treat ulcers in the upper part of the intestine (duodenal ulcer):

  • The recommended dose is 20 mg once a day for 2 weeks. Your doctor may tell you to take the same dose for a further 2 weeks if your ulcer has not yet healed.
  • If the ulcers do not fully heal, the dose can be increased to 40 mg once a day for 4 weeks.

To treat ulcers in the stomach (gastric ulcer):

  • The recommended dose is 20 mg once a day for 4 weeks. Your doctor may tell you to take the same dose for a further 4 weeks if your ulcer has not yet healed.
  • If the ulcers do not fully heal, the dose can be increased to 40 mg once a day for 8 weeks.

To prevent the duodenal and stomach ulcers from coming back:

  • The recommended dose is 10 mg or 20 mg once a day. Your doctor may increase the dose to 40 mg once a day.

To treat duodenal and stomach ulcers caused by NSAIDs (Non-Steroidal Anti-Inflammatory Drugs):

  • The recommended dose is 20 mg once a day for

    4–8 weeks.

To prevent duodenal and stomach ulcers if you are taking NSAIDs:

  • The recommended dose is 20 mg once a day.

To treat ulcers caused by Helicobacter pylori infection and to stop them coming back:

  • The recommended dose is 20 mg Omeprazole twice a day for one week.
  • Your doctor will also tell you to take two

    antibiotics among amoxicillin, clarithromycin and metronidazole.

To treat too much acid in the stomach caused by a growth in the pancreas (Zollinger-Ellison syndrome):

  • The recommended dose is 60 mg daily.
  • Your doctor will adjust the dose depending on your needs and will also decide how long you need to take the medicine for.

Use in children and adolescents

To treat symptoms of GORD such as heartburn and acid regurgitation:

  • Children over 1 year of age and with a body weight of more than 10 kg may take Omeprazole. The dose for children is based on the child’s weight and the doctor will decide the correct dose.

    Continued on the next page >> To treat ulcers caused by Helicobacter pylori infection and to stop them coming back:

  • Children aged over 4 years may take Omeprazole.

    The dose for children is based on the child’s weight and the doctor will decide the correct dose.

  • Your doctor will also prescribe two antibiotics

    called amoxicillin and clarithromycin for your child.

Taking this medicine

  • It is recommended that you take your capsules in

    the morning.

  • You can take your capsules with food or on an

    empty stomach.

  • Swallow your capsules whole with half a glass of

    water. Do not chew or crush the capsules. This is because the capsules contain coated pellets which stop the medicine from being broken down by the acid in your stomach. It is important not to damage the pellets.

What to do if you or your child have trouble swallowing the capsules

  • If you or your child have trouble swallowing the

    capsules:

    • Open the capsules and swallow the contents

      directly with half a glass of water or put the contents into a glass of still (non-fizzy) water, any acidic fruit juice (e.g. apple, orange or pineapple) or apple sauce.

    • Always stir the mixture just before drinking it

      (the mixture will not be clear). Then drink the mixture straight away or within 30 minutes.

    • To make sure that you have drunk all of the

      medicine, rinse the glass very well with half a glass of water and drink it. The solid pieces contain the medicine - do not chew or crush them.

If you take more Omeprazole than you should

If you take more Omeprazole than prescribed by your doctor, talk to your doctor or pharmacist straight away.

If you forget to take Omeprazole

If you forget to take a dose, take it as soon as you remember it. However, if it is almost time for your next dose, skip the missed dose. Do not take a double dose to make up for a forgotten dose.

If you stop taking Omeprazole

Do not stop taking Omeprazole without first talking to your doctor or pharmacist.

If you have any further questions on the use of this medicine, ask your doctor or pharmacist.

4 POSSIBLE SIDE EFFECTS

Like all medicines, this medicine can cause side effects, although not everybody gets them.

If you notice any of the following rare (may affect up to 1 in 1,000 people) or very rare (may affect up to 1 in 10,000 people) but serious side effects, stop taking Omeprazole and contact a doctor immediately:

  • Sudden wheezing, swelling of your lips, tongue

    and throat or body, rash, fainting or difficulties in swallowing (severe allergic reaction). (rare)

  • Reddening of the skin with blisters or peeling.

    There may also be severe blisters and bleeding in the lips, eyes, mouth, nose and genitals. This could be ‘Stevens-Johnson syndrome’ or ‘toxic epidermal necrolysis’. (very rare)

  • Widespread rash, high body temperature and

    enlarged lymph nodes (DRESS syndrome or drug hypersensitivity syndrome). (rare)

  • A red, scaly widespread rash with bumps under

    the skin and blisters accompanied by fever. The symptoms usually appear at the initiation of treatment (acute generalized exanthematous pustulosis). (rare)

  • Yellow skin, dark urine and tiredness which can

    be symptoms of liver problems.

Other side effects include:

Common side effects (may affect up to 1 in 10 people)

  • Headache
  • Effects on your stomach or gut: diarrhoea,

    stomach pain, constipation, wind (flatulence)

  • Feeling sick (nausea) or being sick (vomiting).
  • Benign polyps in the stomach.

Uncommon side effects (may affect up to 1 in 100 people)

  • Swelling of the feet and ankles
  • Disturbed sleep (insomnia)
  • Dizziness, tingling feelings such as “pins and

    needles”, feeling sleepy

  • Spinning feeling (vertigo)
  • Changes in blood tests that check how the liver is

    working

  • Skin rash, lumpy rash (hives) and itchy skin
  • Generally feeling unwell and lacking energy
  • Fracture in the hip, wrist or spine.

Rare side effects (may affect up to 1 in 1,000 people)

  • Blood problems such as a reduced number of

    white cells or platelets. This can cause weakness, bruising or make infections more likely

  • Low levels of sodium in the blood. This may

    cause weakness, being sick (vomiting) and cramps

  • Feeling agitated, confused or depressed
  • Taste changes
  • Eyesight problems such as blurred vision
  • Suddenly feeling wheezy or short of breath

    (bronchospasm)

  • Dry mouth
  • An inflammation of the inside of the mouth
  • An infection called “thrush” which can affect the

    gut and is caused by a fungus

  • Hair loss (alopecia)
  • Skin rash on exposure to sunshine
  • Joint pains (arthralgia) or muscle pains (myalgia)
  • Severe kidney problems (interstitial nephritis)
  • Increased sweating.

Very rare side effects (may affect up to 1 in 10,000 people)

  • Changes in blood count including agranulocytosis

    (lack of white blood cells)

  • Aggression
  • Seeing, feeling or hearing things that are not there

    (hallucinations)

  • Severe liver problems leading to liver failure and

    inflammation of the brain

  • Erythema multiforme
  • Muscle weakness
  • Enlarged breasts in men

Not known (frequency cannot be estimated from the available data)

  • Inflammation in the gut (leading to diarrhoea).
  • If you are on Omeprazole for more than three

    months it is possible that the levels of magnesium in your blood may fall. Low levels of magnesium can be seen as fatigue, involuntary muscle contractions, disorientation, convulsions, dizziness or increased heart rate. If you get any of these symptoms, please tell your doctor promptly. Low levels of magnesium can also lead to a reduction in potassium or calcium levels in the blood. Your doctor may decide to perform regular blood tests to monitor your levels of magnesium.

  • Rash, possibly with pain in the joints.

Omeprazole may in very rare cases affect the white blood cells leading to immune deficiency. If you have an infection with symptoms such as fever with a severely reduced general condition or fever with symptoms of a local infection such as pain in the neck, throat or mouth or difficulties in urinating, you must consult your doctor as soon as possible so that a lack of white blood cells (agranulocytosis) can be ruled out by a blood test. It is important for you to give information about your medicine at this time.

Reporting of side effects

If you get any side effects, talk to your doctor or pharmacist. This includes any possible side effects not listed in this leaflet. You can also report side effects directly via the Yellow Card Scheme (www.mhra.gov.uk/yellowcard) or search for MHRA Yellow Card in Google play or Apple App store. By reporting side effects you can help provide more information on the safety of this medicine.

5 HOW TO STORE OMEPRAZOLE

Keep this medicine out of the sight and reach of children.

Do not use this medicine after the expiry date which is stated on the carton or blister/bottle after “EXP”. The expiry date refers to the last day of that month.

For blister:

Do not store above 25ºC.

Store in the original package in order to protect from light and moisture.

For bottle:

Do not store above 25°C.

Keep the bottle tightly closed in order to protect from light and moisture.

In-use shelf life after first opening of the bottle: 100 days.

Do not throw away any medicines via wastewater or household waste. Ask your pharmacist how to throw away medicines you no longer use. These measures will help protect the environment.

6 CONTENTS OF THE PACK AND

OTHER INFORMATION

What Omeprazole contains

The active substance is omeprazole.

Each gastro-resistant capsule, hard contains 10 mg, 20 mg, 40 mg of omeprazole.

Omeprazole 10 mg Capsules:

The other ingredients are: capsule contents: sugar spheres (contain sucrose and maize starch), hypromellose, sodium lauryl sulfate, povidone K25, talc, magnesium oxide heavy, methacrylic acid - ethyl acrylate copolymer 1:1 (dispersion 30%), triethyl citrate; capsule shell: gelatine, titanium dioxide (E171), yellow iron oxide (E172), red iron oxide (E172), may also contain black iron oxide (E172).

Omeprazole 20 mg Capsules:

The other ingredients are: capsule contents: sugar spheres (contain sucrose and maize starch), hypromellose, sodium lauryl sulfate, povidone K25, talc, magnesium oxide heavy, methacrylic acid - ethyl acrylate copolymer 1:1 (dispersion 30%), triethyl citrate; capsule shell: gelatine, titanium dioxide (E171).

Omeprazole 40 mg Capsules:

The other ingredients are: capsule contents: sugar spheres (contain sucrose and maize starch), hypromellose, sodium lauryl sulfate, povidone K25, talc, magnesium oxide heavy, methylacrylic acid - ethyl acrylate copolymer 1:1 (dispersion 30%), triethyl citrate; capsule shell: gelatine, titanium dioxide (E171), yellow iron oxide (E172), red iron oxide (E172), may also contain black iron oxide (E172).

What Omeprazole Capsules look like and contents of the pack

Omeprazole 10 mg:

Hard gelatin capsules with light brown cap and light brown body, containing almost white to light brown pellets.

Omeprazole 20 mg:

Hard gelatin capsules with white cap and white body, containing almost white to light brown pellets.

Omeprazole 40 mg:

Hard gelatin capsules with white cap and light brown body, containing almost white to light brown pellets.

Omeprazole 10 mg:

Aluminium/Aluminium blister or PVC/PE/PVDC-Alu blister or PVC/PVDC- Alu blister in packs of 7, 14, 15, 28, 30, 56, 56x1 and 98 gastro-resistant capsules, hard.

White HDPE bottles with inserted desiccant (silica gel capsule) with PP screw cap: boxes containing 1 bottle of 7, 14, 15, 28, 30, 49, 50, 56, 60, 98, 100 and 168 gastro-resistant capsules, hard or boxes containing 2 bottles of 28, 49, 50 and 168 gastro-resistant capsules, hard.

Omeprazole 20 mg:

Aluminium/Aluminium blister or PVC/PE/PVDC-Alu blister or PVC/PVDC- Alu blister in packs of 7, 14, 15, 28, 30, 56, 56x1 and 98 gastro-resistant capsules, hard.

White HDPE bottles with inserted desiccant (silica gel capsule) with PP screw cap: boxes containing 1 bottle of 7, 14, 15, 28, 30, 49, 50, 56, 60, 98, 100 and 168 gastro-resistant capsules, hard or boxes containing 2 bottles of 28, 30, 49, 50 and 168 gastro-resistant capsules, hard.

Omeprazole 40 mg:

Aluminium/Aluminium blister or PVC/PE/PVDC-Alu blister or PVC/PVDC- Alu blister in packs of 7, 14, 15, 28, 30, 56 and 98 gastro-resistant capsules, hard.

White HDPE bottles with inserted desiccant (silica gel capsule) with PP screw cap: boxes containing 1 bottle of 7, 14, 15, 28, 30, 49, 50, 56, 60, 98, 100 and 168 gastro-resistant capsules, hard or boxes containing 2 bottles of 28, 30, 49, 50 and 168 gastro-resistant capsules, hard.

Not all pack sizes may be marketed.

Marketing Authorisation Holder and Manufacturer

Marketing authorisation holder:

Sandoz Limited

Park View, Riverside Way

Watchmoor Park

Camberley, Surrey

GU15 3YL

United Kingdom

Manufacturer:

Lek Pharmaceuticals d.d.

Verovškova 57,

1526 Ljubljana

Slovenia

Salutas Pharma GmbH

Otto-von-Guericke-Allee 1

39179 Barleben

Germany

LEK S.A.

ul. Domaniewska 50 C

02-672 Warszawa

Poland

Sandoz S.R.L.

Str. Livezeni nr. 7A

RO-540472 Targu-Mures

Romania

LEK Pharmaceuticals d.d.

Trimlini 2D

9220 Lendava, Slovenia

Lek S.A.,

Ul. Podlipie 16,

95-010 Strykow,

Poland

Variation:V106 – Addition of alternative forming foilTechnical Colours:
040.0Legend:
Date prepared:02/03/2026Cutting:
8.5 pt
Helvetica
165x620 mm
Technical data:
SKUs:N/A
SZ codes:SZ00000LT000
N/AColours:
N/A

About this document

Source: MHRA - Medicines and Healthcare products Regulatory Agency (products.mhra.gov.uk) · Marketing authorisation: PL 04416/0653

MHRA data as of 13 October 2026

What the sections and the side effect frequencies mean: How to read a patient leaflet

Found a mistake? Tell us on the contact page.

The information on this site does not replace the advice of a doctor or pharmacist.

Facts about Omeprazole 40 mg capsules

What these facts mean

Prescription needed?? Yes, prescription-only medicine (POM)
Active substance? Omeprazole
Strength? 40 mg
Pharmaceutical form? Gastro-resistant capsule
Hard gelatin capsules with white cap and light brown body, containing almost white to light brown pellets.
How is it taken? Oral
Excipients? Sugar spheres (contain sucrose and maize starch), Hypromellose, Sodium lauryl sulfate, Magnesium oxide heavy, Povidone K25, Talc, Methacrylic acid ethyl acrylate copolymer 1:1 (dispersion 30%), Triethyl citrate, Gelatin, Titanium dioxide (E171), Red iron oxide (E172), Yellow iron oxide (E172), May also contain: Black iron oxide (E172)
Pack sizes 28 capsule
Is it available?? Listed as available (NHS Dictionary of Medicines and Devices – not a record of current supplies)
Shelf life? 2 years
For bottle:
In – use shelf life after first opening: 100 days.
Do not store above 25°C. Keep the bottle tightly closed in order to protect from light and moisture.
Storage Do not store above 25°C.
For blister: Store in the original package in order to protect from light and moisture.
For bottle: Keep the bottle tightly closed in order to protect from light and moisture.
For storage conditions after first opening of the medicinal product, see section 6.3.
Drug group (ATC)? Drugs for acid related disorders, drugs for peptic ulcer and gastro-oesophageal reflux disease (GORD), proton pump inhibitors
  1. A Alimentary tract and metabolism drugs
    1. A02 Drugs for acid related disorders
      1. A02B Drugs for peptic ulcer and gastro-oesophageal reflux disease (GORD)
        1. A02BC Proton pump inhibitors for peptic ulcer and GORD
          1. A02BC01 omeprazole
Marketing authorisation? PL 04416/0653 (first authorised 4 March 2005)
Marketing authorisation holder? Sandoz Limited
Codes? GTIN 7613421046521 · BNF 01030500

Sources: the MHRA product information (products.mhra.gov.uk) and the NHS Dictionary of Medicines and Devices (dm+d), release 11.1.0 of 9 November 2026, NHS Business Services Authority. Contains public sector information licensed under the Open Government Licence v3.0.