The content on this page is not medical advice and should be used for informational purposes only. Always consult your health care provider or pharmacist to determine what medication and dosage are right for you.

Reviewed by

Kristina Woodworth

Last updatedFebruary 23, 2023

Omeprazole

For treating gastroesophageal reflux disease (GERD) and damage caused by GERD.

It is also taken for ulcers in the stomach or small intestine, or to treat too much stomach acid.

An over-the-counter version is available to treat frequent heartburn in adults.

Brand name

Prilosec, Prilosec OTC, Talicia (containing omeprazole, amoxicillin, rifabutin), Zegerid, Zegerid OTC (containing omeprazole and sodium bicarbonate)

Rx or OTC

By prescription and over-the-counter

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When & How

Prescription omeprazole is a delayed-release medication that is usually taken once a day, at least one hour before a meal, for GERD.
Swallow capsules or tablets whole, and drink a full glass of water.
Prescription omeprazole is taken twice a day to eliminate an H. pylori infection. It is typically prescribed in a combination pill that contains bismuth and antibiotics.
Prescription omeprazole may be taken 3 times a day for excess acid production.
Granule formulation should be mixed with liquid to take by mouth or through a feeding tube.
Over-the-counter (OTC) omeprazole is usually taken once a day in the morning at least one hour before eating, for 14 days in a row. If needed, this 14-day treatment may be repeated, but not more than once every 4 months.

Do’s

Take omeprazole exactly as prescribed by your doctor. If taking the OTC version, follow the directions on the package.
Take prescription omeprazole at the same time every day to help remember your dose.
If you have trouble swallowing capsules, place one tablespoon of soft, cool applesauce in an empty bowl; open the capsule and carefully empty all the granules onto the applesauce; mix and immediately swallow the applesauce with a cool glass of water. Do not save the granule/applesauce mixture for future use.

Don’ts

Do not split, chew, or crush delayed-release capsules or tablets.
Do not rely on OTC omeprazole for the immediate relief of heartburn symptoms as it may take 1 to 4 days for your symptoms to improve.
Do not stop taking prescription omeprazole without talking to your doctor.

Discuss with your doctor

If you are taking OTC omeprazole and your symptoms get worse or do not improve after 14 days, or if your symptoms return sooner than 4 months after a 14-day treatment
If your condition does not improve or gets worse while taking prescription omeprazole
If you know that you are allergic to omeprazole, dexlansoprazole (Dexilant), esomeprazole (Nexium), lansoprazole (Prevacid, in Prevpac), pantoprazole (Protonix), rabeprazole (Aciphex), any other medications
Any other prescription drugs you are taking
If you are taking rilpivirine (Edurant, in Complera, Odefsey), your doctor will probably tell you not to take omeprazole, or may change the doses of other medications, or monitor you closely for side effects.
Any OTC medications, vitamins, nutritional supplements, or herbal products you are currently taking
If you are of Asian descent (you may metabolize the drug differently and have a risk of higher levels of it in your blood)
If you have or have ever had a low level of magnesium or vitamin B-12 in your blood
If you have osteoporosis
If you have or have ever had an autoimmune disease such as systemic lupus erythematosus
If you have or have ever had liver disease
If you are pregnant, breastfeeding, or plan to be pregnant. You should not take omeprazole while breastfeeding as it can pass into breast milk and may harm your baby.

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What is Omeprazole?

Omeprazole is a proton-pump inhibitor used to treat GERD, which causes acid to move up from the stomach to the esophagus. Omeprazole can also treat damage to the esophagus caused by GERD, allowing the esophagus to heal.

It may be taken for ulcers in the stomach or small intestine, and to prevent the return of ulcers from infection by the bacteria, Helicobacter pylori, in adults. It also is taken in people with too much stomach acid.

Omeprazole works by decreasing the amount of acid produced by the stomach.

Over-the-counter omeprazole is taken for frequent heartburn (occurring at least 2 or more days a week) in adults.

Omeprazole is available by prescription and over-the-counter.

Omeprazole dosages

Capsules and granules

10 mg capsule
20 mg capsule (Rx & OTC)
40 mg capsule
2.5 mg or 10 mg granule packets for oral suspension

Similar drugs to Omeprazole

Prevacid (lansoprazole)
Nexium (esomeprazole)
Dexilant (dexlansoprazole)
Aciphex (rabeprazole)
Protonix (pantoprazole

Side effects

Disclaimer

Medications may affect individuals differently. Usage of any medication may include side effects and other interactions. Here is a list of known common side effects and interactions. This list is not exhaustive -- there may be other side effects or interactions for this medication that are not listed here. In some cases, the likelihood of side effects or interactions may increase depending on dosage. It’s important to keep in mind that in extreme cases, other serious side effects, even death, may occur. Always consult your health care provider or pharmacist to determine what medication and dosage is right for you.

Headache

7% of people experience headache

Abdominal pain

5% of people experience abdominal pain

Nausea

4% of people experience nausea

Diarrhea

4% of people experience diarrhea

Vomiting

3% of people experience vomiting

Gas

3% of people experience gas

Full list of side effects

Headache
Dizziness
Weakness, lack of energy
Back pain
Abdominal pain
Nausea
Diarrhea
Vomiting
Gas
Acid regurgitation
Constipation
Upper respiratory infection
Cough
Rash
C. difficile associated diarrhea
Osteoporosis-related fractures of the hip, wrist, or spine
Irregular or fast heartbeat

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Long-term complications

Long-term use may cause atrophic gastritis (inflammation of the stomach lining)
Long-term and multiple daily doses can increase the risk of osteoporosis-related fractures of the hip, wrist, or spine.
Low magnesium levels, with or without symptoms

Safety notes

Hypersensitivity reactions can occur including anaphylaxis, anaphylactic shock, angioedema, bronchospasm, interstitial nephritis, urticaria, fever; pain; fatigue; malaise
It’s important to know that cancer cannot be ruled out just because your symptoms respond to omeprazole treatment.
Treatment with proton-pump inhibitors like omeprazole can increase the risk of Clostridium difficile infection, especially if you are hospitalized. C. difficile diagnosis should be considered for diarrhea that does not improve while taking omeprazole.
Low magnesium levels have been rarely reported with more than 3 months of treatment with proton-pump inhibitors like omeprazole, in most cases after a year of treatment. This can cause serious effects such as seizures, arrhythmias, or muscle spasms.

What else you should know

Taking omeprazole may cause a false-positive result if you are being evaluated for a neuroendocrine tumor.

Omeprazole interactions

Disclaimer

Tell your doctor if you are taking any of these medications or supplements

Omeprazole taken with clopidogrel can lower the activity of clopidogrel, so avoid taking these drugs together.
Taking omeprazole with methotrexate may result in high levels of methotrexate or methotrexate toxicity. Your doctor may temporarily stop omeprazole treatment if you are taking a high dose of methotrexate.
Taking St. John’s Wort, an herbal therapy, with omeprazole can reduce the concentration of omeprazole.
Omeprazole reduces levels of atazanavir and nelfinavir; use with omeprazole is not recommended
Omeprazole increases levels of saquinavir; your doctor may monitor for toxicity and consider dose reduction of saquinavir.
Omeprazole may interfere with drugs that are affected by stomach acid including ketoconazole, iron salts, ampicillin esters, and digoxin; your doctor may monitor for digoxin toxicity.

Tell your doctor if you have any of these pre-existing conditions

Liver disease; your doctor may consider a reduction in omeprazole dose, especially if you are taking it to heal the esophagus.
If you are pregnant, breastfeeding, or plan to be pregnant.

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