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Overview: Omeprazole is used for heartburn, acid reflux, and other conditions where you have too much acid in your stomach. It works by reducing how much acid your stomach makes and usually takes a few days to fully work. Common side effects include headache, stomach pain, nausea, diarrhea, and gas. Other side effects are possible, especially if this medicine is taken long term. Contact your health care provider right away if you are peeing less than usual, have watery diarrhea that does not go away, a skin rash, dizziness, or unusual joint pain.

Uses

What is omeprazole used for?

Omeprazole is used to treat heartburn and certain other conditions caused by too much acid in the stomach.

Gastroesophageal reflux disease (GERD), where stomach acid backs up into your esophagus

Omeprazole may also be used for other conditions as determined by your health care provider.

How does omeprazole work (mechanism of action)?

Omeprazole works by decreasing the amount of acid your stomach makes.

How is omeprazole supplied (dosage forms)?

Brands and other names

  • Prilosec
  • Prilosec OTC

Dosage forms and strengths

  • 10 mg, 20 mg, 40 mg delayed-release oral capsules
  • 20 mg delayed-release oral tablets
  • 20 mg delayed-release orally disintegrating tablets
  • 2.5 mg, 10 mg packets of powder (delayed-release granules) for oral suspension

How should I store omeprazole?

Omeprazole should be stored at room temperature, between 68 F and 77 F (20 C and 25 C). It can be exposed to temperatures between 59 F and 86 F (15 C and 30 C), for shorter periods of time, such as when transporting it. Store in a cool, dry place.

Do not remove orally disintegrating tablets from the blister pack until ready to take. 

Side Effects

What are the most common side effects of omeprazole?

The most common side effects of omeprazole are listed below. Tell your health care provider if you have any of these side effects that bother you.

  • Headache
  • Stomach pain
  • Nausea
  • Diarrhea
  • Vomiting
  • Gas
  • Infection in the nose or throat (children age 1 to 16 years)
  • Fever (children age 1 to 16 years)

There may be other side effects of omeprazole that are not listed here. Contact your health care provider if you think you are having a side effect of a medicine. In the U.S., you can report side effects to the FDA at www.fda.gov/medwatch or by calling 800-FDA-1088. In Canada, you can report side effects to Health Canada at www.health.gc.ca/medeffect or by calling 866-234-2345.

What are the serious side effects of omeprazole?

While less common, the most serious side effects of omeprazole are described below, along with what to do if they happen.

Kidney Problems. A type of kidney problem called acute tubulointerstitial nephritis can happen at any time during treatment with omeprazole. If you notice a decrease in the amount of your urine or see blood in your urine, call your health care provider right away. 

Antibiotic-Related Diarrhea. An overgrowth of germs called Clostridioides difficile, or “C. diff,” can happen in your gut during treatment with omeprazole. Call your health care provider right away if you have any of the following symptoms of this condition.

  • Watery diarrhea
  • Diarrhea that does not go away
  • Blood in your stool (poop)
  • Severe stomach cramps
  • Fever that starts after you start or finish the medicine

Severe Skin Reactions. Omeprazole can cause severe skin reactions, such as Stevens-Johnson Syndrome (SJS) and Toxic Epidermal Necrolysis (TEN), that can lead to death if not treated. If you get a rash, stop using omeprazole and call your health care provider right away. Get emergency help if you have any of the following symptoms of SJS or TEN.

  • Painful skin that looks burned and peels off
  • Flat rash or blisters on your skin, mouth, nose, and genitals
  • Red, painful, watery eyes
  • Flu-like symptoms including fever, chills, and muscle aches

Severe Allergic Reaction called DRESS. Omeprazole can cause a specific type of allergic reaction called DRESS. DRESS stands for Drug Reaction with Eosinophilia and Systemic Symptoms. It is also sometimes called multi-organ hypersensitivity. This is a reaction that can affect multiple parts of the body including your liver, kidneys, and heart. Stop using the medicine and get help right away if you have any of the following symptoms of this serious reaction.

  • Breathing problems or wheezing
  • Racing heart
  • Itching or skin rash
  • Bumps on the skin called hives that can be red, pink, white, or brown depending on your skin tone
  • Fever or general ill feeling
  • Swollen lymph nodes
  • Swelling of the face, lips, mouth, tongue, or throat
  • Shortness of breath, trouble swallowing, or throat tightness
  • Swelling in your feet, ankles, or legs
  • Nausea or vomiting
  • Dizziness, feeling lightheaded, or fainting
  • Stomach cramps
  • Joint pain
  • Dark-colored pee
  • Your skin or the whites of your eyes turning yellowish in color (also called jaundice)

Lupus. Some medicines, such as omeprazole, can cause certain types of lupus or cause worsening of lupus you already have. Lupus is an autoimmune disorder where your immune cells attack other cells or organs in your body. Tell your provider right away if you have new or worsening joint pain or a rash on your arms or cheeks.

Low Vitamin B-12. Omeprazole can cause you to absorb less vitamin B-12 than usual, which can cause low vitamin B-12 levels. You have a higher risk of this if you take omeprazole for a long time (3 years or longer). Stop using omeprazole and call your health care provider if you have any of the following symptoms.

  • Sore tongue
  • Weakness 
  • Tingling or numbness in your hands or feet

Low Magnesium. Omeprazole can cause low magnesium levels, also known as hypomagnesemia, which can be serious. Decreased magnesium levels can cause seizures or heart rhythm problems. You may be at higher risk if you take the omeprazole for a long time or take other medicines that also cause low magnesium. Stop using omeprazole and call your health care provider if you have any of the following symptoms.

  • Changes in your heart rate or rhythm, such as fast or skipping heartbeat
  • Dizziness 
  • Muscle spasms
  • Seizures 

Bone Loss and Fractures. Omeprazole may cause bone loss and increase your risk for fractures. The risk is higher in older adults and people taking omeprazole for a long time or taking a high dose.

Warnings & Precautions

Who should not use omeprazole?

Allergies to Ingredients. People who are allergic to any of the following should not use omeprazole.

  • Omeprazole
  • Prilosec
  • Prilosec OTC
  • Any other medicine known as a proton pump inhibitor
  • Any of the ingredients in the specific product dispensed

Your pharmacist can tell you all of the ingredients in the specific omeprazole products they stock.

Drug Interactions. Omeprazole should not be taken while you are using certain other medicines. Before taking omeprazole, tell your health care provider about any prescription or over-the-counter (OTC) medicines, vitamins/minerals, herbal products, and other supplements you are using. See the Interactions section for more details.

What should I know about omeprazole before using it?

If omeprazole was prescribed to you by a health care provider, use it as prescribed. If you are using over-the-counter omeprazole, follow the instructions that come with the product.

Do not share omeprazole that was prescribed for you by a health care provider with other people, even if they have the same condition as you. It may harm them.

Keep omeprazole out of the reach of children.

Do not chew, cut, or crush omeprazole.

Take omeprazole before a meal.

Antacids may be taken with omeprazole if needed.

If you are having trouble swallowing the omeprazole capsule, you may open them and sprinkle the contents on 1 tablespoon of applesauce. Swallow the applesauce right away. Don’t mix it with any other food.

Omeprazole should not be used for immediate relief of heartburn. It may take 1 to 4 days for the medicine to fully work.

What should I tell my health care provider before using omeprazole?

Tell your health care provider about all of your health conditions and any prescription or over-the-counter (OTC) medicines, vitamins/minerals, herbal products, and other supplements you are using. This will help them know if omeprazole is right for you.

Current and Past Health Conditions. Tell your health care provider if you have any of the following.

  • Low blood potassium level (hypokalemia)
  • Low blood magnesium level (hypomagnesemia)
  • Low blood calcium level (hypocalcemia)
  • Liver problems

Other Medicines and Supplements. Omeprazole may interact with other medicines and supplements. Before using omeprazole, tell your health care provider about any prescription or over-the-counter (OTC) medicines, vitamins/minerals, herbal products, and other supplements you are using. See the Interactions section for more details.

Pregnancy. It is not known if or how omeprazole could affect pregnancy or harm a fetus. Tell your health care provider if you are or plan to become pregnant. Your health care provider will let you know if you should take omeprazole while you are pregnant or trying to get pregnant. 

Breastfeeding. Omeprazole can pass into breast milk. Tell your health care provider if you are breastfeeding or plan to breastfeed. Your health care provider will let you know if you should take omeprazole while breastfeeding.

Interactions

Does omeprazole interact with foods or drinks?

Take omeprazole before meals.

It is unknown if drinking alcohol will affect omeprazole.

Does omeprazole interact with other medicines (drug interactions)?

Always tell your health care provider about any prescription or over-the-counter (OTC) medicines, vitamins/minerals, herbal products, and other supplements you are using.

In particular, make sure that you discuss if you are using any of the following before using omeprazole.

  • Clopidogrel (Plavix) or cilostazol (Pletal), which are antiplatelet medicines used to prevent blood clots
  • Citalopram, which is a medicine used to treat depression
  • Methotrexate (Trexall and others)
  • Digoxin (Lanoxin), which is a medicine used to treat irregular heartbeat and some types of heart failure
  • Warfarin, which is used as a blood thinner
  • Certain antiretroviral medicines, such as rilpivirine (Edurant), nelfinavir (Viracept), or saquinavir (Invirase), which are used for HIV or AIDS
  • St. John’s Wort, which is a supplement that may be used for depression
  • Rifampin, which is a medicine commonly used to treat an infection called tuberculosis

Some other medicines may alter the blood levels of omeprazole, and vice versa. Omeprazole may also affect the absorption of some other medicines. Tell your health care provider about all medicines that you take or have recently taken. Always tell your health care provider about any prescription or over-the-counter (OTC) medicines, vitamins/minerals, herbal products, and other supplements you are using.

This may not be a complete list of medicines that can interact with omeprazole. Always check with your health care provider.

Does interact with other drugs you are taking?

Enter your medication into the WebMD interaction checker

Overdose/Missed Dose

What should I do if I accidentally use too much omeprazole?

If you or someone else has used too much omeprazole, get medical help right away, call 911, or contact a Poison Control center at 800-222-1222.

What should I do if I miss a dose of omeprazole?

If you miss a dose, take it as soon as you remember. If it is almost time for your next dose, skip the missed dose and only take the next dose. Do not take double or extra doses.