What are the most common side effects of omeprazole?
The most common side effects of omeprazole are listed below. Tell your healthcare 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 healthcare 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 doctor right away.
Antibiotic-associated Diarrhea. An overgrowth of germs called Clostridioides difficile, or “C. diff,” can happen in your gut during treatment with omeprazole. Call your healthcare 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 develop a rash, stop omeprazole and call your healthcare provider right away. Get emergency help right away if you have any of the following symptoms of SJS or TEN.
- Painful red or purple skin that looks burned and peels off
- Flat red rash or blisters on your skin, mouth, nose, and genitals
- Red, painful, watery eyes
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 allergic reaction.
- Skin rash or pale red bumps on the skin called hives
- Fever or general ill feeling
- Swollen lymph nodes
- Shortness of breath
- Swelling in your feet, ankles, or legs
- Dark colored urine
- 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.
Vitamin B-12 deficiency. 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 healthcare provider if you have any of the following symptoms.
- Sore tongue
- Weakness
- Tingling or numbness in your hands or feet
Hypomagnesemia. Omeprazole can cause low magnesium levels, also known as hypomagnesemia, which can be serious. Decreased magnesium levels can cause seizures or heart rhythm problems. Some people have a higher risk of this, including people who take the omeprazole for a long time or those that take other medicines that can cause low magnesium. Stop using omeprazole and call your healthcare 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.
Severe Allergic Reactions. Omeprazole may cause allergic reactions, which can be serious. Stop using omeprazole and get help right away if you have any of the following symptoms of a serious allergic reaction.
- Breathing problems or wheezing
- Racing heart
- Fever or general ill feeling
- Swollen lymph nodes
- Swelling of the face, lips, mouth, tongue, or throat
- Trouble swallowing or throat tightness
- Itching, skin rash, or pale red bumps on the skin called hives
- Nausea or vomiting
- Dizziness, feeling lightheaded, or fainting
- Stomach cramps
- Joint pain
