Based on NIH | Can omeprazole cause nausea, how common is this side effect, and what should I do if it happens?

Yes omeprazole can cause nausea. It is listed among the most common side effects reported in both adults and children, alongside headache, stomach pain, diarrhea, gas, and sometimes vomiting. ^[1] Nausea was reported in approximately 4% of omeprazole‑treated participants in clinical trials, which places it in the “common” range (≥2%). ^{[2] [3]}

How common nausea is

• In pooled clinical trial data summarized in the official prescribing information, nausea occurred in about 4% of people taking omeprazole. Other common events included headache (~7%), abdominal pain (~5%), diarrhea (~4%), vomiting (~3%), and flatulence (~3%). ^{[2] [3]}
• Consumer medication guides for omeprazole also list nausea among the most frequent side effects seen in everyday use. This aligns with clinical trial findings that nausea is a relatively common but usually mild reaction. ^{[1] [4]}

Why nausea may happen

• Omeprazole reduces stomach acid (it’s a proton pump inhibitor), which can change how the stomach digests food and how the gut moves. These changes can, in some people, lead to temporary stomach upset, including nausea. ^[1]
• Importantly, the labeling indicates most common side effects tend to be mild and self‑limited. They typically do not require stopping therapy if symptoms are tolerable. ^{[1] [4]}

What to do if you feel nauseated

• Adjust timing and administration:
  • Take omeprazole before eating (usually 30–60 minutes before breakfast), and swallow capsules or tablets whole as directed. For those who cannot swallow capsules, certain products allow sprinkling the capsule contents on applesauce follow product‑specific instructions. ^[5]
• Supportive self‑care:
  • Eat small, bland meals; avoid rich, spicy, or fatty foods that can worsen stomach discomfort. Lifestyle tips commonly recommended for acid symptoms (e.g., avoiding late meals, elevating the head of the bed) may also ease overall stomach upset. ^[6]
• When to keep going vs. call your clinician:
  • If nausea is mild and short‑lived, it may be reasonable to continue while monitoring, as common side effects are often temporary. If nausea persists, becomes bothersome, or is accompanied by vomiting, abdominal pain, or weight loss, you should contact a healthcare professional to reassess treatment. ^{[7] [1]}
  • Seek urgent care if you develop severe symptoms such as widespread rash with blisters, difficulty breathing, or signs of a serious reaction. While rare, serious adverse events require immediate attention per patient information guides. ^[8]

Could it be something else?

• Nausea can have many causes, such as other medications, infections, reflux flares, or dietary triggers. If symptoms started soon after beginning omeprazole and improve when the medicine is paused on a clinician’s advice, it may suggest a drug side effect. ^[1]
• Long‑term use of proton pump inhibitors has been linked to low magnesium in some people, usually after at least three months (often after a year). Low magnesium can cause nonspecific symptoms; if you are on prolonged therapy and feel unwell, your clinician may check magnesium levels. ^[7]

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Quick reference: How common is nausea with omeprazole?

Side effect (adults in trials)	Approximate rate
Headache	~7% [2] [3]
Abdominal pain	~5% [2] [3]
Nausea	~4% [2] [3]
Diarrhea	~4% [2] [3]
Vomiting	~3% [2] [3]
Gas (flatulence)	~3% [2] [3]

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Bottom line

• Yes, omeprazole can cause nausea and it occurs in about 4% of users in clinical studies, making it a common but typically mild side effect. ^{[2] [1]}
• Try taking the medication as directed before meals, keep meals small and bland, and monitor symptoms; contact a clinician if nausea is persistent, troublesome, or accompanied by other warning signs such as vomiting, stomach pain, or weight loss. ^{[5] [6] [7]}