Does omeprazole cause adverse effects?

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Last updated: April 15, 2025View editorial policy

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From the Guidelines

Omeprazole can cause various side effects, including common effects like headache, nausea, and diarrhea, as well as more serious but less common effects such as vitamin B12 deficiency, magnesium deficiency, and increased risk of bone fractures, as reported in a 2021 study 1. The use of omeprazole, a proton pump inhibitor (PPI), is effective for treating conditions like GERD, peptic ulcers, and other acid-related disorders, but its mechanism of reducing stomach acid production by blocking the proton pump in gastric parietal cells also explains some of its potential side effects. Some key points to consider when evaluating the potential side effects of omeprazole include:

  • Common side effects: headache, nausea, diarrhea, stomach pain, and flatulence
  • More serious but less common effects: vitamin B12 deficiency, magnesium deficiency, increased risk of bone fractures, and kidney problems with long-term use
  • Rare but severe effects: severe allergic reactions
  • Long-term use associations: slightly increased risks of community-acquired pneumonia, Clostridium difficile infections, and certain nutritional deficiencies It is essential to consult a healthcare provider if concerning symptoms are experienced while taking omeprazole, rather than stopping the medication abruptly, as the benefits of the medication for treating specific conditions can outweigh the risks of side effects for many patients, as suggested by studies such as the one published in 2006 1.

From the FDA Drug Label

Omeprazole delayed-release capsules can cause serious side effects, including: • A type of kidney problem (tubulointerstitial nephritis). • Diarrhea. • Bone fractures. • Certain types of lupus erythematosus. Omeprazole delayed-release capsules can have other serious side effects. What are the possible side effects of omeprazole delayed-release capsules Omeprazole delayed-release capsules can cause serious side effects, including: • Vitamin B-12 deficiency. • Low magnesium levels in your body. • Stomach growths (fundic gland polyps) The most common side effects with omeprazole delayed-release capsules in adults and children include: • headache • stomach pain • nausea • diarrhea • vomiting • gas

Omeprazole can cause several side effects, including:

  • Serious side effects: kidney problems, diarrhea, bone fractures, and certain types of lupus erythematosus
  • Common side effects: headache, stomach pain, nausea, diarrhea, vomiting, and gas
  • Other side effects: vitamin B-12 deficiency, low magnesium levels, and stomach growths (fundic gland polyps) 2, 2

From the Research

Omeprazole Side Effects

  • Omeprazole, a proton pump inhibitor (PPI), has been associated with several potential side effects, including:
    • Bone fractures: Studies have shown that long-term use of PPIs, including omeprazole, may increase the risk of osteoporosis and fractures 3, 4, 5, 6
    • Nutritional deficiencies: PPIs may lead to deficiencies in vitamin B12 and magnesium, although the clinical relevance of this is unclear 3
    • Gastrointestinal infections: PPIs may increase the risk of enteric infections, including Clostridium difficile-associated diarrhea (CDAD) 3, 5, 7
    • Acute interstitial nephritis: PPIs have been associated with an increased risk of acute interstitial nephritis, although this is rare 3, 7
    • Rebound acid hypersecretion: Stopping PPIs after long-term use may lead to rebound acid hypersecretion, although this can be managed with lifestyle modifications and alternative therapies 7

Patient Considerations

  • Patients taking omeprazole should be monitored for potential side effects, particularly those at higher risk, such as older adults and those with a history of fractures or gastrointestinal infections 3, 5, 7
  • Alternative therapies, such as histamine-2-receptor antagonists, may be considered for patients who require long-term acid suppression therapy 7
  • Lifestyle modifications, including weight loss, upright head of bed elevation, and avoiding high-fat meals close to bedtime, may help reduce the risk of rebound hypersecretion and other side effects 7

References

Guideline

Guideline Directed Topic Overview

Dr.Oracle Medical Advisory Board & Editors, 2025

Research

Proton pump inhibitors: potential adverse effects.

Current opinion in gastroenterology, 2012

Research

Proton pump inhibitors and osteoporosis.

Current opinion in rheumatology, 2016

Research

Proton pump inhibitors: Understanding the associated risks and benefits of long-term use.

American journal of health-system pharmacy : AJHP : official journal of the American Society of Health-System Pharmacists, 2023

Research

Proton Pump Inhibitor Use in Older Adults: Long-Term Risks and Steps for Deprescribing.

The Consultant pharmacist : the journal of the American Society of Consultant Pharmacists, 2018

Professional Medical Disclaimer

This information is intended for healthcare professionals. Any medical decision-making should rely on clinical judgment and independently verified information. The content provided herein does not replace professional discretion and should be considered supplementary to established clinical guidelines. Healthcare providers should verify all information against primary literature and current practice standards before application in patient care. Dr.Oracle assumes no liability for clinical decisions based on this content.

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