Can Omeprazole Cause Low Vitamin B12? Understanding the Risks

October 13, 2025 •

3 min read

Studies indicate that long-term use of acid-suppressing medications, including omeprazole, is linked to a higher risk of low vitamin B12 levels. This association stems from the crucial role stomach acid plays in vitamin B12 absorption.

Quick Summary

Omeprazole's reduction of stomach acid can impair vitamin B12 absorption, increasing deficiency risk with long-term use, higher doses, and in older adults. Monitoring and supplementation are key management strategies.

Key Points

Omeprazole lowers stomach acid: This reduces the release of B12 from food proteins, impairing absorption.
Affects dietary B12: The primary effect is on B12 from food, while supplements are less affected.
Risk factors include duration and dose: Long-term use (over 2-3 years) and higher doses increase the risk of deficiency.
Vulnerable populations: Older adults and those with poor diet face a higher risk.
Monitoring and supplementation are key: At-risk patients should be monitored, and deficiency is treated with supplements.
Potential neurological effects: Severe deficiency can lead to serious neurological issues.

How Omeprazole Impacts Vitamin B12 Absorption

Omeprazole is a proton pump inhibitor (PPI) that reduces stomach acid production. While effective for conditions like GERD, this action can interfere with the body's ability to absorb vitamin B12.

The Normal Process of B12 Absorption

Proper vitamin B12 absorption begins in the stomach, where acid releases the vitamin from food proteins. The freed B12 then binds to proteins and intrinsic factor for absorption in the small intestine.

Omeprazole's Interference

By decreasing stomach acid, omeprazole hinders the initial step of separating B12 from food, thereby reducing the amount available for absorption. This mainly affects B12 from food; the absorption of unbound B12 in supplements is less impacted.

Risk Factors and Monitoring

The risk of developing B12 deficiency while taking omeprazole depends on several factors. Longer durations of treatment and higher doses are associated with increased risk. Elderly individuals may also be more vulnerable. Because the body stores B12, deficiency symptoms may not appear right away. Monitoring is important for patients on long-term therapy, especially those with higher risk factors. While routine screening isn't universally recommended, it might be considered for at-risk patients on prolonged treatment. Potential symptoms of deficiency include fatigue, neurological issues, cognitive difficulties, mood changes, and anemia.

Management Strategies and Alternatives

Addressing B12 deficiency in patients using omeprazole often involves supplementation. Oral B12 supplements are usually effective because their absorption doesn't rely on stomach acid. In more severe cases, B12 injections might be necessary. Dietary adjustments can also play a supportive role. Discussing potential dose adjustments or alternative medications with a healthcare provider is also an option.

Managing B12 Deficiency in PPI Users

Supplementation: Oral supplements are a common approach; injections are used for severe cases or when oral absorption is insufficient.
Dietary Adjustments: Incorporating B12-rich foods into the diet can be helpful.
Treatment Review: Consulting a doctor to evaluate the omeprazole dosage or explore alternative therapies is recommended.

Comparison of B12 Supplementation Options


Feature	Oral B12 Supplementation	Intramuscular (IM) B12 Injections
Mechanism of Absorption	Absorbed without need for significant stomach acid or intrinsic factor.	Bypasses the digestive system, absorbed directly into the bloodstream.
Suitability for PPI Users	Well-suited, as absorption is less affected by reduced gastric acid.	Suitable for all patients, especially those with severe deficiency or poor oral absorption.
Recommended for	Mild to moderate deficiency; long-term prevention.	Severe deficiency, neurological symptoms, or confirmed malabsorption.
Administration	Daily or as prescribed; available in various forms.	Administered by a healthcare professional; typically less frequent.
Cost and Convenience	Generally more affordable and convenient for regular use.	Can be more costly and requires healthcare visits.

Conclusion: Balancing Treatment and Nutrition

Omeprazole provides important therapeutic benefits, especially for short-term use. However, prolonged high-dose treatment is associated with a higher likelihood of vitamin B12 deficiency. Managing this risk involves talking with a doctor, monitoring individuals at higher risk, and using appropriate supplementation if needed. Being aware of the potential for deficiency supports safer medication use and helps protect nutritional health. The official FDA drug labeling for omeprazole offers more information {Link: FDA https://www.accessdata.fda.gov/drugsatfda_docs/label/2012/019810s096lbl.pdf}.

The Role of Bacterial Overgrowth

Besides reduced stomach acid, small intestinal bacterial overgrowth (SIBO) might contribute to B12 malabsorption during long-term PPI use. Stomach acid helps control bacteria in the small intestine. Lower acid levels can lead to bacterial growth, which might consume B12, reducing its availability for absorption. The full impact of SIBO on B12 levels is still being researched {Link: droracle.ai https://www.droracle.ai/articles/103798/can-omeprazole-causes-b12-deficiency-}.

Frequently Asked Questions

Clinically significant B12 deficiency from omeprazole is uncommon with short-term use. It typically requires prolonged therapy, often years, to deplete the body's B12 stores.

Early symptoms can be non-specific, such as fatigue and weakness. More pronounced deficiency may cause neurological symptoms like numbness, tingling, and memory issues.

Yes, taking B12 supplements, especially oral forms, can help prevent or treat deficiency while on omeprazole. Supplemental B12 doesn't require stomach acid for absorption in the same way dietary B12 does.

Since all PPIs work similarly by reducing stomach acid, they all carry a potential risk of B12 deficiency. However, specific risk may vary based on dose and duration.

Discontinuing omeprazole, under medical supervision, may help normalize stomach acid levels. However, existing deficiency typically requires supplementation to correct, especially if it was severe.

For patients on long-term therapy, particularly those at higher risk, doctors may periodically check serum B12 levels or other related markers like methylmalonic acid.

Discussing alternatives with your doctor is important. Options might include other acid-reducing medications (like H2 blockers, which have a lower risk) or lifestyle and dietary changes.