Does Omeprazole Affect Vitamin B12 Levels? An In-depth Analysis

October 13, 2025 •

3 min read

Chronic use of proton pump inhibitors (PPIs), such as omeprazole, for more than two to three years has been consistently linked to an increased risk of vitamin B12 deficiency. This well-established risk is a direct consequence of the medication's primary function: suppressing the production of stomach acid.

Quick Summary

Long-term omeprazole use can interfere with the body's absorption of dietary vitamin B12 because it reduces stomach acid, a prerequisite for the vitamin's release from food. Increased risk is associated with extended therapy and higher doses, especially in older adults and those with specific dietary habits.

Key Points

Omeprazole suppresses stomach acid: The medication reduces stomach acid, which is necessary to release vitamin B12 from dietary protein for absorption.
Risk increases with time and dose: Long-term use (over 2-3 years) and higher doses of omeprazole significantly raise the risk of developing a B12 deficiency.
Higher risk for specific populations: Elderly individuals, vegetarians, vegans, and those on other medications like metformin are at greater risk.
Supplementation is a common solution: Supplemental (crystalline) vitamin B12 is absorbed without stomach acid, making oral supplements an effective way to prevent or treat deficiency.
Regular monitoring is recommended: For patients on long-term therapy, periodic monitoring of B12 levels is prudent to catch potential deficiencies early.

The Intricate Link Between Omeprazole and Vitamin B12

Omeprazole, a proton pump inhibitor, effectively treats conditions like GERD, peptic ulcers, and Zollinger-Ellison syndrome by reducing gastric acid production. While beneficial for these conditions, this acid suppression can impact the absorption of nutrients, including vitamin B12, which requires an acidic environment for proper absorption. For dietary vitamin B12, which is bound to protein in food, to be absorbed, it must first be released in the stomach, requiring adequate stomach acid and pepsin. Omeprazole hinders this initial step, reducing the amount of B12 that can be freed from food proteins. While not completely blocking absorption, particularly of free B12 found in supplements, it can significantly decrease the efficiency of absorbing food-bound B12 with long-term use. Once freed, B12 binds to intrinsic factor made in the stomach, and the complex travels to the small intestine for absorption. By limiting the release of B12 from food, omeprazole ultimately reduces the formation of this essential B12-intrinsic factor complex. More information on the mechanism can be found on {Link: DrOracle website https://www.droracle.ai/articles/103798/can-omeprazole-causes-b12-deficiency-}.

Factors Increasing the Risk of Deficiency

Factors influencing the risk of developing a vitamin B12 deficiency while taking omeprazole include the duration and dosage of therapy. Older adults, those with diets low in animal products, individuals taking certain concurrent medications like metformin, and those with underlying digestive conditions may also face increased risk. The FDA suggests a risk after more than three years, and studies indicate increased risk with use exceeding two years. Further details on risk factors are available on {Link: DrOracle website https://www.droracle.ai/articles/154073/what-are-some-negative-side-effects-of-long-term-omeprazole-and-define-long-term}.

Recognizing the Signs and Symptoms

Vitamin B12 deficiency can present with various symptoms, including fatigue, weakness, anemia, neurological issues like numbness and tingling, balance problems, memory issues, and cognitive decline, as well as mood changes and a swollen tongue. {Link: DrOracle website https://www.droracle.ai/articles/103798/can-omeprazole-causes-b12-deficiency-} provides more information on potential symptoms.

Diagnosing and Managing Deficiency

Monitoring B12 levels through blood tests or a methylmalonic acid test is important for patients on long-term omeprazole, especially if symptoms occur. Omeprazole does not interfere with the absorption of crystalline B12 found in most supplements, making oral supplementation an effective management strategy. B12 injections may be necessary in more severe cases.

Comparison of Omeprazole Effects on B12 Absorption


Aspect	Long-term Omeprazole Use	Vitamin B12 Supplements (Crystalline B12)
Effect on Dietary B12 Absorption	Significantly impairs by suppressing stomach acid, preventing release from food proteins.	Has no impact on the absorption of dietary B12.
Effect on Supplemental B12 Absorption	Does not affect the absorption of crystalline (unbound) B12 found in supplements.	Excellent absorption, as it does not require stomach acid for release.
Mechanism	Impairs the acid-dependent release of B12 from food.	Bypasses the stomach acid-dependent step entirely.
Risk of Deficiency	Increased risk with higher doses and longer duration, particularly in vulnerable groups.	No risk of deficiency, and is used to correct it.

Taking Action: A Proactive Approach

Healthcare providers and patients should monitor B12 status during long-term omeprazole therapy, especially in high-risk individuals. This may involve testing or supplementation. Discussing the benefits and risks of continued PPI therapy with a doctor is essential, and alternative therapies or dose adjustments may be considered.

Conclusion: Balancing the Benefits and Risks

Omeprazole can impact vitamin B12 levels by hindering the absorption of dietary B12 over extended periods due to its effect on stomach acid. The risk, while generally uncommon for severe deficiency, is higher for those on high doses, long-term therapy, or with other risk factors. This risk is manageable through monitoring and supplementation with crystalline vitamin B12. Patients should consult their healthcare provider to balance the benefits of omeprazole with potential nutritional risks. {Link: DrOracle website https://www.droracle.ai/articles/103798/can-omeprazole-causes-b12-deficiency-}

Frequently Asked Questions

Omeprazole works by suppressing stomach acid. Stomach acid and the enzyme pepsin are required to cleave vitamin B12 from the proteins in food. By reducing the acidity, omeprazole inhibits this process, leading to impaired absorption of dietary B12.

No, the risk is not immediate. The body has large stores of vitamin B12, so a deficiency typically takes many years of continuous omeprazole use to develop. The risk is primarily associated with long-term therapy, generally considered to be over two to three years.

Symptoms can include fatigue, weakness, anemia, numbness, tingling in the hands and feet, memory problems, balance issues, and a swollen tongue (glossitis).

Yes. Supplemental vitamin B12 (cyanocobalamin) is in a free, or crystalline, form that does not require stomach acid for absorption. Therefore, oral B12 supplements are an effective way to address or prevent deficiency in patients taking omeprazole.

High-risk groups include the elderly, people on high doses or long-term therapy (over two years), vegans and vegetarians, and individuals with other conditions like Crohn's disease or those taking metformin.

All proton pump inhibitors work by suppressing stomach acid, so all have the potential to affect dietary B12 absorption with long-term use. Observational studies have noted similar associations across the class of drugs.

No, you should not stop any prescribed medication without first consulting your doctor. A healthcare professional can assess your risk, test your B12 levels, and recommend appropriate management strategies, which might include supplementation or adjusting your medication.