NSTK · 01.2026Independent supplement reference
NutriStack
Edition 1.0Updated August 1, 2026

Supplement × Prescription·Evidence index

Omeprazole and Vitamin B12: what the published research says

PubMed indexes 8 records that name Omeprazole and Vitamin B12 together, either in the title or in an interaction, co-administration, or pharmacokinetic context. Each one is listed below with its study design and, where the abstract states one, the authors’ own conclusion, quoted and linked. This page reports that literature. It does not tell you whether to combine them.

Read this first

An evidence index, not guidance.

Every statement below is attributed to a named, dated, linked source.

This page lists published research relevant to Omeprazole and Vitamin B12. It deliberately does not state whether the combination is safe, whether it interacts, in which direction, at what dose, or how far apart to take them.

The research

8 studies naming Omeprazole and Vitamin B12.

Strongest relevance first: papers naming both substances in the title, then human trials and systematic reviews.

Effect of hypochlorhydria due to omeprazole treatment or atrophic gastritis on protein-bound vitamin B12 absorption.

Journal of the American College of Nutrition · 1994 · PMID 7706591

Clinical TrialRandomized Controlled TrialResearch Support, U.S. Gov't, Non-P.H.S.

“Omeprazole causes protein-bound vitamin B12 malabsorption, and ingestion of an acidic drink improves protein-bound vitamin B12 absorption.”

Saltzman et al. · Authors' conclusion

Names both Omeprazole and Vitamin B12 in its title.

Omeprazole and vitamin B12 deficiency.

The Annals of pharmacotherapy · 1999 · PMID 10369631

ReviewHuman subjects

“All healthcare workers should be made aware of the potential clinical complications of omeprazole-associated vitamin B12 deficiency since it may go unrecognized and is easily corrected. This is particularly relevant for elderly patients with poor dietary intake of vitamin B12, impaired vitamin B12 stores, and certain gastrointestinal disorders.”

Bradford et al. · From the abstract

Names both Omeprazole and Vitamin B12 in its title.

Effect of CYP2C19 polymorphism on serum levels of vitamin B12 in patients on long-term omeprazole treatment.

Alimentary pharmacology & therapeutics · 1999 · PMID 10215728

Human subjects179 participants

“CYP2C19 polymorphism significantly affected serum vitamin B12 levels in patients on long-term therapy with omeprazole. In the future, genotyping of CYP2C19 may be useful for patients in need of long-term treatment with omeprazole or other proton pump inhibitors.”

Sagar et al. · Authors' conclusion

Names both Omeprazole and Vitamin B12 in its title.

Omeprazole and vitamin B12.

Annals of internal medicine · 1994 · PMID 8198354

CommentLetterHuman subjects

Names both Omeprazole and Vitamin B12 in its title.

Limitations

What this evidence cannot tell you.

Search-based evidence indexes have real limits, and it is worth being explicit about them:

NutriStack

Track what you actually take.

NutriStack is a free iPhone app for organising a supplement routine: what you take, when, and what the published record says about it. Its exploratory interaction checker covers Omeprazole, Vitamin B12, and several hundred other substances.

The checker is a research and organisation tool, not a clinical decision aid, and its per-pair assessments are excluded from search until they pass claim-level review.

NutriStack is an informational and organizational tool, not a medical service, and not a substitute for professional advice. Always consult a qualified healthcare professional before starting, stopping, or changing any supplement or medication.