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Research Preview — Unreviewed AI Research

Metformin

biguanide antihyperglycemic

Also sold as Glucophage.

Recognized as Metformin. The supported evidence in this preview concerns Vitamin B12 (cobalamin).

Researched 9/3/2026

Evidence summary

Qualifying findings
1
Interactions and timing
0
Searched, nothing found
0
Verified cited sources
1 of 1
Human review
Not yet reviewed
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Overview

Research Preview — Unreviewed AI Research

AI-assisted Research Preview - not yet human-reviewed and not part of Published Knowledge.

This is automated research that has not yet been reviewed by a person. It is not MyDeficiencies published knowledge, it is not medical advice, and it may be incomplete or wrong. It has been added to our editorial review queue.

biguanide antihyperglycemic. Recognized as Metformin. The supported evidence in this preview concerns Vitamin B12 (cobalamin).

Researched 9/3/2026 · Adversarial review ran: 4 confirmed, 1 scope corrections, 1 rejected.

1 of 1 cited sources were confirmed to exist as described. That check confirms the source is real, not that it supports the claim.

What the research found

Evidence for this exact medication is kept strictly apart from evidence that comes only from its drug class.

Direct evidence for this medication

Measured decrease in nutrient status

Vitamin B12 (cobalamin)

exact entity

Direct evidence for this medication

A large, long-term study (the Diabetes Prevention Program Outcomes Study, following adults with prediabetes for up to 13 years) found that people taking metformin were more likely to have low or borderline-low B12 levels than those on placebo, with the likelihood rising the longer metformin was used.

1 cited source and detail

Human studies that measured this nutrient in people taking this exact medication.

Relationship:
medication -> vitamin status (Direction A)
Outcome measured:
Measured decrease in nutrient status
Study population:
human studies
Agreement:
1 supporting, 0 contradicting

What was measured: serum vitamin B12 concentration; incidence of low/borderline-low B12

Proposed mechanism: The proposed explanation, stated in the medication's own labeling, is that metformin may interfere with how the body absorbs vitamin B12 using a protein called intrinsic factor. A mechanism explains how an effect could occur. It is not itself a measured clinical outcome.

1 of 1 cited sources were checked and found to support this specific claim. A source existing is not the same as a source supporting the claim.

Why it is here: Concordant official-label statement and a large, long-duration randomized controlled trial analysis.

Evidence limitations

What this cannot tell you

  • The long-term study population was adults with prediabetes rather than the general population of people using metformin for diabetes, though the underlying absorption mechanism would be expected to apply more broadly.
  • Vitamin D status remains an open, unresolved gap (contradictory secondhand citations only, no independently verified primary source). The folate-reducing primary study (Wulffele 2003) remains unretrieved from its primary source.

AI-assisted Research Preview - not yet human-reviewed and not part of Published Knowledge. Educational information only. Not medical advice, diagnosis or treatment. Talk to your prescriber or pharmacist before changing any medication or supplement.

Sources

Only sources attached to information shown above are listed here.

  • Long-term Metformin Use and Vitamin B12 Deficiency in the Diabetes Prevention Program Outcomes Study

    2016 · RCT with long-term open-label extension (metformin n=1073, placebo n=1082; up to 13 years) · human study

    PMID 26900641· identifier confirmed to exist (PMID)

    https://pubmed.ncbi.nlm.nih.gov/26900641/
  • Existence of a source and support for a claim are checked separately. A confirmed identifier means the record is real, not that it supports the statement it is cited for.

Questions for your clinician

These are conversation prompts, not findings about you.

  • Could Metformin affect any nutrients over time in my situation?
  • Are there symptoms or risk factors that would make further evaluation appropriate?
  • Could diet, other medications, or health conditions affect this relationship?
  • Would laboratory testing be clinically appropriate for me?
  • Are there medication or supplement interactions I should understand?

Review status

Human review

Published Knowledge is human-reviewed. Research Previews are clearly labeled and have not yet completed human review.

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Derived from acceptance run artifacts/candidate-workbooks/MyDeficiencies_Claude_Cardiovascular_Candidate_Intelligence_Batch-001_FINAL-CORRECTED_2026-09-02.xlsx (373fbbf11d03).