Can I Take These?

Can You Take Metformin and Vitamin B12 Together?

Long-term metformin use can lower vitamin B12 levels -- its FDA label recommends periodic monitoring, not avoidance.

MonitorEvidence: High

What the interaction means

Metformin's FDA prescribing information states: "In controlled clinical trials of Metformin Hydrochloride Tablets USP of 29 weeks duration, a decrease to subnormal levels of previously normal serum vitamin B12 levels, without clinical manifestations, was observed in approximately 7% of patients." The label attributes this to possible interference with B12 absorption from the B12-intrinsic factor complex, and describes the effect as "very rarely associated with anemia and appears to be rapidly reversible with discontinuation of Metformin Hydrochloride Tablets USP or vitamin B12 supplementation."

Why it may happen

The FDA label attributes this to possible interference with vitamin B12 absorption from the B12-intrinsic factor complex.

Practical context

The label recommends measuring hematologic parameters on an annual basis in patients taking metformin, and for patients at higher risk (inadequate vitamin B12 or calcium intake or absorption), "routine serum vitamin B12 measurements at two- to three-year intervals" may be useful. This is framed as a periodic monitoring item, not something requiring the medication to be avoided or spaced apart from B12.

What the sources say

Metformin Hydrochloride Tablets, USP — FDA Prescribing Information — Granules Pharmaceuticals Inc. (via DailyMed, U.S. National Library of Medicine)

Last reviewed 2026-08-22

Medical information disclaimer: this information is general and educational. It does not diagnose conditions, prescribe treatment, or determine whether a combination is safe for you personally. Follow your prescription label and ask a pharmacist or clinician before starting, stopping, or combining products. Full disclaimer.

Related interactions