Evaluation of Vitamin B 12 Monitoring in a Veteran Population on Long-Term,High-Dose Metformin Therapy

Abstract

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French

BACKGROUND:

Metformin can result in vitamin B₁₂ deficiency, potentially leading to complications such as neuropathy. Annual monitoring of vitamin B₁₂ has been suggested; however, it is unknown whether current practice reflects this recommendation.

OBJECTIVE:

To identify vitamin B₁₂ monitoring patterns in patients on long-term, high-dose metformin. Secondary objective was to determine the frequency of new vitamin B₁₂ deficiency, anemia, and neuropathy documented after initiation of high-dose metformin.

METHODS:

Electronic medical records of veterans treated at the Veterans Affairs Maryland Healthcare System with high-dose metformin (≥2000 mg/day) as of November 1, 2010, were reviewed. Data regarding metformin treatment, vitamin B₁₂ measurements, and documentation of vitamin B₁₂ deficiency, cyanocobalamin supplementation, anemia, and neuropathy were collected. Subjects treated with metformin for less than 1 year or those with documented peripheral neuropathy, megaloblastic anemia, vitamin B₁₂ deficiency, or a condition associated with vitamin B₁₂ malabsorption prior to metformin initiation were excluded.

RESULTS:

Subjects (N = 235) had a mean metformin dose of 2050 mg/day and mean duration of treatment of 5.2 years. Sixty percent did not have vitamin B₁₂ measured. Of subjects receiving metformin for 10 years or more, nearly half (46%) never had vitamin B₁₂ measured. New documentation of vitamin B₁₂ deficiency or cyanocobalamin supplementation was found in 5.5% of the population, and anemia was found in 12%. Of the 14% with new neuropathy, 42% did not have vitamin B₁₂ measured.

CONCLUSIONS:

Vitamin B₁₂ was not routinely monitored in patients on high-dose metformin, even in those at highest risk (≥10 years of therapy), or in those with potential manifestations of vitamin B₁₂ deficiency (neuropathy). Cases of vitamin B₁₂ deficiency and resulting anemia or neuropathy may be undiagnosed and untreated because of lack of monitoring. Prospective studies examining the effect of increased vitamin B₁₂ monitoring on identification and treatment of vitamin B₁₂ deficiency in patients on metformin are warranted.

Keywords

diabetes metformin monitoring neuropathy

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