Background: Metformin reduces intestinal absorption of Vitamin B12 in up to 30% of patients and lowers serum Vitamin B12 concentrations in 5-10%. In 2017, the American Diabetes Association (ADA) updated its guidelines to recommend patients taking metformin undergo regular monitoring of Vitamin B12 levels. To better understand acceptance and application of these guidelines, we undertook an assessment of such monitoring within a single hospital center serving the low-income population in Atlanta, GA to assist in guiding optimal monitoring and patient management.

Methods: Data was collected from a single hospital center using electronic medical records (EMR) and the SlicerDicer tool to identify all outpatients for whom metformin was prescribed either as a single agent or in combination therapy during January 1 - December 31, 2021 and then measure Vitamin B12 prescribing among primary care patients and patients followed by endocrinology and further analyze which patients had neuropathy.

Results: During the period studied, of the total 2,336,914 patients documented in the EMR, 30,803 (0.01%) were outpatients prescribed metformin either as a single agent or in combination therapy. Of these, 816 patients (2.6%) had Vitamin B12 levels ordered and measured. The prevalence of Vitamin B12 levels ordered and measured was 7.5% (674 of 8,975) among patients seen in primary care clinics and 2.3% among those followed in endocrinology (25 of 1,081) (chi-square p<0.0001) . 621 (6.9%) of the metformin-treated primary care patients had neuropathy, and of those 63 had Vitamin B12 levels. 134 (12.4%) of the endocrinology patients had neuropathy, and of those 5 had Vitamin B12 levels. (chi-square p<0.0001)

Conclusion: Among two outpatient cohorts who were prescribed metformin, there was suboptimal adherence to the ADA’s recommendation for regular monitoring of Vitamin B12 levels. Approaches for increasing and optimizing ordering and monitoring Vitamin B12 levels will be developed. Increased awareness of the relationship between metformin and Vitamin B12 deficiency and standardized approaches to monitoring are needed.


R. D. Ghiya: None. M. Fayfman: None.

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