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Family Medicine

Training Level

Resident PGY 2


Henry Ford Hospital


Background: Metformin and its ability to cause vitamin B12 deficiency has been thoroughly studied and documented. Despite this, there is no formal screening recommendation. Our study investigates: whether there is a benefit to a formal screening guideline and, if so, when is it appropriate to screen for vitamin B12 deficiency in patients on Metformin. We additionally investigated quantifying if vitamin B12 testing is completed.Methods:We conducted a retrospective cohort study on a population of HAP patients who were ever tested for Vitamin B12 deficiency. Our exposed group was comprised of patients who had filled at least two prescriptions of Metformin between 1/1/2010 to 10/1/2016. Our unexposed group was not exposed to Metformin. Patients were followed through 12/31/2018 for vitamin B12 testing and deficiency. Results:Amongst our exposed population of 13489 patients, 44.86% of patients were tested for Vitamin B12 deficiency. Average time to test was 990 days, the average time to test positive was 1831 days. Factors associated with testing for B12 deficiency were male gender (41.5%), older age (62.79% in patients over 80 years old), Caucasian race (48.98%), and malabsorption syndromes (71.7%) including bariatric surgery, celiac disease, small bowel disease, and PPI use. Amongst tested patients in the exposed population, it was found that 3.34% had vitamin B12 deficiency. The only factor associated with deficiency in a multivariable analysis was older age. African American ethnicity approached significance as a protective factor. Discussion: While we found testing to be suboptimal, vitamin B12 deficiency incidence was lower than expected. On chart review it was found that reasons for testing for B12 level included anemia, cognitive decline, and neuropathy. This implies that patients were having symptoms of deficiency leading to testing. Our study found that 3.34% of patients exposed to Metformin had vitamin B12 deficiency. Of patients not exposed to Metformin, 2.14% were found to have deficiency.

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Should Patients on Metformin Be Screened for Vit B12 Deficiency, and if so When?