Is the Use of Metformin Associated with Vitamin B12 Deficiency in Hospitalized Patients?
Madill J, Hartman B, Donnelly-VanderLoo, Smeall K, Siswanto O, Watson T and O’Connor C
Journal Title:Journal of Clinical Nutrition and Food Science
Objective: The primary objective was to determine the prevalence of vitamin B12 deficiency and subclinical deficiency among metformin users in various clinical settings across Southwestern Ontario. The secondary objective was to determine the relationship between metformin use and B12 deficiency. Methods: A retrospective chart review was conducted on patients admitted to emergency, neurology, critical care and trauma, and spinal cord and stroke rehabilitation units in 3 hospitals across Southwestern Ontario between January 2010 and December 2012. A total of 710 electronic charts were studied through random sampling. Results: Overall prevalence of impaired B12 status (< 220 pmol/L) among the entire patient population with B12 data were 18.6% (n=391) and 24% among metformin users (n=78, P < 0.0001). The majority of metformin users were not likely to take a B12 supplement (P=0.0065). The 2 patients on metformin who were both classified as being B12 deficient, however, only 53% of those with subclinical deficiency were taking a B12 supplement. B12 supplement administration did differ by hospital site in those with subclinical B12 deficiency status (148-220 pmol/L, P=0.0334). Conclusion: This study reports a higher prevalence of B12 deficiency among metformin users than the general patient population. Metformin users with overt B12 deficiency were taking B12 supplements but only half of those with subclinical deficiency were using a B12 supplement. Recommendations for B12 supplement use among those with subclinical status vary by institution. Measuring methylmalonic acid [MMA] to determine functional B12 status may ensure those with subclinical deficiencies receive treatment, and this should become the standard medical approach.