Trends in Vitamin B12 Level Testing in Patients on Metformin From 2000 to 2020

Metformin is one of the primary pharmacologic agents for managing type 2 diabetes mellitus (T2DM). However, it has been associated with interference in vitamin B12 absorption and deficiency. Vitamin B12 deficiency and T2DM can present diagnostic challenges for polyneuropathy. Diagnosis is essential for guiding treatment, yet the use of vitamin B12 level testing in this population may have dwindled over time amid changing practice guidelines. This study examines trends over time in the use of vitamin B12 level testing among patients on metformin.

This retrospective trend analysis used data from TriNetX, a real-world, longitudinal clinical database. Patients treated with metformin from 2000 to 2020 were identified using Rx Concept Unique Identifier codes. The number of patients who underwent vitamin B12 level testing at any time after 1 month from metformin initiation was tabulated. Patients were grouped by the year of B12 level testing. Trends in B12 level testing were assessed using the Jonckheere-Terpstra statistical test (P<.05).

Out of 4,203,020 patients prescribed metformin, 1,055,995 (25.1%) underwent B12 level testing. The highest proportion of patients tested was in 2000 to 2002 (39.6%), while the lowest proportion was in 2018 to 2020 (20.1%). B12 testing utilization declined significantly by 19.5% from 2000-2002 to 2018-2020 (P=.001).

In this study, we found that the use of vitamin B12 level testing in patients on metformin has significantly declined over the years, potentially impacting early detection of B12 deficiency. Future studies with more granular data from real-life practice are recommended to understand the precise reasons and impact of this trend.