ONE-YEAR INCIDENCE AND DETERMINANTS OF VITAMIN B12 DEFICIENCY IN NEWLY DIAGNOSED TYPE 2 DIABETES MELLITUS PATIENTS INITIATED ON METFORMIN: A PROSPECTIVE COHORT STUDY

Abstract

Metformin is the first-line therapy for type 2 diabetes mellitus and is widely prescribed at diagnosis. Long-term use of metformin has been linked to vitamin B12 deficiency, but prospective Indian data on early incidence after initiation of therapy are limited.

Objectives: To determine the one-year incidence of vitamin B12 deficiency among newly diagnosed type 2 diabetes mellitus patients with normal baseline vitamin B12 levels who were initiated on metformin.

Methods: This prospective observational cohort study was conducted at a tertiary care teaching hospital in India. A total of 112 newly diagnosed type 2 diabetes mellitus patients with normal baseline serum vitamin B12 levels were enrolled at the time of initiation of metformin therapy and followed for one year. Participants were reviewed at three-month intervals, and serum vitamin B12 levels were measured at each follow-up visit. Baseline demographic, clinical, haematological, and biochemical parameters were recorded.

Results: Over one year, 21 participants (18.75%) developed incident vitamin B12 deficiency. Participants who developed deficiency were significantly older and more likely to follow a vegetarian diet, receive higher daily doses of metformin, have lower baseline haemoglobin levels, and use proton pump inhibitors. On multivariable analysis, increasing age, vegetarian diet, metformin dose ≥1500 mg/day, lower baseline haemoglobin, and proton pump inhibitor use were independently associated with vitamin B12 deficiency.

Conclusions: Vitamin B12 deficiency can develop within the first year of metformin therapy in newly diagnosed type 2 diabetes mellitus patients. Early and risk-based monitoring of vitamin B12 levels should be considered, particularly in patients with identifiable risk factors.