Prevalence of Vitamin B12 deficiency in patients with type 2 diabetes mellitus on Metformin therapy at a single centre in Johannesburg, South Africa

Abstract

Abstract Introduction: Metformin is a first-line oral hypoglycaemic agent for treating patients with type 2 diabetes mellitus (T2DM). Studies suggest that metformin use is associated with B12 deficiency. There is a paucity of data regarding this association in South Africa. The current study aimed to determine the prevalence of B12 deficiency in a South African cohort of T2DM patients on metformin therapy. Methods: The study was a retrospective clinical audit of patients recruited from a medical outpatient setting. A consecutive sampling technique was employed; T2DM patients who were 40 years or older and on metformin for a minimum of 6 months were recruited. B12 deficiency was defined as severe (<150 pmol/L), moderate (150–169 pmol/L) or mild (170–200 pmol/L). Results: One hundred and one (n = 101) patients were enrolled, most of whom were females (65%). The prevalence of B12 deficiency was 14.9%, with most patients in the mild category. The majority of B12 deficient patients were female (67%), elderly (70.2 ±10.7 years) and of Coloured race (67%). The median duration of metformin use in B12 deficient and non-deficient patients was 10.9 (6–13) and 7 (3–12) years respectively (p =0.179). The median metformin dosage was 1700 mg. Older age (Adjusted odd ratio (AOR) 6.67 (1.16–38.3), p = 0.033) and Coloured race (AOR 7.8(1.78–34.2) p = 0.006) were associated with vitamin B12 deficiency. Conclusion: In our setting, vitamin B12 deficiency is prevalent amongst T2DM patients on metformin therapy. Older age and the novel finding of Coloured race were associated with B12 deficiency. We recommend screening for B12 deficiency amongst T2DM patients on metformin therapy.