Prevalence of vitamin B12 deficiency among metformin-treated type 2 diabetic patients in a tertiary institution, South-South Nigeria.

BACKGROUND: The risk of chronic metformin pharmacotherapy to cause vitamin B12 deficiency and its associated medical complications has been of immense concern among diabetic patients. Some studies have postulated that vitamin B12 deficiency is highly prevalent among chronic metformin-treated adult diabetic patients. AIM: This study aimed to determine the prevalence of vitamin B12 deficiency among metformin-treated and metformin-naïve type 2 diabetes mellitus patients. MATERIALS AND METHODS: This was a case-control, prospective, analytical, observational study of 200 adult participants (100 per group) attending the Endocrinology, Medical Out-patients Clinic of Irrua Specialist Teaching Hospital, Irrua, Edo State, Nigeria. The participants' serum vitamin B12 levels were determined using an immunoassay technique. Data were presented using tables and charts. Chi-square test was used to compare non-continuous proportional variables. RESULTS: The prevalence of vitamin B12 deficiency was 41% and 20% among metformin-treated and metformin-naïve type 2 diabetes mellitus groups, respectively (p = 0.001). Borderline vitamin B12 status was present among 59% of metformin-treated group and 80% of metformin-naïve group (p = 0.001). Neither metformin-treated nor metformin-naïve groups had normal serum vitamin B12 levels. CONCLUSION: The prevalence of vitamin B12 deficiency was significantly high in diabetics, especially the metformin-treated patients. We advocate for vitamin B12 supplementation among this group of patients in order to prevent the occurrence of vitamin B12 deficiency complications such as macro-ovalocytic anemia, impaired immunity with hypersegmented neutrophils, peripheral neuropathy and subacute degeneration of the spinal cord.