Endocrine Abstracts

Background: Metformin has been shown from observational studies to cause vitamin B12 deficiency and its complications. However there is no such study in Kano, Northwestern Nigeria which has a large population of patients with type 2 diabetes mellitus on metformin.

Objective: To determine the prevalence of Vitamin B12 deficiency among patients with type 2 diabetes mellitus on metformin therapy compared with metformin-naïve patients with diabetes and healthy individuals

Methods: It was a hospital-based, case-control prospective, analytical, observational study. Three hundred participants were recruited, 100 metformin-treated patients with diabetes, 100 metformin-naïve patients with diabetes and 100 non-diabetic patients. Questionnaire was used to evaluate the clinical and laboratory features of the participants. Vitamin B12 was assayed using Beckman access immunoassay system. Peripheral neuropathy was tested using biothesiometer. Data was analysed using SPSS.

Results: Most of the participants were females above 40 years of age. Vitamin B12 deficiency occurred among 24% of metformin-exposed patients with diabetes mellitus, 8% of metformin-naïve patients with diabetes and 5% of participants without diabetes mellitus. Metformin exposure, dose and duration of the drug therapy were found to be significantly associated with the development of vitamin B12 deficiency (P<0.05). However, among metformin-naïve participants, the duration of diabetes mellitus was significantly associated with vitamin B12 deficiency. The dose of metformin was an independent predictor for the development of vitamin B12 deficiency among metformin exposed participants (OR 3.5, 95% CI 1.330-9.368). There was a statistically significant relationship between the vitamin B12 deficiency and the development of peripheral neuropathy and macrocytic anaemia among the three groups of participants.

Conclusion: High doses of metformin causes vitamin B12 deficiency among patients with type 2 diabetes mellitus. Hence there is need for regular screening of these individuals when they are on long term therapy to prevent and alleviate the complications of vitamin B12 deficiency.