Vitamin B12 status and peripheral neuropathy in patients with type 2 diabetes mellitus

To assess the status of vitamin B12 in patients with type 2 diabetes, and to explore any association between its deficiency and diabetic peripheral neuropathy.

This cross-sectional observational study was conducted from August, 2017, to April, 2018, at the Specialized Centre for Endocrinology and Diabetes in Baghdad, Iraq. Type 2 diabetics using metformin were subjected to clinical examination for retinopathy using fundoscopy, and peripheral neuropathy using the Michigan Neuropathy Screening Instrument. Additionally, patients were asked to fill a questionnaire and their medical records were reviewed. Blood samples were obtained for the measurement of biomarkers. Vitamin B12 deficiency was recorded at ≤187 pg/ml. Data was analysed using SPSS 25.

Of the 66 patients, 39(59%) were males and 27(41%) were females. The overall mean age was 53.3}9.2 years and the mean duration of diabetes was 104}71.8 months. The mean dose of metformin was 1135}496 mg and the duration of metformin use was 72}62 months. Overall, 19(29%) patients suffered from vitamin B12 deficiency. However, no significant difference was found between normal and deficit groups regarding the parameters that may affect vitamin B12 level. Also, no significant correlations were found between vitamin B12 concentration and the dose (p=0.16) or the duration of metformin use (p=0.09).

High prevalence of vitamin B12 deficiency was observed in metformin-treated patients with type 2 diabetes. However, the deficiency had no correlation with the rate of peripheral neuropathy.