The Effect of Metformin on Vitamin B12 Deficiency and Stroke.

BACKGROUND: Type 2 diabetes mellitus (T2DM) is a known risk factor for cardiovascular disease and stroke. Metformin is an old, relatively safe, first line therapy for T2DM; however, it has been associated with stroke.

OBJECTIVES: To study the effects of metformin use and vitamin B12 deficiency on stroke rate among patients with T2DM.

METHODS: We conducted a prospective study of patients admitted with ischemic stroke within 12 months (starting March 2020). We studied the clinical impact of metformin on vitamin B12 deficiency and stroke evolution. Student's t-test and ANOVA were used to compare the groups of patients and to determine whether there was any direct or indirect effect of metformin use on vitamin B12 deficiency and stroke.

RESULTS: In total, 80 patients were admitted with ischemic stroke. Clinical status and biochemical data were collected and compared with healthy volunteers. There were 39 diabetic patients, 16 took metformin for at least 1 year. Among those who took metformin for at least 1 year, 9 had vitamin B12 level < 240 pg/ml (56.2%); 23 diabetic patients did not get metformin and only 4 had vitamin B12 level < 240 pg/ml (17.4%) (P = 0.014).

CONCLUSIONS: T2DM is a significant risk factor to the development of ischemic stroke. We found an association between metformin use and vitamin B12 deficiency and an association between vitamin B12 deficiency and stroke risk in patients with T2DM. Diabetic patients who are taking metformin should monitor their vitamin B12 level.