Israel Medical Association Journal

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.

Background: Concerns about metformin-associated lactic acidosis (MALA) prohibit the use of metformin in a large subset of diabetic patients, mostly in patients with chronic kidney disease. Increasing evidence suggests that the current safety regulations may be overly restrictive.

Objectives: To examine the association between chronic metformin treatment and lactate level in acute illness on the first day of admission to an internal medicine ward.

Methods: We compared diabetic and non-diabetic hospitalized patients treated or not treated with metformin in different sets of kidney function.

Results: A total of 140 patients participated in the study, 54 diabetic patients on chronic metformin treatment, 33 diabetic patients without metformin and 53 patients with no diabetes. Most participants were admitted for conditions that prohibit metformin use, such as heart failure, hypoxia and sepsis. Average lactate level was significantly higher in the diabetes + metformin group compared to the diabetes non-metformin group. Metformin treatment was not associated with higher than normal lactate level (hyperlactatemia) or low pH. No patient was hospitalized for lactic acidosis as the main diagnosis.

Conclusions: Chronic metformin treatment mildly increases lactate level, but does not induce hyperlactatemia or lactic acidosis in acute illness on the first day of admission to an internal medicine ward. These data support the expansion of metformin use.