Vitamin B12 deficiency in patients with type 2 diabetes on metformin therapy

Abstract

Background: Vitamin B12 deficiency can cause peripheral neuropathy. Metformin use is associated with vitamin B12 deficiency. Objective: To define the prevalence of vitamin B12 deficiency in patients with type 2 diabetes mellitus (T2DM) and its possible relation to metformin therapy. Patients and Methods: A crosssectional study of T2DM patients on chronic metformin therapy was conducted at Benghazi Diabetic Center during 2011. Demographic data, type, and duration of treatment reported adherence, and vitamin B treatment were all documented. History and examination for evidence of peripheral neuropathy were recorded. Serum vitamin B12 levels were measured (reference value 159-1000 pg/ml). Results: 500 patients were included of whom 175 were males (35%). Mean (SD) age was 58.6 ± 9.9 years and duration of diabetes 13.6 ± 8.4 years. Of these 358 (71.8%) were on insulin and metformin' 93 (18.6%) on sulphonylureas and metformin, 26 (5.2%) were on insulin and sulphonylurea and metformin triple monotherapy. Mean serum B12 level for all patients was 439 ± 212 pg/ml with males having significantly higher levels than females (512 ± 226 vs. 399± 193; p=0.001). Vitamin B12 levels were <159 pg/ml in 2%, <200 p g/ml in 7.4%, and <300 pg/ml in 30.8% of the patients. There was no significant difference in the B12 levels among patients who were adherent to metformin therapy and those who were not (432 ± 206 vs. 448 ± 219 pg/ml; p=0.4). Serum B12 levels were not different in the patient with history and/or examination suggestive of neuropathy and patients who have any (443 ± 216 vs. 423 ± 204; p=0.5. Conclusions: The prevalence of vitamin B12 deficiency in diabetic patients attending Benghazi diabetic center was dependent on the cut off points used. This is comparable with previous studies. No clear relationship was evident with metformin therapy nor with neuropathy.