Nutrition-related vitamin B12 deficiency in patients in Pakistan with type 2 diabetes mellitus not taking metformin.

Objective: To estimate the frequency of undiagnosed vitamin B12 deficiency among patients with type 2 diabetes mellitus who had not taken metformin during at least the prior 5 years and to ascertain whether vitamin B12 deficiency among the patients with type 2 diabetes was due to nutritional deficiency or malabsorption.

Methods: Serum vitamin B12 levels were measured in 44 subjects with diabetes and a mean age of 51 years (range, 40 to 70), 21 (48%) of whom had low levels (<200 pg/mL). Of those 21 patients, 10 agreed to enroll in an intervention phase consisting of oral supplementation with mecobalamin, 1,500 microg daily for 3 months. Those patients in whom vitamin B12 levels failed to normalize after oral supplementation alone would be presumed to have vitamin B12 deficiency attributable to malabsorption.

Results: Almost half of the subjects with type 2 diabetes not taking metformin had biochemically proven vitamin B12 deficiency. All 10 subjects who enrolled in the intervention phase had normalization of their vitamin B12 levels after 3 months of oral supplementation with mecobalamin.

Conclusion: We conclude that vitamin B12 deficiency is common among patients with type 2 diabetes and was related to nutrition in our study group. In addition to intensive glycemic control, vitamin B12 supplementation should be considered for treatment of diabetic neuropathy. In almost 50% of patients with low vitamin B12 levels, the deficiency was corrected with oral supplementation only. This, indeed, is an important finding, inasmuch as oral vitamin B12 supplementation is easy, convenient, and readily accepted by patients. This finding highlights the need for aggressive and early diagnosis and treatment to avoid complications of vitamin B12 deficiency.