Objective: As oral hypoglycemic agent Metformin therapy is the gold standard treatment for type 2 diabetic patients. Long term use of metformin has been associated with vitamin B12 deficiency. We aimed to study the level of vitamin B12 in type 2 diabetic patients on metformin, and to determine other factors affecting the level of vitamin B12. Methodology: In tertiary care institute 300 patients with type 2 diabetes that were interviewed from January to December 2017 & investigated for vitamin B12 levels deficiency. Result: Most of the patients, 56.4% had a normal vitamin B12 level. Dyslipidemia and hypertension were significantly more (p=0.007 and 0.012 respectively) in patients with normal vitamin B12 level. Percentage of normal B12 level patients was higher (p=0.001) even in more than 20 years of metformin use; 37.2% of more than 20 years Metformin users had vitamin B12 level within 301–450 pg/mL and 23.2% had more than 450 pg/mL. Conclusion: We recommend routine screening for basal vitamin B12 level for all patients with type 2 diabetes mellitus (T2DM) at the initiation of metformin therapy with subsequent annual follow up of the level.