Introduction: The worldwide prevalence of DM has risen dramatically in past two decades, an estimated 30 million cases in 1985 to 285 million in 2010 and according to International Diabetes Federation it will be 438 million by the year 2030. Aims and objectives: The basic aim of the study is to analyze the frequency of vitamin B12 deficiency in type 2 diabetic patients taking metformin therapy in Pakistan. Material and methods: This cross-sectional study was conducted in Allama Iqbal Memorial Teaching Hospital, Sialkot during September 2018 till March 2019. The data was collected from 100 patients. The patients of both genders, aged between 30-80 years, diagnosed cases of Diabetes Mellitus type 2 and on metformin therapy for more than one year was included in this study. Blood was drawn for the analysis of serum. Serum B12 level was checked by Roche B12 kit. The rationale to check HbA1c is to look for the control of sugars. Results: The data was collected from 100 patients of both genders. Mean age (years) in the study was 54.08+13.74 with ranges from 20 to 80 years. Distribution of gender of patient was also calculated in terms of frequency and percentage of male and female patients. Mean duration of plasma sugar level was 16.02+3.55 in the study. Descriptive statistics of serum vitamin B12 level was calculated in terms of mean and standard deviation. Mean serum vitamin B12 level was 102.67+28.10 in the study. Conclusion: It is concluded that frequency of vitamin B12 deficiency is substantial in type 2 diabetic patients taking metformin therapy.