Incidence of Type II Diabetes Mellitus (T2DM) is increasing; majority of which is managed in primary care. NICE recommends starting Metformin as a first-line therapy. Studies have linked Metformin use with Vitamin B12 deficiency and suggest that regular monitoring of levels is warranted. The pathogenesis is not fully understood. Literature suggests that the risk of developing B12 deficiency is greatly influenced by high doses and long duration of therapy. An audit was conducted at Hucknall Road Medical Centre in Nottingham, to determine whether GPs are checking serum B12 level in patients on Metformin. The first phase of the audit concluded that 64% of patients have not had their Vitamin B12 tested. The first phase revealed that 6.4% of the patients were already deficient and on replacement injections while on Metformin. The second phase of the audit determined whether patients would comply if invited to have their Vitamin B12 tested. Second phase showed 72.2% compliance and the rate of Vitamin B12 deficiency was 6% in those tested. Overall, phase 1 and phase 2 combined showed that 9.6% diabetics on Metformin were Vitamin B12 deficient. The British Society of Haematology recommends that B12 levels are checked when there is clinical suspicion of deficiency in patients. However, peripheral neuropathy caused by Diabetes and B12 deficiency is irreversible therefore it may be too late if checked when symptoms develop. The prevalence of Vitamin B12 deficiency among Metformin-treated patients ranges between 5.8% and 52%. A study concluded that patients on long-term Metformin are twice as likely to develop peripheral neuropathy compared to those on other anti-diabetic regimes. There are no guidelines to clarify the surveillance of Vitamin B12 while on Metformin. The work has led to change in practice at the medical centre, whereby patients will have their B12 checked on the annual diabetic check.