The prevalence of low vitamin B12 status in people with type 2 diabetes receiving metformin therapy in New Zealand--a clinical audit

Abstract

Aim: Metformin, the most common hypoglycaemic agent used in type 2 diabetes, is associated with reduced serum vitamin B12 concentrations. This cross sectional observational study determines the prevalence of low vitamin B12 status in people with type 2 diabetes on metformin therapy in both primary and secondary care in New Zealand.

Method: All eligible patients seen in a secondary-care clinic over a 15-month timeframe were screened for low serum vitamin B12 concentrations. Additionally, patients from four primary health care providers were identified using metformin prescription data and offered the chance to participate in the audit.

Results: Prevalence of serum Vitamin B12 level <220 pmol/L was 18.7%. Positive correlations were observed between B 12 concentration, age and dosage and duration of metformin treatment. Maori and Pacific Islanders had higher mean serum B12 concentrations than Europeans but no difference in prevalence of low serum B12 concentrations.

Conclusion: Low serum B12 concentration is a common occurrence in people with type 2 Diabetes treated with Metformin. Age is an important factor which explains some of this association. Systematic screening in those receiving metformin is advisable, particularly for patients older than 50 years.