Metformin use suppresses serum levels of vitamin B12
Serum levels of vitamin B12 fall in patients taking high doses of metformin, a new study has found.
Researchers from the University of Liverpool examined serum B12 levels in blood samples from 50 patients with type 2 diabetes prescribed metformin for at least three months.
Their findings, newly published in the British Journal of Clinical Pharmacology, show a dose-dependent relationship between total daily metformin dose and serum B12 concentration. Patients on a daily dose of metformin of 3,000mg had an average serum concentration of vitamin B12 of around 200ng/l, only around half that of patients on a daily dose of 500mg.
Lead researcher Dr Simon Constable, lecturer in clinical pharmacology and therapeutics at the University of Liverpool, said: 'The model indicates that as the total daily dose of metformin increases, serum B12 concentrations will be reduced.
'There is a dose-dependent relationship between total daily metformin dose and serum B12 concentration.'