Vitamin-B12 Status of Patients on Long-term Metformin Therapy

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Abstract
Vitamin-B12 malabsorption has been found in 21 (30%) of 71 diabetic patients taking long-term metformin therapy in addition to dietary management. The patients with evidence of B12 malabsorption had significantly lower haemoglobin levels (and significantly higher serum folic acid levels) than those with normal B12 absorption. Steatorrhoea was found in only one patient. Stopping metformin therapy resulted in reversion of B12 absorption to normal in most patients examined. Four patients with B12 malabsorption were found to have pathologically low serum B12 levels. The causes and implications of these findings are discussed and it is concluded that all patients on long-term metformin therapy should have annual serum B12 estimations.