Severe and long-lasting diarrhea not recognized as adverse effect of low dose metformin

Publication of the United Kingdom Prospective Diabetes Study (UKPDS) in 2006 [1], resulted in metformin being considered the first choice for new-onset diabetes type-2 in many international guidelines significantly increasing its use. [2,3]. The number of metformin users in the Netherlands increased with 43% between 2005 and 2009 from 27.5 to 39.4 per 1000 patients [4]. Although relatively safe, metformin has a high prevalence of gastrointestinal adverse effects. In 2009 three patients were admitted to our geriatric department for metformin-induced long-lasting disabling diarrhea. We describe one of these cases.