Although patients taking metformin had significantly lower fasting and postprandial plasma glucose and hemoglobin A1C concentrations, they also had a higher prevalence of Gastrointestinal (GI) side effects. The most commonly reported symptoms was diarrhea (53,2 % compared to 11,7% on placebo). In a study employing self-administered questionnaires to ascertain GI symptoms in patients with type 2 diabetes approximately 20% of those taking immediate-release metformin reported diarrhea as the most common symptoms. Although less than 5% of patients discontinue metformin treatment for this reason, such adverse events can be troublesome, may limit the dosage of metformin and may impair compliance with therapy. Glucophage XR may lead to improved tolerability, by smoothing the peaks and troughs in metformin plasma concentrations and delaying the achievement of peak plasma concentration, compared with an immediate-release formulation. Initial placebo-controlled clinical trials with Glucophage XR indicate that 9,6% patients reported diarrhea (compare to 1,5% on placebo).