In a 24-week study of initial combination therapy with sitagliptin and metformin administered twice daily (sitagliptin/ metformin 50 mg/ 500 mg or 50 mg/ 1,000 mg), the overall incidence of adverse reactions considered as drug-related in patients treated with the combination of sitagliptin and metformin compared to patients treated with placebo was 14.0% and 9.7%, respectively.