OBJECTIVE To understand the burden of medication use for patients with newly diagnosed diabetes both before and after diabetes diagnosis and to identify subpopulations of patients with newly diagnosed diabetes who face a relatively high drug burden. DESIGN Retrospective cohort study. SETTING 11 integrated health systems in the United States. PARTICIPANTS 196,654 insured adults 20 years of age or older newly diagnosed with type 1 or type 2 diabetes from January 2005 through December 2009. MAIN OUTCOME MEASURES Number of unique therapeutic classes of drugs dispensed in the 12 months before and 12 months after diagnosis of diabetes in five categories: overall, antihypertensive agents, antihyperlipidemic agents, mental health agents, and antihyperglycemic agents (in the postdiagnosis period only). RESULTS The mean number of drug classes used by newly diagnosed patients with diabetes is high before diagnosis (5.0) and increases significantly afterward (6.6). Of this increase, 81% is due to antihyperglycemic initiation and increased use of medications to control hypertension and lipid levels. Multivariate analyses showed that overall drug burden after diabetes diagnosis was higher in women, older, white, and obese patients, as well as among those with higher glycosylated hemoglobin concentrations and comorbidity levels (significant for all comparisons). The overall number of drug classes used by newly diagnosed patients with diabetes after diagnosis decreased slightly but significantly between 2005 and 2009. CONCLUSION Patients newly diagnosed with diabetes face a substantially increased burden of medications used to control diabetes and other comorbidities. This study shows an increased focus on cardiovascular disease risk factor control after diagnosis of diabetes. However, total drug burden may be slightly decreasing over time.