484 adult patients with type 2 diabetes mellitus will be randomized to one of two arms. 242 will be assigned to the intervention (My Diabetes Care) embedded within an existing patient web portal, My Health at Vanderbilt at Vanderbilt University Medical Center or Patient Gateway at Brigham and Women's Hospital. 242 will be assigned to a usual care comparison arm with access currently available version of My Health at Vanderbilt or Patient Gateway without the My Diabetes Care (MDC) application. Potentially eligible patients will be invited to be screened for enrollment in the study. Interested patients will be able to complete an electronic consent form and enroll online via Research Electronic Data Capture (REDCap). Outcomes data will be collected from patients at four time points: baseline (T0), three-month follow-up (T1), three-month follow-up (T2), six-month follow-up (T3), and twelve-month follow-up (T4). At each time point, study participants will complete questionnaires electronically via email using REDCap, participants' hemoglobin A1C level will be assess via home A1C test kits, and participants' diabetes health data will be abstracted from their electronic health record. Participants will be randomized to the intervention or control arm after their baseline data is collected.