OBJECTIVES: Improving medication adherence is a key population health management strategy. We describe a 6-month cross-section of users of the Care4Today® Mobile Health Manager (C4T) mobile phone application, which enables self-directed medication management. We focus on metformin users given the high prevalence of diabetes, and compare to all other C4T users (not using metformin). METHODS: De-identified, self-reported data from C4T from 6/15/15-12/15/15 were analyzed. Patients were grouped by total number of medications managed (1, 2-3, 4-5, 6+). The percentage of medications taken was calculated by dividing the number of doses marked as taken by the total number of required doses. Active users were those using C4T to mark ≥30% of tracked medications as taken. RESULTS: A total of 309 metformin and 3,017 non-metformin users were identified. Separate demographic surveys of C4T users indicated two-thirds are ages 45+, and 55% are male. During the study period, 309 metformin users tracked 367,639 total medication doses for all medications (average 6.6 doses/patient/day), marking 79% as taken. For comparison, 3,017 C4T users not using metformin tracked 1,978,123 total doses, marking 77% taken (average 3.6 doses/patient/day). Active metformin users (n=272), marked 86% of overall doses as taken (82%, 83%, 82%, and 86%, for users tracking 1, 2-3, 4-5, and 6+ medications, respectively). Active non-metformin users (n=2,504), marked 85% of overall doses as taken (81%, 84%, 84%, and 86%, for users tracking 1, 2-3, 4-5, and 6+ medications, respectively).  CONCLUSIONS: The percentage of medications taken (proxy for medication adherence) by C4T users was in the 85% range. Users managing 6+ medications marked more medications taken than those managing fewer medications, suggesting the utility of a mobile health application for staying on a medication schedule. Future research may identify traits of self-selected, actively engaged mobile health users, and compare self-reported data to pharmacy refill claims data.