The aim of this study was to examine the prescribing patterns and use of antiobesity medications in a large cohort of patients using data from electronic health records.Pharmacy- and patient-level electronic health record data were obtained on 2,248,407 adults eligible for weight-loss medications from eight geographically dispersed health care organizations.A total of 29,964 patients (1.3% of total cohort) filled at least one weight-loss medication prescription. This cohort was 82.3% female, with median age 44.9 years and median BMI 37.2 kg/m2 . Phentermine accounted for 76.6% of all prescriptions, with 51.7% of prescriptions being filled for ≥ 120 days and 33.8% filled for ≥ 360 days. There was an increase of 32.9% in medication days for all medications in 2015 compared with 2009. Higher prescription rates were observed in women, black patients, and patients in higher BMI classes. Of 3,919 providers who wrote at least one filled prescription, 23.8% (n = 863) were "frequent prescribers" who wrote 89.6% of all filled prescriptions.Weight-loss medications are rarely prescribed to eligible patients. Phentermine accounted for > 75% of all medication days, with a majority of patients filling it for more than 4 months. Less than one-quarter of prescribing providers accounted for approximately 90% of all prescriptions.