Anticoagulants are common medications that carry the potential for serious harm if administered incorrectly. This retrospective review of 8,576 patients with atrial fibrillation who received direct oral anticoagulants identified inappropriate dosing in nearly 15% of cases, with most patients receiving an inappropriately low dose. Over one year of follow-up, the authors did not identify any significant difference in the incidence of stroke, embolism, bleeding, or ischemic attacks between patients who were inappropriately, versus appropriately, dosed.