Adolescents commonly experience barriers to adherence that entail forgetfulness, distraction, poor planning, and scheduling problems. A once daily oral regimen may be superior to the current regimens that require twice daily dosing. It is currently unclear if Envarsus XR® would improve outcomes in adolescent organ transplant recipients. Each patient will receive tacrolimus (twice daily immediate release oral formulation) which they are using as part of their standard of care immunosuppressive regimen for a portion of the study and Envarsus XR® (a once daily extended-release oral tacrolimus formulation) for a portion of the study in a cross-over design. Besides the advantage to adherence behaviors, a sustained-release tacrolimus preparation may decrease burdensome side effects and increase quality of life. Following enrollment, each patient will be maintained in the study for 9 months.