how to tell medicare co-pay for diabetes drugs

i have a patient with medicare. i don't know his exact prescription plan and i'm not sure if he would know either or how to find out. i need to know what his co-pay costs would be for trulicity and insulin. i need to be able to factor affordability before prescribing. the best tool i can think of medicare compare plans website. does anyone know of a better resource? thank you.
Source: Student Doctor Network - Category: Universities & Medical Training Authors: Tags: General Residency Issues Source Type: forums