A medical system for performing a therapeutic function on a patient comprises an implantable medical device having a switching function to switch from a normal operating mode to an MRI compatible operating mode in the presence of an MRI device, and an external device for programming at least one setting of the implantable medical device. The external device is configured, based on a programming event relating to said at least one setting, to generate a notification prompting a user to confirm a continuing MRI compatibility of said MRI compatible operating mode after the programming event and/or to amend said at least one setting for achieving MRI compatibility.