"...Federal employees have numerous questions as they plan for their retirement from federal service. One of the most often-asked questions is whether a federal retiree, a CSRS or a FERS annuitant, should enroll in Medicare when he or she becomes first eligible...
This column will attempt to answer this question and will also answer other frequently asked questions, namely:
When should federal retirees enroll in Medicare and in which parts of Medicare?
Is there a late enrollment penalty for Medicare and when does the penalty apply?
Which is “primary” coverage – FEHB or Medicare?..."
Read more at My Federal Retirement