The 65th birthday is that milestone birth year where Medicare automatically kicks in, except for those who choose to decline Medicare coverage and self insure. I did not consider that a viable option, so it was important for me to make my decision on the provider for my Medicare Supplement, commonly called "Medi-Gap", so that it would be in place at the same time Medicare goes into effect (this is the coverage that pays what Medicare denies). Same for Medicare Part D (prescription drug plan) and there are some strategies for that based on what medications you take monthly. That key date is the 1st of the month before your 65th birthday, and there is a specific window of time, defined by law, where one can select the company and plan that they want and pre-existing conditions are not considered. If one waits and allows that window to close, then one must "apply" for the supplemental and Part D coverage, and the company considers all information, including pre-existing conditions, in their decision to accept or deny coverage and I believe in establishing their premium. Buy during the "window" before your birthday month and it's simple. Wait and it might be more painful.