When Can I Join A Medicare Advantage Plan? 
You can enroll in a Medicare Advantage plan when you are first eligible for Medicare Part A and Part B. For most people that will be when they turn age 65 . If you are approved for Social Security disability -LRB- SSDI -RRB- you should qualify for Medicare after 2 years on SSDI . If you are covered on an employer group health insurance plan beyond age 65 you can enroll in an Advantage plan when your group health plan terminates . 