When Do I Need To Sign Up For Medicare? 
As explained above , when you turn 65 you are automatically enrolled in Medicare Part A . As long as you are a citizen , or a legal resident and have worked 40 quarters in the United States , this benefit will be free . If you have worked less than the 40 quarters , you may be able to buy the Part A benefit . In addition , if you are under 65 and disabled you may also be eligible for Medicare coverage . Part B of Medicare is optional unlike Part A . If you are enrolled in Part A and have insurance through your employer , you may not have to enroll in Part B , which costs $ 104.90 per month . However , if you want to benefit from full Medicare coverage , you will need Part B as well as Part A . In addition , if you would like to enroll in supplementary insurance in addition to Medicare -LRB- Medigap , Medicare Advantage orPart DRx coverage -RRB- , you must be enrolled in both Part A and Part B. 