You can enroll into a Medicare drug plan when you first become eligible for Medicare.  This period is known as your Initial Enrollment Period. If you get Part B for the first time between January 1st and March 31st, you may join a drug plan during that time-period as well.  That time-period is known as the General Enrollment Period. Individuals eligible for Extra Help can enroll at any time.

 

Once you enroll into a Medicare drug plan, generally, you must remain enrolled for the entire calendar year. Certain situations allow you to switch, drop, or join a Medicare drug plan during other times such as: 1) if you move out of the plan’s service area 2) you lose your current creditable prescription drug coverage 3) live in a nursing home or other like-type institution 4) you are a Medicaid recipient 5) you are eligible for Extra Help

 
My Drugs Are Too Expensive
Other Prescript Drug Coverage
Enrolling or Dropping a Prescription Drug Plan