Your Guide to Medicare Enrollment Periods

Calendar page with female hand holding pen on desk table

A common Medicare question is, When can I enroll?

Medicare is health insurance for people 65 and older (and people younger than 65 who have a disability or other qualifying condition) — but your 65th birthday is not the only time you can change your enrollment.

There are several different periods that allow you to make changes. “Changes” may include:

  • Enrolling in Medicare for the first time
  • Switching from Original Medicare to a Medicare Advantage plan, or vice versa
  • Switching from one Medicare Advantage plan to another
  • Joining, switching, or dropping a Part D drug plan


Initial Enrollment Period (IEP)

This is the big one, because for many, it’s your earliest opportunity to enroll in Medicare. Your Initial Enrollment Period is a seven-month window to enroll in Medicare that includes:

  • The 3 months before the month of your 65th birthday
  • Your birthday month
  • The 3 months after your 65th birthday month

Note: If your birthday falls on the 1st of the month, Medicare treats it as if your birthday took place in the previous month — for example, if your birthday is on June 1, Medicare considers May your birthday month.

  • Who enrolls during this period? If you receive health coverage through an employer and are retiring at 65, you will likely sign up for Medicare during this time. If you enroll during your IEP, you have 3 months to change to another Medicare Advantage plan or go back to Original Medicare.  

Annual Enrollment Period (AEP)

The Medicare Annual Enrollment Period runs each year from October 15 to December 7. When you enroll in Medicare during this period, coverage begins January 1 of the following year. 

  • Who enrolls during this period? Anyone who is eligible for Medicare — including those who are enrolling for the first time and those who are already enrolled in Medicare — may enroll or make changes (drop or switch) to their current enrollment. 

Open Enrollment Period

This enrollment period runs from January 1 to March 31. It allows people who enrolled in a Medicare Advantage plan during AEP to make changes — such as switching to another Medicare Advantage plan or going back to Original Medicare.

  • Who enrolls during this period? Anyone who is already enrolled in a Medicare Advantage plan can make changes. You may not join Original Medicare or a Medicare Advantage plan for the first time during this period. 

Special Enrollment Period

When you experience a qualifying life event— such as a change of address or a loss of your current coverage — you’re eligible for a Special Enrollment Period (SEP). Generally, these vary in length depending on the exact SEP you qualify for. For full details, see this list of SEPs on

  • Who enrolls during this period? There are many reasons someone may enroll in Medicare or make changes to their Medicare enrollment during an SEP. Here are some common examples:
    • You worked past the age of 65 and receive health insurance through your employer, but are now retiring.
    • You are 65 or older and receive health insurance through your spouse, who is now retiring.
    • You moved to a new address that isn’t in your Medicare Advantage plan’s area of service.
    • You moved back to the U.S. after living abroad.
    • You became eligible for, or lost your eligibility for, Medicaid. 
    • You qualify for Extra Help or a State Pharmaceutical Assistance Program.

These are not the only qualifying events. For more scenarios, see this list on