To get the most out of your Medicare health benefits, you must understand how and when to enroll in Medicare. Unless you qualify for automatic enrollment, you will need to sign up for Medicare Part A and/or Part B during the Initial Enrollment Period (IEP) that begins three months before you turn 65 and lasts for seven months.

Automatic Enrollment For Original Medicare

Initial enrollment in Original Medicare, Part A and/or Part B, occurs automatically if you are turning 65 and already getting Social Security or Railroad Retirement Benefits (RRB) benefits or will start collecting retirement at age 65. You will need to sign up for Medicare Part B when you apply for retirement benefits, and Medicare Part A enrollment occurs automatically if you are eligible for Social Security retirement. A Medicare card will be mailed out about three months before your 65th birthday.

Medicare Part B comes with a monthly premium, while most people get Part A premium-free as long as they have worked at least 10 years (or 40 quarters) and paid Medicare taxes. Because Medicare Part B has a premium, some people may choose to delay enrollment if they are already covered under a different plan, such as an employer group plan.

Keep in mind that if you do not sign up for Medicare Part B when you are first eligible and sign up later, you may have to pay a late enrollment penalty for the duration that you have Medicare. If you delay Medicare Part B enrollment because of coverage under a current employer (either your own or your spouse's), you can qualify for a Special Enrollment Period when this group coverage ends and will not be subject to the penalty.

Medicare enrollment is also automatic if the person has been entitled to specific Social Security and Railroad Retirement Board (RRB) disability benefits for at least 24 months. A Medicare card is mailed out about three months before the 25th month of disability benefits. 

Beneficiaries with amyotrophic lateral sclerosis (ALS, also known as Lou Gehrig's disease) will automatically be enrolled in Medicare Part A and Part B starting in the month that their disability benefits begin.

If you have end-stage renal disease (ESRD), you do not need to be receiving Social Security disability benefits to qualify for Medicare and can still be working. If you have ESRD and require kidney dialysis or a kidney transplant, you can enroll in Original Medicare at any time before turning 65.

When To Enroll In Medicare

If you aren't receiving Social Security or RRB benefits when you turn 65, you will have to sign up for Medicare Part A and/or Part B during your Initial Enrollment Period (IEP). This enrollment period begins three months before your 65th birthday includes the month that you turn 65, and ends three months later. 

You can enroll in Medicare during your IEP, even if you do not plan to begin receiving retirement at age 65. When you apply through Social Security, there is an option to apply for Medicare only. You can sign up to receive Social Security retirement at a later time. 

If you do not qualify for retirement benefits because you have not worked long enough, you can still enroll in Medicare Part A and/or Part B during your IEP. You may not qualify for premium-free Medicare Part A, and the cost of your premium will vary depending on how long you worked and paid Medicare taxes. If you sign up for Medicare Part B, you will have to pay a monthly premium for Part B as well.

If you miss your initial enrollment for whatever reason, you can sign up for Medicare Part A and/or Part B during the General Enrollment Period that runs from January 1st through March 31st of every year. You might have to pay a late enrollment penalty for both Part A and Part B if you did not sign up when you were first eligible. You can also make changes to your coverage during general enrollment. 

You can sign up for Original Medicare, Part A, and Part B, through Social Security:

• By visiting www.ssa.gov
• By calling 1-800-772-1213 (TTY users 1-800-325-0778), Monday through Friday, from 7 AM to 7 PM.
• By visiting your local Social Security office.

If you worked at a railroad, contact the Railroad Retirement Board to enroll in Medicare Part A and/or Part B. You can call the RRB at 1-877-772-5772, Monday through Friday, 9 AM to 3:30 PM; TTY users can call 1-312-751-4701.

Once you enroll in Medicare, you will receive a red, white, and blue Medicare card showing whether you have Medicare Part A, Medicare Part B, or both. Please keep your card in a safe place so you will have it when you need it. If your card is ever lost or stolen, you can apply for a replacement card or call Social Security's toll-free number, 1-800-772-1213 (TTY users 1-800-325-0778), Monday through Friday, from 7 AM to 7 PM.

When Medicare Coverage Begins

If you are already receiving retirement benefits before turning 65, your Medicare coverage will start with the month you're first eligible (at age 65). If you sign up during the general enrollment, your coverage will not begin until July 1st.

If you are receiving disability benefits through Social Security or the RRB, your effective date is determined by the Social Security Administration or the Railroad Retirement Board. 

If you sign up for Medicare Part A and/or Part B during your Initial enrollment, the start of your coverage will depend on which month of IEP you signed up. The following chart shows when your Medicare coverage becomes effective if you enroll during your IEP: