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Medicare coverage typically starts when people turn 65. But if they're still working and receiving health insurance from an employer with 20 or more employees, they can delay their start to Medicare. People are automatically enrolled if they’re receiving Social Security benefits. Otherwise, they must enroll themselves.
Original Medicare includes Medicare Part A, which covers hospitals, and Medicare Part B, which covers doctor visits and outpatient services. Most people get premium-free Medicare Part A, while Medicare Part B requires paying monthly premiums.
Once enrolled, you can choose to buy additional private insurance, which includes Part D prescription drug plans, Medicare supplement or “Medigap” policies and Medicare Advantage plans — also known as Medicare Part C. Medicare Advantage plans, which bundle the parts of Medicare, include all the benefits of Parts A and B and usually Part D as well, but you must still enroll in Medicare Parts A and B and pay your monthly Part B premium.
Medicare age and eligibility
People are eligible for Medicare when they're 65 or older, or younger and living with certain disabilities. Medicare is also available for people with end-stage renal disease or with Lou Gehrig’s disease, also known as ALS. Medicare start dates vary depending on how you’re eligible.
When Medicare starts: Turning 65
Medicare coverage can start as early as the first day of the month in which you turn 65, unless you were born on the first of the month. In that case, your coverage can begin on the first day of the previous month.
People who are automatically enrolled will get coverage as soon as it’s available. Generally, you're automatically enrolled only if you claimed Social Security benefits early. If you have to enroll yourself, you should sign up in the three months before your birthday. While you have seven months around your birthday to enroll for the first time, that's not the same as having coverage. The three months before and after your birthday month, plus your birthday month, is what’s known as your initial enrollment period. But waiting until your birthday month or the three months afterward to sign up delays the start of your coverage and you're fully responsible for any health care costs you incur until your Medicare coverage begins.
When Medicare starts: People living with certain disabilities
Medicare also covers certain people under 65 who have disabilities severe enough that they qualify for Social Security Disability Insurance, or SSDI. Here’s when their Medicare coverage starts:
People who get disability benefits from Social Security automatically receive Medicare coverage after 24 months.
People who have ALS automatically receive Medicare coverage the same month that disability benefits start.
People who have end-stage renal disease usually can apply for Medicare starting on the first day of the fourth month of dialysis treatments. However, there are several additional conditions and opportunities to start Medicare at different points. And if they’re getting a kidney transplant, Medicare coverage can start the month they’re admitted to a hospital for the transplant if the transplant happens that month or within the next two months. Transplant delays may move Medicare’s starting date out, too.
When Medicare starts: General enrollment period
If you miss your initial enrollment period, you can sign up for premium-free Part A anytime, but you must wait until Medicare’s general enrollment period, Jan. 1 to March 31, to sign up for the other parts — unless you have a special enrollment period. Coverage starts July 1. Those who miss the initial enrollment period for Part B and Part D usually have to pay permanently higher premiums due to penalties.
When Medicare starts: Special enrollment periods
You can qualify for a special enrollment period and avoid penalties in a few circumstances, such as when you’re covered by a group health insurance plan from a current employer with 20 or more employees — either your own or your spouse’s. In this case, the clock starts ticking when the employment or the coverage ends, whichever comes first.
Then, you have two months to enroll in Medicare Advantage or Part D and eight months to enroll in Medicare Part B. (Though if you enroll in a Medicare Advantage plan, you’ll have to enroll in Part B at that time.) If you apply using a special enrollment period and your application is approved, your coverage starts either the first day of the month that you applied or the first day of the following month, depending on the situation.
Medicare effective date
The date your coverage starts will depend on when you sign up for Medicare:
When you sign up
When your Medicare coverage starts
Before the month of your 65th birthday.*
The month you turn 65.
The month you turn 65.
The next month.
One month after you turn 65.
Two months after you sign up.
Two or three months after you turn 65.
Three months after you sign up.
During the general enrollment period, which runs Jan. 1 to March 31 each year.
During a special enrollment period.
The next month.
*If your birthday is on the first of the month, your coverage will start on the first day of the month before your birthday month. For example, if you turn 65 on Aug. 1, your coverage will start on July 1.