When does Medicare start?

Medicare coverage typically begins at the age of 65. However, if they have health insurance through an employer (or a spouse's employer) with 20 or more employees, they can postpone their enrollment in Medicare. People who receive Social Security benefits are automatically enrolled. Otherwise, they will have to enroll themselves.

Medicare Part A, which covers hospitals, and Medicare Part B, which covers doctor visits and outpatient services, are both part of original Medicare. Most people receive premium-free Medicare Part A, whereas Medicare Part B requires monthly premium payments.

Once enrolled, you have the option of purchasing additional private insurance, such as Part D prescription drug plans, Medicare Supplement or Medigap policies, and Medicare Advantage plans, also known as Medicare Part C. Medicare Advantage plans, which combine Medicare Parts A and B, usually include Part D benefits 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 if they are 65 or older, or if they are younger than 65 and have certain disabilities. Medicare is also available to those suffering from end-stage renal disease or Lou Gehrig's disease, also known as ALS. Medicare start dates differ depending on how you qualify.

When Medicare starts: Turning 65

Unless you were born on the first of the month, Medicare coverage can begin as early as the first day of the month in which you turn 65. In that case, your coverage can begin on the first of the month preceding.

If you have already claimed Social Security benefits, you are generally automatically enrolled in Medicare at the age of 65.

If you must enroll yourself, you should do so three months before your birthday to avoid coverage gaps. Your initial enrollment period includes your 65th birthday month, as well as the three months preceding and following it. However, if you enroll during your birthday month or the two to three months following, your coverage will not begin until the following month. (Enroll three months in advance, and coverage begins on the first day of your birthday month.)

When Medicare starts: People living with certain disabilities

Medicare also covers people under the age of 65 who have severe enough disabilities to qualify for Social Security Disability Insurance, or SSDI. When does their Medicare coverage begin?

• People who receive Social Security disability benefits automatically receive Medicare coverage after 24 months.
• People with ALS are automatically enrolled in Medicare the month their disability benefits begin.
• End-stage renal disease patients can typically apply for Medicare on the first day of the fourth month of dialysis treatment. However, there are a number of additional conditions and opportunities to begin Medicare at various points. If they need a kidney transplant, Medicare coverage can begin the month they are admitted to a hospital for the transplant, as long as the transplant occurs that month or within the next two months. Delays in transplants may also push Medicare's start date back.

When Medicare starts: General enrollment period

If you miss your initial enrollment period, you can sign up for premium-free Part A at any time, but you must wait until Medicare's general enrollment period, which runs from January 1 to March 31 — unless you have a special enrollment period. Coverage begins the month you sign up. Those who miss the initial enrollment period for Part B and Part D usually have to pay higher premiums for the rest of their lives due to penalties.

When Medicare starts: Special enrollment periods

You may be eligible for a special enrollment period and avoid penalties if you are covered by a group health insurance plan from a current employer with 20 or more employees — either your own or your spouse's. In that case, the clock begins to tick when either the employment or the coverage ends, whichever comes first. (Please keep in mind that COBRA and retiree health coverage do not extend the clock.)

You have two months to enroll in Medicare Advantage or Part D, and eight months to enroll in Medicare Part B at that point. (However, if you enroll in a Medicare Advantage plan, you must also enroll in Part B.) If you apply during a special enrollment period and your application is approved, your coverage will begin on the first of the month following.

Missing a chance to sign up because of a natural disaster, or missing a chance to enroll because a health plan or employer provided incorrect information, may also qualify you for a SEP. Fill out the Application for Medicare Part A and Part B Special Enrollment Period and fax or mail it to your local Social Security office to apply for a SEP.

Medicare start date

Your coverage will begin on the date you sign up for Medicare:

The coverage always begins on the first of the month. If you are unsure about when you can sign up for Medicare, contact Medicare directly.