Medicare starts on the first day of the month you turn 65, or the first day of the month you become may be able to access due to disability or end-stage renal disease

If you turn 65 on any day of the month, your coverage begins on the first of that same month — not on your birthday. If you turn 65 on March 15, Medicare Part A and Part B start March 1. If you turn 65 on March 1, coverage still starts March 1. The only exception is if you delay enrollment past 65, which moves your start date forward.

For people under 65 who become may be able to access because of a disability information or end-stage renal disease, Medicare begins the first day of the month you meet the medical criteria, not the day you file or the day Social Security approves your claim. The timing depends on when the Social Security Administration or Railroad Retirement Board officially recognizes your condition, which can take months after you first explore.

Key Takeaways

  • Medicare Part A and Part B coverage begins on the first day of the month you turn 65, regardless of which day of the month your birthday falls on.
  • If you enroll during your Initial Enrollment Period (the three months before, the month of, and three months after you turn 65), your coverage starts the first of the month you turn 65 with no penalty.
  • If you delay enrollment past your Initial Enrollment Period, your coverage start date moves forward and you may pay a permanent penalty on your premiums.
  • For people under 65 with disability or end-stage renal disease, Medicare begins the first day of the month Social Security officially recognizes your condition.
  • You must be a U.S. citizen or permanent resident and have lived in the United States for at least five consecutive years to be covered.

What happens if you enroll during your Initial Enrollment Period

Your Initial Enrollment Period is a seven-month window: three months before the month you turn 65, the month you turn 65, and three months after. If you enroll during this window, your Part A and Part B coverage starts on the first day of the month you turn 65, with no waiting period and no penalty.

Most people do not need to take any action during this period if they are already receiving Social Security benefits — Medicare enrolls them automatically. If you are not yet receiving Social Security, you should contact Social Security or visit your local Social Security office to enroll in Medicare. You can also enroll online at Medicare.gov or by calling 1-800-MEDICARE.

The exact dates of your Initial Enrollment Period depend on your birth month. If you were born on the 15th or later in any month, your Initial Enrollment Period begins four months before that month. If you were born on the 1st through 14th, it begins three months before. Social Security will send you a notice with your specific dates.

What happens if you miss your Initial Enrollment Period

If you do not enroll in Medicare Part A or Part B during your Initial Enrollment Period and you do not have other health coverage that counts as "creditable coverage," your coverage will not start until the first day of the month after you enroll. You will also pay a late enrollment penalty for as long as you have Medicare.

The penalty for Part B is 10 percent of the standard premium for each full 12 months you were may be able to access but not enrolled. If the standard Part B premium is $164.90 per month and you were may be able to access for three years without enrolling, your penalty would be 30 percent added to your premium permanently. The penalty for Part A works the same way, though fewer people pay it because Part A is usually free.

The only way to avoid this penalty is to show that you had creditable coverage — health insurance from an employer, a spouse's employer, TRICARE, the Veterans Health Administration, or another source that is at least as good as Medicare. You will need to provide proof of that coverage when you enroll.

How to enroll before your coverage start date

You can enroll in Medicare up to three months before the month you turn 65. Enrolling early does not change your start date — coverage still begins the first of the month you turn 65 — but it ensures your paperwork is processed in time and you receive your Medicare card before coverage begins.

To enroll, you have three options: go online to Medicare.gov and select "Sign Up for Medicare," call Social Security at 1-800-772-1213, or visit your local Social Security office in person. If you are already receiving Social Security retirement or disability benefits, you do not need to do anything — Social Security will enroll you automatically about three months before you turn 65.

When you enroll, have your Social Security number, birth date, and citizenship or permanent resident status ready. The process takes about 10 minutes online or on the phone. You will receive your Medicare card in the mail within two to four weeks. If your birthday is coming up within a month and you have not received your card, call 1-800-MEDICARE to check the status.

Special enrollment periods that change your start date

If you miss your Initial Enrollment Period but you had creditable coverage from an employer or union when you turned 65, you may be able to enroll in a Special Enrollment Period without paying a late penalty. This period usually lasts eight months after your creditable coverage ends. Your coverage will start the first of the month after you enroll, not the first of the month you turned 65.

You must be able to prove you had creditable coverage. Your employer or union should provide a letter stating the dates of coverage and confirming it was at least as good as Medicare. Without this letter, Medicare will assume you did not have creditable coverage and will explore the late penalty.

Other events that open a Special Enrollment Period include losing employer coverage due to retirement, losing coverage because your employer went out of business, or aging off a parent's health plan. Each situation has different rules about when you can enroll and when coverage starts. Call 1-800-MEDICARE to find out whether your situation qualifies.

Medicare coverage for people under 65 with disability

If you are approved for Social Security Disability Insurance (SSDI), Medicare coverage begins 24 months after your disability benefits start, not when you are first approved. If Social Security approves your claim retroactively — meaning they say your disability began in the past — the 24-month clock starts from that retroactive date, not from the approval date.

For example, if Social Security approves your disability claim in June 2024 but says your disability began in January 2024, your Medicare coverage will start in January 2026 (24 months after January 2024). You will receive your Medicare card in the mail about one month before coverage begins.

If you are approved for Railroad Retirement Disability benefits instead of Social Security, the same 24-month waiting period applies. The Railroad Retirement Board will notify you of your Medicare start date once your disability is approved.

Medicare coverage for people with end-stage renal disease

If you have end-stage renal disease (ESRD) — permanent kidney failure requiring dialysis or a transplant — you become may be able to access for Medicare regardless of age. Your coverage begins the first day of the month you start dialysis treatment or the month you have a kidney transplant, whichever comes first.

If you receive a pre-emptive transplant (a transplant before you start dialysis), coverage begins the first day of the month of your transplant. You do not have to wait for dialysis to start. You must notify Social Security or the Railroad Retirement Board of your ESRD diagnosis so they can process your Medicare enrollment. Your doctor's office can help you report this to Social Security.

What to do before your coverage start date

Once you know your Medicare start date, contact your current health insurance provider to find out when to cancel that coverage. If you cancel too early, you may have a gap in coverage. If you cancel too late, you may pay premiums for overlapping coverage. Most people should cancel their old coverage effective the last day of the month before Medicare starts.

If you have prescriptions you take regularly, ask your doctor or pharmacist whether your medications are covered under Medicare Part D (prescription drug coverage). You can view the formulary — the list of covered drugs — for any Part D plan on Medicare.gov. If your current medications are not covered, you may need to switch to a different medication or choose a different Part D plan.

Request your medical records from your current doctors and bring them to your first appointment after Medicare starts. This helps your new providers understand your health history. If you are switching doctors because your current doctor does not accept Medicare, ask for a referral to a Medicare-accepting provider in your area.

Frequently Asked Questions

Can I start Medicare before I turn 65?

No, unless you have a disability or end-stage renal disease. If you have neither, you cannot enroll in Medicare until the month you turn 65. Enrolling early during your Initial Enrollment Period does not change your start date — it only ensures your paperwork is processed in time.

What if I turn 65 but I am still working?

You should still enroll in Medicare during your Initial Enrollment Period, even if you are still working and have employer coverage. If you delay enrollment, you will pay a permanent late penalty when you eventually enroll. The only exception is if your employer has 20 or more employees — then you can delay Part B without penalty as long as you are actively employed.

Will I receive my Medicare card before my coverage starts?

Usually yes. Medicare cards are mailed about two to four weeks after you enroll. If your birthday is coming up within a month and you have not received your card, call 1-800-MEDICARE. Your coverage starts on schedule even if your card has not arrived yet — you can use your Social Security number as proof of coverage at the doctor's office.

What if I am not a U.S. citizen?

You must be a U.S. citizen or a permanent resident who has lived in the United States for at least five consecutive years to be covered by Medicare. If you are a permanent resident, bring your green card when you enroll. If you do not meet these requirements, you cannot enroll in Medicare.

Can I change my Medicare start date once I enroll?

No. Your start date is determined by when you turn 65 or when you become may be able to access due to disability or ESRD. Once coverage begins, you cannot move it backward or forward. If you enrolled late and your coverage starts later than the first of the month you turned 65, that is your permanent start date.