Medicare starts on the first day of the month you turn 65, or the first day of the month after you meet other conditions

If you are turning 65, your Medicare Part A (hospital insurance) and Part B (medical insurance) coverage begins on the first day of that month, even if your birthday is on the 15th or the 30th. You do not have to wait until your actual birthday. The Social Security Administration automatically enrolls most people in Part A and Part B when they reach 65, as long as they are a U.S. citizen or permanent resident who has lived in the country for at least five years.

If you are under 65 and have received Social Security Disability Insurance (SSDI) for 24 months, Medicare begins on the first day of the 25th month of your disability. If you have end-stage renal disease (ESRD) or amyotrophic lateral sclerosis (ALS), you may be covered sooner — sometimes when ready — regardless of age. The exact start date depends on when the Social Security Administration or your dialysis center processes your case.

Key Takeaways

  • Medicare Part A and Part B start on the first day of the month you turn 65, and the Social Security Administration enrolls most people automatically.
  • If you are under 65 and have received SSDI for 24 months, Medicare begins on the first day of your 25th month of disability.
  • You can delay Part B enrollment past 65 without penalty only if you have employer health insurance through your job or your spouse's job.
  • If you miss the initial enrollment window and do not have employer coverage, you will pay a higher premium for Part B for as long as you have Medicare.
  • Part D (prescription drug coverage) and Part C (Medicare Advantage) have separate enrollment periods and start dates that differ from Part A and Part B.

Automatic enrollment at 65 and what happens next

The Social Security Administration sends you a Medicare card in the mail about three months before you turn 65. This card shows your Medicare number and which parts of Medicare you are enrolled in. Most people are automatically enrolled in Part A and Part B, but you have the right to decline Part B if you have health insurance through your employer or your spouse's employer. If you decline, you must sign and return a form to Social Security.

Your Medicare coverage becomes active on the first day of the month you turn 65. You do not need to do anything else to set up it — no phone call, no visit to an office. If you have already been receiving Social Security benefits, the transition is seamless. If you have not yet claimed Social Security, you can still receive Medicare at 65 even if you choose to delay your Social Security payments.

Enrollment important date if you are not automatically enrolled

Some people are not automatically enrolled in Part B. This includes people who are still working and have employer health insurance, people who are not yet receiving Social Security, and some non-citizens. If you fall into one of these groups, you have a seven-month Initial Enrollment Period (IEP) centered on the month you turn 65: three months before, the month itself, and three months after.

If you enroll in Part B during this window, your coverage starts on the first day of the month you enroll or the first day of the following month, depending on when in the month you sign up. If you miss this window and do not have employer coverage, you enter a General Enrollment Period (GEP) from January 1 to March 31 each year. Coverage from a GEP enrollment starts July 1 of that year. More importantly, you will pay a late enrollment penalty — a percentage increase to your Part B premium that stays with you permanently.

When Part D and Part C coverage begins

Part D (prescription drug coverage) and Part C (Medicare Advantage plans) are not automatic. You must enroll in them separately during the Initial Coverage Election Period (ICEP), which runs from three months before you turn 65 through two months after. If you enroll during this window, your coverage typically starts January 1 of the following year, even if you enroll in November or December.

If you miss the ICEP and go without Part D coverage, you will pay a late enrollment penalty on your Part D premium for as long as you have Medicare. The penalty is small each month but adds up over time. Part C has its own enrollment rules: you can switch plans or enroll during the Annual Enrollment Period (AEP) from October 15 to December 7 each year, with coverage starting January 1.

Special enrollment periods for life changes

If you experience certain life events — losing employer health insurance, moving out of your plan's service area, getting married, or becoming a U.S. citizen — you may be able to enroll in Medicare or change your coverage outside the normal enrollment windows. These Special Enrollment Periods (SEPs) usually last 60 or 63 days from the date of the event. You must report the event to Medicare and provide proof, such as a letter from your employer or a marriage certificate.

The start date of coverage from a SEP varies. If you lose employer coverage, for example, your Part B coverage may start the first day of the month after you enroll. If you move, your new plan coverage typically starts the first day of the month after your move. It is important to contact Medicare directly to confirm your start date, because missing the important date for a SEP can mean waiting until the next General Enrollment Period.

What to do if you are under 65 with SSDI or a may have access to condition

If you have been receiving SSDI for 24 months, Medicare Part A and Part B start automatically on the first day of your 25th month of disability. You do not need to enroll — the Social Security Administration handles this. You will receive your Medicare card in the mail before your coverage begins.

If you have end-stage renal disease, you may be covered as soon as you start dialysis or receive a kidney transplant, depending on your situation. If you have ALS, you are covered when ready upon approval of your SSDI claim, with no 24-month wait. In both cases, your dialysis center or the Social Security Administration will notify you of your start date. If you are unsure whether you may have access to under these conditions, contact Social Security at 1-800-772-1213 to confirm.

Delayed enrollment and coverage gaps

If you are still working at 65 and have health insurance through your job, you can delay Part B enrollment without penalty. This is called creditable coverage. When you finally leave your job and lose that insurance, you have eight months to enroll in Part B without paying a late penalty. Your coverage starts the first day of the month after you enroll.

If you miss this eight-month window, you will pay the late enrollment penalty. There is no way to waive or remove this penalty, even if you did not realize you were supposed to enroll. The penalty is 10 percent of the standard Part B premium for each full year you were may be able to access but not enrolled, and it applies for the rest of your life. This makes it critical to enroll as soon as your employer coverage ends.

Frequently Asked Questions

Does Medicare start on my birthday or the first of the month?

Medicare starts on the first day of the month you turn 65, not on your birthday itself. If you turn 65 on March 15, your coverage begins March 1. If you turn 65 on April 1, your coverage begins April 1.

What if I am still working at 65 — do I have to take Medicare?

You do not have to enroll in Part B if you have health insurance through your current job or your spouse's job. You can delay Part B without penalty as long as you have that employer coverage. When you leave your job, you have eight months to enroll in Part B without paying a late penalty.

Can I get Medicare before 65?

Yes, if you have received SSDI for 24 months, have end-stage renal disease, or have ALS. Otherwise, you must wait until 65. There is no way to lower the age requirement based on health status or income.

What happens if I miss my enrollment important date?

If you miss your Initial Enrollment Period for Part B and do not have employer coverage, you can enroll during the General Enrollment Period (January 1 to March 31), but your coverage will not start until July 1. You will also pay a permanent late enrollment penalty on your Part B premium. For Part D, a missed important date means a permanent penalty on your prescription drug premium.

Does my spouse get Medicare when I do?

No. Your spouse has their own enrollment timeline based on their own age or disability status. If your spouse is also 65, they enroll separately. If they are younger and not disabled, they must wait until they turn 65 or meet another condition for coverage.