You can start Medicare at 65, but the exact month depends on your birthday and when you sign up

Medicare may be able to access begins the month you turn 65, regardless of whether you are still working. However, your coverage does not start automatically — you have to take action during a specific window, or you may face delays and late-enrollment penalties that can raise your premiums permanently.

If you are already receiving Social Security benefits when you turn 65, Medicare enrollment happens automatically and your coverage starts the first day of the month you turn 65. If you are not yet receiving Social Security, you must sign up yourself during your Initial Enrollment Period, which runs for seven months: three months before the month you turn 65, the month you turn 65, and three months after.

Missing this window does not lock you out permanently, but it does cost money. For every 12 months you delay past 65 without a valid reason, your Part B premium increases by 10 percent for as long as you have Medicare. The same penalty applies to Part D (prescription drug coverage) if you go 63 or more days without coverage.

Key Takeaways

  • Medicare starts the month you turn 65, but you must sign up during your seven-month Initial Enrollment Period or face permanent premium increases.
  • If you receive Social Security, Medicare enrollment is automatic; if not, you sign up through Medicare.gov, by phone, or at your local Social Security office.
  • Delaying enrollment past 65 costs 10 percent more per year on Part B premiums and the same on Part D, with no way to remove the penalty later.
  • You may be able to delay without penalty if you are still working and covered by your employer's health plan, but you must meet specific conditions and notify Medicare.

How the enrollment timeline works if you are turning 65

Your Initial Enrollment Period is seven months long and centers on your birth month. If you turn 65 in June, your enrollment window opens in March and closes in September. During this time, you can sign up for Part A (hospital insurance) and Part B (medical insurance) without waiting or paying extra.

The easiest way to enroll is online at Medicare.gov. You can also call 1-800-MEDICARE (1-800-633-4227) or visit your local Social Security office in person. Have your Social Security number and proof of citizenship or legal residency ready. The process takes about 15 minutes online.

If you miss your Initial Enrollment Period, you can still sign up during the General Enrollment Period, which runs January 1 through March 31 each year. Coverage would not start until July 1 of that year, leaving you uninsured for months. The 10 percent annual premium penalty on Part B also applies and stays on your bill for life.

When you can delay enrollment without a penalty

You can postpone Medicare Part B and Part D past 65 without penalty if you are still working and covered by your employer's health plan. This is called creditable coverage. Your employer's plan must be based on current employment — coverage for a spouse or retiree plan does not count.

To use this exception, you must actively choose not to enroll in Part B during your Initial Enrollment Period. straightforward not signing up is not enough; you need to tell Medicare you are declining because you have employer coverage. You can do this when you call to enroll in Part A, or by submitting a form to Medicare directly.

Once you leave your job or lose the employer coverage, you have eight months to sign up for Part B without penalty. This is called your Special Enrollment Period. If you wait longer than eight months, the 10 percent penalty kicks in. Keep records of your employment dates and coverage details in case Medicare questions your timeline later.

What happens if you miss the enrollment window

If your Initial Enrollment Period ends and you have not signed up, you are not automatically covered. You can still enroll during the General Enrollment Period (January 1 through March 31), but coverage does not start until July 1. You will have no Medicare coverage from the time you turn 65 until July 1 of the following year.

During that gap, you are responsible for all medical costs. If you have an accident or illness, you pay out of pocket unless you have other insurance. Many people in this situation face large bills and then face the permanent premium increase on top of it.

The 10 percent penalty on Part B applies for every 12 months you go without coverage after your Initial Enrollment Period ends. If you delay two years, your premium is 20 percent higher. If you delay five years, it is 50 percent higher. This penalty never goes away, even if you eventually sign up.

Part D (prescription drug) enrollment and timing

Part D enrollment follows the same seven-month Initial Enrollment Period as Part A and Part B. If you do not sign up during this window and you do not have other creditable prescription drug coverage, you pay a 1 percent monthly penalty on top of your Part D premium for every month you were without coverage.

Unlike Part B, the Part D penalty is calculated differently: it is based on the national average Part D premium at the time you enroll, multiplied by the number of months you were uninsured. This penalty also stays with you for life. If you have coverage through your employer or a retiree plan, that counts as creditable coverage and you can delay Part D without penalty, but you must document it.

When you do enroll in Part D, bring a list of all medications you take, including over-the-counter drugs. Different plans cover different drugs at different costs, and choosing the wrong plan can cost hundreds of dollars per year.

Special situations: disability, ESRD, and ALS

You can start Medicare before 65 if you have been receiving Social Security Disability Insurance (SSDI) for 24 months. Medicare coverage begins automatically in the 25th month of your disability benefits. You do not need to do anything — Social Security handles the enrollment.

If you have End-Stage Renal Disease (ESRD) or Amyotrophic Lateral Sclerosis (ALS), you can start Medicare when ready, regardless of age. For ESRD, coverage begins the first day of the month you start dialysis or receive a kidney transplant. For ALS, coverage begins the first day of the month you are diagnosed. You must still sign up; call 1-800-MEDICARE to start the process.

These exceptions are rare, but if they explore to you, do not wait. Enroll as soon as you learn you may have access to. The rules are different from standard Medicare enrollment, and missing the window can still create coverage gaps.

Coordinating Medicare with employer coverage

If you are still working at 65 and your employer has 20 or more employees, your employer's health plan is the primary payer and Medicare is secondary. You can delay Part B without penalty, but you should still enroll in Part A (hospital insurance) at 65, even if you do not use it yet. Part A has no monthly premium if you or your spouse paid Medicare taxes for 10 years.

When you retire or lose your job, notify Medicare within 60 days. You then have eight months to enroll in Part B without penalty. If you wait longer, the 10 percent penalty applies. Some employers offer retiree health plans; these do not count as creditable coverage for Part B purposes, so you still need to enroll in Part B by 65 or face a penalty.

Keep copies of your employer's plan documents and your enrollment letters. If Medicare later questions whether your coverage was creditable, you will need proof that it met Medicare's standards.

Frequently Asked Questions

What if I turn 65 in the middle of the month?

Medicare coverage starts on the first day of the month you turn 65, regardless of the date within that month. If you turn 65 on June 15, your coverage begins June 1. Your enrollment window still opens three months before and closes three months after your birth month.

Do I have to enroll in Part B if I only want Part A?

No. Part A and Part B are separate. You can enroll in Part A only and delay Part B if you have employer coverage. However, if you delay Part B past your Initial Enrollment Period without creditable coverage, you will pay a 10 percent penalty when you do enroll. Document your reason for delaying in writing to Medicare.

Can I change my mind if I enrolled in Medicare by mistake?

Yes, but only within a limited time. You have 14 calendar days from the date you receive your Medicare card to request disenrollment. After that, you are locked in until the next General Enrollment Period (January 1 through March 31). If you have creditable employer coverage, contact Medicare when ready to explain and request removal.

What if I am still working and do not want Medicare at 65?

You can decline Part B if you have employer coverage, but you should still enroll in Part A. Part A is free if you paid Medicare taxes for 10 years, and it covers hospital stays. When you leave your job, you have eight months to enroll in Part B without penalty. After eight months, the 10 percent penalty applies permanently.

Does my spouse have to enroll at the same time?

No. Each person has their own Initial Enrollment Period based on their own birth month. Your spouse's enrollment window may be months before or after yours. Each of you must sign up separately during your own seven-month window to avoid penalties.