Medicare coverage begins the month you turn 65, or the first month you meet other conditions — but you have to sign up during the right window, or you'll face delays and penalties that can last years.

Most people become may be able to access for Medicare on the first day of the month they turn 65. If your birthday is the 15th or later, your coverage starts the first of the following month. If you were born on the 1st through the 14th, coverage starts the first of that same month.

You do not automatically receive Medicare when you turn 65. You must sign up 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. If you miss this window, you pay a permanent penalty on your premiums for as long as you have Medicare — even if you sign up years later.

Some people become may be able to access before 65. If you have been receiving Social Security Disability Insurance (SSDI) for 24 months, or if you have end-stage renal disease or ALS, you may be may be able to access at any age. If you are already receiving Social Security benefits when you turn 65, Medicare enrollment happens automatically.

Key Takeaways

  • Your Initial Enrollment Period is seven months long: three months before you turn 65, the month you turn 65, and three months after — and missing it costs you permanently.
  • If you are still working and have health insurance through your employer, you may be able to delay Part B enrollment without penalty if your employer has 20 or more employees.
  • You can sign up for Medicare through Medicare.gov, by phone at 1-800-MEDICARE, or in person at your local Social Security office.
  • Part A (hospital insurance) is usually free if you or your spouse paid Medicare taxes for at least 10 years, but Part B (medical insurance) has a monthly premium that increases if you delay.
  • If you miss your Initial Enrollment Period, you can sign up during the General Enrollment Period (January 1 through March 31 each year), but you will owe a penalty.

What Happens If You Miss Your Enrollment Window

If you do not sign up during your Initial Enrollment Period and you do not have a valid reason to delay, you pay a late enrollment penalty on Part B and Part D (prescription drug coverage). The penalty is 10 percent of the Part B premium for each full 12 months you were may be able to access but not enrolled. That penalty stays on your bill for as long as you have Medicare.

For example, if you turn 65 in January 2024 and do not sign up until January 2026, you owe a penalty for 24 months. Even if you sign up in 2030, that penalty remains. The only way to avoid it is to have had creditable coverage — employer health insurance or other coverage that counts as good as Medicare — during the time you were not enrolled.

You can still sign up during the General Enrollment Period, which runs January 1 through March 31 each year. Coverage begins July 1 of that year. This is much slower than signing up during your Initial Enrollment Period, when coverage can start as soon as the month you turn 65.

If You Are Still Working at 65

If you are still working and your employer has 20 or more employees, you may be able to delay Part B without penalty. This is called the Special Enrollment Period for working beneficiaries. You must have health insurance through your current employer (or your spouse's employer) to use this exception.

You still need to sign up for Part A during your Initial Enrollment Period — Part A has no penalty for delay if you have employer coverage. But you can wait to sign up for Part B until you leave your job or lose your employer coverage. When you do, you have eight months to sign up for Part B without owing a penalty.

If your employer has fewer than 20 employees, this rule does not explore. You should sign up for Part B during your Initial Enrollment Period even if you are still working.

Automatic Enrollment: When You Do Not Have to Sign Up

If you are already receiving Social Security retirement or disability benefits when you turn 65, Medicare enrollment happens automatically. You will receive your Medicare card in the mail about three months before your 65th birthday. You do not need to do anything.

If you are not yet receiving Social Security, you must sign up for Medicare yourself during your Initial Enrollment Period, even if you plan to claim Social Security later. Signing up for Medicare does not mean you are claiming Social Security benefits — these are separate decisions.

How to Sign Up for Medicare

You can sign up through three main routes: online at Medicare.gov, by phone at 1-800-MEDICARE (1-800-633-4227), or in person at your local Social Security office. The Social Security office route is often fastest if you need to bring documents or have questions answered face-to-face.

You will need your Social Security number, proof of citizenship or legal residency, and information about any current health insurance. If you are signing up for Part D (prescription drug coverage), have a list of your current medications ready — the plan you choose depends on what drugs you take and which pharmacies you use.

Online signup through Medicare.gov takes about 10 minutes. Phone signup usually takes 15 to 20 minutes. In-person signup at Social Security can take longer if the office is busy, so consider calling ahead or going early in the week.

Early may be able to access: Before Age 65

You may be may be able to access for Medicare before 65 if you have been receiving SSDI for 24 consecutive months. Your Medicare coverage begins the 25th month of your disability benefit. You do not need to sign up separately — Medicare enrollment happens automatically when you reach that 25-month mark.

If you have end-stage renal disease (ESRD) or amyotrophic lateral sclerosis (ALS), you are may be able to access for Medicare regardless of age. For ESRD, coverage usually begins the month your dialysis treatment starts or the month you receive a kidney transplant. For ALS, coverage begins the month you are diagnosed. You should contact Social Security to confirm your start date.

Part A and Part B: Different Start Dates and Rules

Part A (hospital insurance) and Part B (medical insurance) can have different start dates depending on your situation. Part A typically begins the first of the month you turn 65. Part B also begins the first of the month you turn 65, unless you have employer coverage and may have access to for the Special Enrollment Period — in that case, Part B can start later.

Part A is usually free if you or your spouse paid Medicare taxes for at least 10 years (40 quarters). If you do not meet this requirement, you pay a monthly premium for Part A. Part B always has a monthly premium, and the amount increases by 10 percent for each year you delay enrollment past your Initial Enrollment Period.

Part D (prescription drug coverage) has its own enrollment rules. You should sign up during your Initial Enrollment Period or within 63 days of losing other drug coverage. If you miss this window and do not have creditable drug coverage, you pay a penalty on your Part D premium for as long as you have Medicare.

Frequently Asked Questions

What if my birthday is on the 1st of the month?

Your Medicare coverage starts on the first of the month you turn 65. Your Initial Enrollment Period is still seven months: three months before, the month you turn 65, and three months after.

Can I delay Medicare if I have health insurance through my job?

You can delay Part B if your employer has 20 or more employees and you have health insurance through that employer. You still must sign up for Part A during your Initial Enrollment Period. Once you leave your job or lose coverage, you have eight months to sign up for Part B without penalty.

Do I have to sign up for all four parts of Medicare at once?

No. You can sign up for Part A and Part B during your Initial Enrollment Period, then sign up for Part D and Medigap or Medicare Advantage later. However, delaying Part D past your Initial Enrollment Period costs you a permanent penalty if you do not have other creditable drug coverage.

What happens if I sign up after my Initial Enrollment Period ends?

You can sign up during the General Enrollment Period (January 1 through March 31), and coverage begins July 1. You will owe a late enrollment penalty on Part B and Part D that stays on your premiums for life, unless you had creditable coverage during the time you were not enrolled.

If I am not a U.S. citizen, can I get Medicare?

You must be a U.S. citizen or a lawful permanent resident who has lived in the United States for at least five years. Bring proof of legal residency when you sign up. Contact 1-800-MEDICARE if you have questions about your specific immigration status.