When and how to enroll depends on your age and work history

You can enroll in Medicare starting three months before you turn 65, during the month you turn 65, and for three months after. This seven-month window is called your Initial Enrollment Period. If you enroll during this window, your coverage typically begins on the first day of the month you turn 65 (or the first of the following month if you enroll after your birthday month).

If you miss this window, you can still enroll, but you may pay a higher monthly premium for Part B and Part D for as long as you have Medicare — a permanent penalty called a late enrollment penalty. The only exception is if you had health coverage through your job or your spouse's job and did not need to enroll right away. In that case, you have a special enrollment period of eight months after that coverage ends.

You can enroll 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 Administration handles Medicare enrollment, even though Medicare is run by the Centers for Medicare & Medicaid Services (CMS).

Key Takeaways

  • Your Initial Enrollment Period runs for seven months: three months before you turn 65, the month you turn 65, and three months after.
  • Enrolling during this window means your coverage starts on the first of your birth month or the month after, with no premium penalty.
  • If you had job-based health coverage, you have an eight-month special enrollment period after that coverage ends to enroll without penalty.
  • You enroll through Social Security (online, by phone, or in person), not through Medicare directly.
  • Missing your enrollment window results in a permanent monthly penalty added to your Part B and Part D premiums for life.

What you need to have ready before you enroll

Gather your Social Security number, proof of citizenship or legal residency, and information about any current health coverage (from an employer, union, or spouse's plan). You will also need to know whether you are still working and, if so, the name of your employer.

If you are enrolling in a Medicare Advantage plan (Part C) or a prescription drug plan (Part D), have a list of your current medications and the pharmacies you use. This helps you check whether your plan covers what you take and where you can fill prescriptions.

Enrolling online at Medicare.gov

Go to Medicare.gov and click "Create an account" in the upper right corner. You will set up a username and password, then answer security questions. Once your account is created, you can start your enrollment by clicking "Enroll in Medicare" on the homepage.

The online form asks for your personal information, citizenship status, and whether you want Part A (hospital insurance), Part B (medical insurance), Part D (prescription drug coverage), or a Medicare Advantage plan instead of Part B and D. You can also decline coverage if you have job-based insurance and do not need Medicare yet — just make sure you understand the late enrollment penalty rules first.

After you submit, you will see a confirmation number on screen. Save or print it. You can also log back into your Medicare.gov account anytime to check the status of your enrollment or make changes during the annual open enrollment period (October 15 to December 7 each year).

Enrolling by phone with Social Security

Call 1-800-MEDICARE (1-800-633-4227) and tell the representative you want to enroll in Medicare for the first time. Have your Social Security number, citizenship information, and current health coverage details ready. The call usually takes 15 to 20 minutes.

The representative will ask the same questions as the online form: which parts of Medicare you want, whether you are still working, and whether you want a Medicare Advantage plan or Original Medicare (Part A and Part B) with a separate Part D plan. At the end of the call, you will receive a confirmation number by mail within two weeks.

If you speak a language other than English, interpreters are available. Tell the representative your language when you call, or use the relay service for deaf and hard-of-hearing callers.

Enrolling in person at Social Security

Visit your local Social Security office to enroll. You can find the nearest office at ssa.gov/locator or by calling 1-800-772-1213. Bring your Social Security card, proof of citizenship (passport, birth certificate, or naturalization papers), and information about your current health coverage.

A Social Security representative will walk you through the enrollment form in person. This option works well if you prefer face-to-face help or have questions that need detailed explanation. You will receive a confirmation number at the end of your visit.

Understanding Part A, Part B, Part D, and Medicare Advantage

Part A covers hospital stays, skilled nursing facility care, hospice, and some home health services. Most people do not pay a monthly premium for Part A if they or their spouse paid Medicare taxes while working. Part A has a deductible you pay when you are admitted to the hospital.

Part B covers doctor visits, outpatient care, lab tests, and medical equipment. Part B has a monthly premium (the standard amount is set each year by Medicare) and a yearly deductible. If your income is above a certain level, you pay a higher premium — this is called an Income-Related Monthly Adjustment Amount (IRMAA).

Part D covers prescription drugs. You choose a Part D plan from private insurance companies that contract with Medicare. Each plan has a different list of covered drugs, so compare plans based on your medications. Part D also has a monthly premium and a yearly deductible.

Medicare Advantage (Part C) is an alternative to Original Medicare. It is offered by private insurance companies and includes Part A, Part B, and usually Part D all in one plan. Many Medicare Advantage plans have low or zero monthly premiums but require you to use doctors and hospitals in their network. You cannot have both Original Medicare and Medicare Advantage at the same time.

What happens after you enroll

Once your enrollment is processed, Medicare will mail you a Medicare card within two weeks. Your card shows your Medicare number and which parts of Medicare you have. Keep it in a safe place and bring it to all doctor visits and hospital stays.

If you enrolled in Part D or Medicare Advantage, your insurance company will also send you information about your plan, including your member ID card, formulary (list of covered drugs), and network providers. Review these materials carefully so you know which pharmacies and doctors are in your plan.

Your coverage begins on the first day of the month you turn 65 (or the first of the following month if you enroll after your birthday month). If you enrolled during your Initial Enrollment Period, there is no waiting period. If you enrolled late, your coverage begins the first of the month after your enrollment is processed.

Frequently Asked Questions

What if I am still working and do not need Medicare yet?

You can delay enrolling in Part B and Part D without penalty if you have job-based health coverage through your current employer or your spouse's employer. You have eight months after that coverage ends to enroll without a late penalty. Tell Social Security or Medicare that you are still working when you enroll in Part A — this protects you from the Part B and Part D penalties.

Can I change my mind after I enroll?

Yes, but the timing matters. During your Initial Enrollment Period, you can make changes anytime. After that, you can change your coverage only during the annual open enrollment period (October 15 to December 7) or if you have a may have access to life event like losing job-based coverage or moving out of your plan's service area. Some changes take effect when ready; others begin January 1.

Do I have to enroll in all parts of Medicare at once?

No. You can enroll in Part A and Part B during your Initial Enrollment Period and wait to enroll in Part D later, as long as you do so within a certain timeframe after Part B begins. However, waiting longer than 63 days after Part B starts to enroll in Part D will result in a permanent late enrollment penalty on your Part D premium.

What if I do not have a Social Security number?

You can still enroll in Medicare if you are a lawful permanent resident or have another may have access to immigration status. You will need to provide proof of your legal residency and identity documents. Call 1-800-MEDICARE to discuss your specific situation, as the enrollment process may differ.

How much will Medicare cost me?

Part A has no monthly premium for most people but has a hospital deductible. Part B has a monthly premium set by Medicare each year (amounts vary based on income). Part D premiums vary by plan. Medicare Advantage plans vary widely — some have zero premium, others charge monthly. Your actual costs depend on which parts you choose and your income level.