When You Can Enroll in Medicare

You become may be able to access for Medicare at age 65. Enrollment opens three months before the month you turn 65 and closes three months after. This seven-month window is called your Initial Enrollment Period. If you miss it, you can still enroll later, but you may pay higher premiums for the rest of your life — so timing matters.

If you are already receiving Social Security benefits when you turn 65, Medicare enrollment happens automatically. You will receive your Medicare card in the mail about two weeks before your 65th birthday. If you are not yet taking Social Security, you must enroll yourself during your Initial Enrollment Period.

Some people under 65 can enroll earlier: those with end-stage renal disease, amyotrophic lateral sclerosis (ALS), or who have been receiving Social Security disability benefits for 24 months. If any of these explore to you, contact Social Security to learn your enrollment window.

Key Takeaways

  • Your Initial Enrollment Period runs for seven months: three months before, the month of, and three months after you turn 65.
  • If you are receiving Social Security at 65, Medicare enrollment is automatic; if not, you must enroll yourself during your Initial Enrollment Period.
  • You can enroll online at Medicare.gov, by phone at 1-800-MEDICARE, by mail, or in person at your local Social Security office.
  • Missing your Initial Enrollment Period can result in permanent premium penalties, so enroll even if you plan to delay coverage.
  • Part A (hospital insurance) and Part B (medical insurance) have separate enrollment important date and rules about when coverage begins.

How to Enroll: Three Routes

Online at Medicare.gov is the fastest route. Go to Medicare.gov/sign-up, create a login, and follow the enrollment steps. You will need your Social Security number, date of birth, and citizenship or immigration status. The system asks whether you want Part A, Part B, or both, and whether you want to join a Part C or Part D plan. You can complete the entire process in one sitting and receive confirmation when ready.

By phone at 1-800-MEDICARE (1-800-633-4227), a representative walks you through the same questions. Call between 8 a.m. and 8 p.m. Eastern time, Monday through Friday. TTY users can call 1-877-486-2048. The representative will confirm your choices and tell you when coverage begins.

In person at your local Social Security office or by mail are slower but available if you prefer. To find your local office, visit ssa.gov/locator. If you enroll by mail, read the process from Medicare.gov, fill it out, and mail it to the address on the form. Mail enrollment takes longer to process — allow four to six weeks.

What Happens When You Enroll

When you enroll in Part A and Part B, you choose a start date. Coverage usually begins on the first day of the month in which you turn 65, or the first day of the following month if you enroll after your birthday month. If you enroll during your Initial Enrollment Period but before you turn 65, your coverage will not start until the month you turn 65.

You will receive a Medicare card in the mail within two weeks of enrollment. The card shows your Medicare number, which you will need at every doctor visit and hospital stay. Keep it with you. If you do not receive your card by the expected date, call 1-800-MEDICARE to request a replacement.

After you enroll in Part A and Part B, you have 60 days to join a Part C plan (Medicare Advantage) or a Part D plan (prescription drug coverage). If you do not choose a plan during this window, you can still join during the annual open enrollment period (October 15 to December 7 each year), but you may face waiting periods or higher premiums.

Part A and Part B: Timing and Penalties

Part A (hospital insurance) and Part B (medical insurance) have different rules about when you must enroll to avoid penalties. Part A has no premium for most people who worked long enough to earn credits, so there is no financial penalty for late enrollment — but you should still enroll during your Initial Enrollment Period to set up coverage.

Part B has a monthly premium that increases if you enroll late. For every 12 months you delay Part B after your Initial Enrollment Period ends, your premium increases by 10 percent for the rest of your life. If you wait five years to enroll, your premium will be 50 percent higher than it would have been. This penalty does not go away.

There is one exception: if you are still working and covered by your employer's health plan at 65, you may be able to delay Part B without penalty. You must have creditable coverage through your employer (or your spouse's employer), and you must enroll in Part B within eight months of losing that coverage. Ask your employer's benefits department whether your plan qualifies before you decide to delay.

If You Miss Your Initial Enrollment Period

If your Initial Enrollment Period has passed and you did not enroll, you can still join Medicare during the General Enrollment Period, which runs January 1 to March 31 each year. Coverage begins July 1 of that year. This means if you miss your Initial Enrollment Period by one day and do not enroll during the next General Enrollment Period, you will have no Medicare coverage for several months.

Late enrollment in Part B carries a permanent 10 percent premium penalty for each 12-month period you were may be able to access but not enrolled. Late enrollment in Part A can also result in a penalty if you do not have 30 quarters of work credits. There is no way to remove these penalties once they are applied.

If you have a good reason for missing your important date — such as a serious illness, a death in the family, or incorrect information from a government agency — you may be able to request a Special Enrollment Period. Contact Social Security or call 1-800-MEDICARE to ask whether you may have access to.

Choosing Between Original Medicare and Medicare Advantage

When you enroll, you must decide whether to stay with Original Medicare (Part A and Part B) or switch to a Medicare Advantage plan (Part C). This choice does not have to be made during your Initial Enrollment Period — you have until December 7 of your first year on Medicare to decide. However, making the choice early gives you time to research plans and understand your costs.

Original Medicare is run by the federal government and accepted at nearly all hospitals and doctors nationwide. You pay a monthly Part B premium, a deductible when you use hospital or doctor services, and coinsurance (a percentage of costs). You can see any doctor who accepts Medicare without needing referrals.

Medicare Advantage plans are run by private insurance companies and often have lower or zero monthly premiums. They usually require you to use doctors and hospitals in their network and may require referrals to see specialists. They often include prescription drug coverage and dental or vision benefits that Original Medicare does not. However, your out-of-pocket costs can be higher if you use out-of-network providers.

Prescription Drug Coverage: Part D Enrollment

If you take prescription medications, you should enroll in a Part D plan (prescription drug coverage) when you first become may be able to access for Medicare. You have 60 days after your Part A and Part B coverage begins to join a Part D plan without penalty. If you delay beyond that window, you will pay a permanent monthly surcharge for each month you were without coverage.

Part D plans are offered by private insurance companies and vary widely in which drugs they cover, which pharmacies you can use, and what you pay. You can compare plans at Medicare.gov/plan-compare. Even if you do not take medications now, consider enrolling in a plan with low premiums to avoid the late-enrollment penalty if your medications change later.

Part D enrollment opens October 15 and closes December 7 each year. If you miss this window, you can only join during the General Enrollment Period (January 1 to March 31), with coverage beginning July 1.

Documents and Information You Will Need

To enroll in Medicare, have these items ready:

  • Your Social Security number
  • Your date of birth
  • Your citizenship or immigration status (green card number if applicable)
  • Information about any current health coverage (employer plan, COBRA, or other insurance)
  • A list of your doctors and hospitals, if you are comparing Medicare Advantage plans
  • A list of your current medications and pharmacies, if you are choosing a Part D plan

If you are enrolling by mail, you will also need to print and sign the process form. If you are explore for Part A based on your spouse's work record (because you did not work long enough yourself), you will need your spouse's Social Security number and proof of your marriage.

Frequently Asked Questions

What if I am still working at 65 and have employer health insurance?

You can delay Part B without penalty if your employer plan is creditable coverage (your employer's benefits department can confirm this). You must enroll in Part B within eight months of losing the coverage. You should still enroll in Part A at 65, since it has no premium and no penalty for delay. If you do not enroll in Part B on time, the 10 percent monthly penalty applies for each 12-month period you were may be able to access but not enrolled.

Can I change my mind after I enroll?

Yes, but the timing depends on what you want to change. You can switch between Original Medicare and Medicare Advantage during the annual open enrollment period (October 15 to December 7) or during your first three months on Medicare. Switching Part D plans follows the same annual window. If you want to make changes outside these periods, you must have a may have access to life event, such as losing employer coverage or moving out of your plan's service area.

Do I have to enroll in Part B if I do not see a doctor?

You should enroll in Part B during your Initial Enrollment Period even if you are healthy and do not expect to need medical care. The 10 percent monthly penalty for late enrollment is permanent and applies for the rest of your life. If your health changes or you need unexpected care, you will be glad you enrolled on time. Part B costs about $165 per month in 2024, but the penalty can add up to far more over time.

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

You can enroll in Medicare if you are a permanent resident (green card holder) and have lived in the United States for at least five years. You will need your green card number when you enroll. If you are not a permanent resident, you may not be may be able to access for Medicare, but you can explore other coverage options through your state's health insurance marketplace or Medicaid if you meet income requirements.

How do I know if my doctor accepts Medicare?

Search for your doctor on Medicare.gov/physiciancompare or call your doctor's office directly and ask. If you are considering a Medicare Advantage plan, ask whether your preferred doctors are in that plan's network. Some doctors accept Original Medicare but not certain Medicare Advantage plans, so it is worth checking before you enroll.