Enroll in Medicare during your Initial Enrollment Period, which starts three months before the month you turn 65 and runs for seven months total

Your Initial Enrollment Period is a one-time window that opens automatically. It begins on the first day of the three months before your 65th birthday month and closes on the last day of the three months after. If you turn 65 in June, your window opens February 1 and closes August 31. You do not have to wait until your birthday to sign up — you can enroll as soon as the window opens.

Missing this window costs you money. If you do not enroll when you are first may be able to access and you do not have other coverage that counts as "creditable" (employer coverage, union coverage, or certain military plans), Medicare charges you a late enrollment penalty. This penalty is permanent — it stays on your bill for as long as you have Medicare Part B or Part D. The penalty grows the longer you wait, calculated as a percentage of the standard premium for each month you were not enrolled.

The only exception is if you have group health insurance through an employer or union where you or your spouse still works. In that case, you can delay enrollment without penalty, but you must enroll within eight months of losing that coverage or retiring, whichever comes first.

Key Takeaways

  • Your Initial Enrollment Period is seven months long and starts three months before you turn 65, so you can enroll before your birthday without waiting.
  • Enrolling late triggers a permanent penalty on your Medicare Part B and Part D premiums if you do not have other may have access to coverage.
  • If you have employer or union coverage, you can delay enrollment without penalty as long as you sign up within eight months of losing that coverage.
  • You can enroll online through Medicare.gov, by phone at 1-800-MEDICARE, or in person at your local Social Security office.
  • Part A (hospital insurance) is usually automatic if you receive Social Security, but you must actively enroll in Part B (medical insurance) and Part D (prescription drug coverage).

What counts as creditable coverage that lets you delay

If you have health insurance through your job or your spouse's job, you can wait to enroll in Medicare without facing a late penalty. The same protection applies if you have coverage through a union, COBRA continuation coverage, or certain military or veterans plans. The key is that your coverage must be "creditable" — meaning it covers at least as much as Medicare Part B would.

When you lose this coverage, you enter a new eight-month window to enroll in Medicare without penalty. This clock starts the month your coverage ends, not the month you realize it ended. If your employer coverage stops in March, you have until November to enroll. If you miss that important date, the late penalty applies to Part B and Part D for the rest of your life.

Losing a job, retiring, or your employer dropping coverage all trigger this eight-month window. Divorce does not — if you were covered under a spouse's plan and you divorce, you lose creditable coverage when ready and should enroll in Medicare right away.

How to enroll during your Initial Enrollment Period

You have three ways to enroll: online at Medicare.gov, by phone at 1-800-MEDICARE (1-800-633-4227), or in person at your local Social Security office. Online enrollment is usually the fastest — you can complete it in about 10 minutes if you have your Social Security number and information about any current coverage.

By phone, a representative will walk you through the same questions and can answer questions about which parts you need. Wait times vary; calling early in the week or early in the day is usually faster. In person, you bring your Social Security card, proof of citizenship or legal residency, and information about any current health coverage, and a Social Security employee completes the enrollment on the spot.

Part A (hospital insurance) enrolls automatically for most people who receive Social Security benefits. You still need to actively enroll in Part B (medical insurance) and Part D (prescription drug coverage). If you do not receive Social Security yet, you must enroll in all three parts yourself during your Initial Enrollment Period.

Why enrolling early in your window matters

Medicare coverage does not start the day you enroll — it starts the first day of the month in which you enroll, or the first day of the following month, depending on when you sign up. If you enroll in February, coverage can start February 1. If you enroll in mid-February, coverage might not start until March 1. Enrolling early in your seven-month window gives you time to fix any errors before coverage begins.

Errors happen. Social Security might have your name spelled differently than your birth certificate, your address might be wrong, or your citizenship status might not process correctly. If you enroll in month three of your window and an error appears, you have four months to contact Medicare and fix it. If you wait until month seven and an error appears, you have no buffer — coverage starts with the error in place.

Enrolling early also means you receive your Medicare card in the mail before your coverage starts, so you have it ready for your first doctor visit. Cards usually arrive within two weeks of enrollment.

Part A, Part B, and Part D: what you must choose

Medicare has four parts. Part A covers hospital stays, skilled nursing facilities, hospice, and home health care. Part B covers doctor visits, outpatient care, and medical equipment. Part D covers prescription drugs. Part C (Medicare Advantage) is an alternative to Parts A and B offered by private insurance companies — you cannot have both Original Medicare (Parts A and B) and Part C at the same time.

Part A is usually automatic if you receive Social Security. You do not have to do anything. Part B is not automatic — you must choose to enroll. If you do not enroll in Part B during your Initial Enrollment Period and you do not have other creditable coverage, you pay a late penalty for as long as you have Medicare.

Part D (prescription drugs) is separate from Parts A and B. You choose a plan from private insurance companies that Medicare approves. If you do not enroll in Part D when you are first may be able to access and you go without creditable drug coverage, you pay a late penalty. The penalty is based on how many months you were not enrolled and the national average cost of Part D plans.

Special enrollment periods if you miss your Initial Enrollment Period

If you miss your Initial Enrollment Period, you may still have a chance to enroll without penalty through a Special Enrollment Period. These are limited windows that open for specific reasons: losing employer coverage, moving out of your plan's service area, becoming a U.S. citizen, or having Medicare make an error on your record.

The most common Special Enrollment Period is the one triggered by losing employer coverage. As mentioned earlier, you have eight months from the date your coverage ends. Other Special Enrollment Periods vary in length — some are 60 days, some are longer. You must contact Medicare directly to request a Special Enrollment Period; they do not open automatically.

If you do not may have access to for a Special Enrollment Period, you can still enroll during the General Enrollment Period, which runs January 1 through March 31 each year. Coverage would start July 1 of that year. Late penalties still explore if you enroll this way.

The cost of waiting: late enrollment penalties explained

A late enrollment penalty for Part B is 10 percent of the standard Part B premium for each full year you were not enrolled. If the standard premium is $165 per month and you wait two years to enroll, your penalty is 20 percent — an extra $33 per month added to your bill permanently. This penalty does not go away if you move, change plans, or reach a certain age.

Part D penalties work the same way: 1 percent of the national average cost of a basic prescription drug plan for each month you were not enrolled. If you go three years without Part D coverage, your penalty is 36 percent of that average cost, added to your premium every month for life.

These penalties are why enrolling during your Initial Enrollment Period or within eight months of losing creditable coverage matters. The cost of waiting compounds quickly and never disappears.

Frequently Asked Questions

Can I enroll in Medicare before I turn 65?

Yes. Your Initial Enrollment Period opens three months before the month you turn 65, so you can enroll as early as then. You do not have to wait until your birthday or until the month you turn 65. Enrolling early gives you time to receive your Medicare card and resolve any errors before coverage starts.

What happens if I am still working at 65?

If you or your spouse are still working and have employer health coverage, you can delay enrolling in Medicare Part B without penalty. You must enroll within eight months of retiring or losing that coverage. Part A (hospital insurance) does not have the same rule — you should enroll in Part A even if you delay Part B, because Part A has no monthly premium if you have worked long enough.

Do I lose my current insurance if I enroll in Medicare?

If you have employer coverage, you keep it until you lose it or retire. Medicare becomes your secondary insurance until your employer coverage ends. If you have individual market insurance (coverage you bought yourself), you should contact your insurance company to cancel it once Medicare starts, because you do not need both and paying for both wastes money.

What if I turn 65 and do not think I need Medicare?

You should still enroll in Part A during your Initial Enrollment Period, because it has no monthly premium and covers hospital stays. Delaying Part B is an option if you have employer coverage, but delaying Part A costs you nothing and protects you if you have an accident or sudden illness. Skipping enrollment entirely triggers late penalties that last for life.

Can I change my mind after I enroll?

Yes. You have a seven-month disenrollment period that runs from the month your coverage starts through seven months after. During this time, you can switch between Original Medicare and Medicare Advantage, or drop Part D and re-enroll later without penalty. After this period ends, you can only make changes during the annual open enrollment period (October 15 through December 7) or if you may have access to for a Special Enrollment Period.