Sign up for Medicare during your initial enrollment period, which starts three months before the month you turn 65

Your initial enrollment period lasts seven months total: three months before your 65th birthday month, the month you turn 65, and three months after. If you sign up during this window, your coverage begins on the first day of your birthday month. This is the only time you get this full seven-month window without penalties.

If you miss this window, you can still sign up later, but you will pay a permanent penalty on your monthly premiums for as long as you have Medicare. The penalty is 10 percent of the standard Part B premium for each full year you were may be able to access but did not sign up. For example, if you turned 65 in January 2023 and did not sign up until January 2025, you would owe a 20 percent penalty on top of your regular premium for life.

The only exception is if you had health coverage through your job or your spouse's job when you turned 65. In that case, you have an eight-month grace period after that coverage ends to sign up without penalty. You must be able to prove you had that coverage—usually through a letter from your employer or health plan.

Key Takeaways

  • Your initial enrollment period is seven months long: three months before you turn 65, your birthday month, and three months after.
  • Signing up during your initial period means coverage starts on the first of your birthday month with no late penalties.
  • If you miss your initial period and had no employer coverage, you will pay a permanent 10 percent penalty on Part B premiums for each year you delayed.
  • If you had job-based health coverage when you turned 65, you have eight months after that coverage ends to sign up penalty-free.
  • You sign up through Medicare.gov, by phone at 1-800-MEDICARE, or in person at your local Social Security office.

What happens if you are still working at 65

If you are still employed and your employer has 20 or more workers, you may not need to sign up for Medicare Part B right away. Your employer's health plan is the primary payer, meaning it pays first. You can delay Part B without penalty as long as you are actively working and covered under that plan.

However, you must still sign up for Part A (hospital insurance) when you turn 65, even if you are working. Part A is free for most people, and signing up does not affect your employer coverage. You have the same seven-month initial enrollment period for Part A.

Once you leave your job or lose that coverage, you have eight months to sign up for Part B without penalty. Do not wait longer than that, because the penalty clock starts after those eight months end. If your employer has fewer than 20 workers, different rules explore—ask your employer's benefits office or call 1-800-MEDICARE to confirm your situation.

Signing up before 65 if you receive disability or kidney disease benefits

If you receive Social Security Disability Insurance (SSDI) or are on dialysis or have end-stage renal disease, you become may be able to access for Medicare before age 65. SSDI recipients become may be able to access after 24 months of receiving benefits. People with end-stage renal disease become may be able to access when ready.

For SSDI recipients, Medicare enrollment happens automatically after your 24-month waiting period ends. You do not need to do anything—Social Security will enroll you in Parts A and B. Your coverage begins on the first day of the month you become may be able to access.

If you have end-stage renal disease, you should sign up during your initial enrollment period, which is the same seven-month window: three months before may be able to access, your may be able to access month, and three months after. If you miss this window, you will face the same late penalties as someone who delays at 65.

How to sign up and what documents you need

You can sign up for Medicare in three ways: online at Medicare.gov, by phone at 1-800-MEDICARE (1-800-633-4227), or in person at your local Social Security office. Online signup is usually fastest and you can do it from home.

Have your Social Security number and proof of citizenship or legal residency ready. If you were born outside the United States, bring your passport or immigration documents. You will also need information about any current health coverage, including employer plans, COBRA, or Medicaid. If you are signing up for Part B, you will choose whether to enroll in Original Medicare (Parts A and B) or a Medicare Advantage plan.

If you sign up online, you can complete the process in about 10 minutes. If you call, expect to spend 15 to 30 minutes on the phone, depending on how busy the line is. Social Security offices have longer wait times, especially near the end of the month, but staff can answer detailed questions about your specific situation.

What to do if you missed your initial enrollment period

If you did not sign up during your initial enrollment period and you no longer have employer coverage, 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 means if you sign up in January, you will have a six-month gap with no coverage.

During this gap, you are responsible for all medical costs. Hospital stays, doctor visits, and prescriptions are not covered. This is why signing up during your initial period is so important—you avoid both the gap in coverage and the permanent penalty.

If you have a may have access to life event—such as losing employer coverage, moving to a new state, or losing Medicaid—you may be able to sign up outside the normal enrollment periods. These situations trigger a Special Enrollment Period that lasts two months. Call 1-800-MEDICARE to report a may have access to event and ask whether you are may be able to access for a Special Enrollment Period.

Understanding Part A and Part B enrollment

Medicare has different parts, and the enrollment rules differ slightly for each. Part A covers hospital stays, skilled nursing care, hospice, and some home health services. Part B covers doctor visits, outpatient care, lab tests, and some preventive services. Most people sign up for both at the same time during their initial enrollment period.

Part A is free for most people who paid Medicare taxes while working. Part B has a monthly premium that changes each year—in 2024 it was $164.90 per month for most people, though higher earners pay more. If you delay Part B past your initial enrollment period, your premium increases by 10 percent for each year you delayed, and that increase is permanent.

If you choose a Medicare Advantage plan (Part C) instead of Original Medicare, you are automatically enrolled in Parts A and B through that plan. Medicare Advantage plans include prescription drug coverage (Part D) and often include dental, vision, and hearing benefits that Original Medicare does not cover. You choose your plan during your initial enrollment period, and you can change plans once per year during the Annual Enrollment Period (October 15 through December 7).

Frequently Asked Questions

Can I sign up for Medicare before I turn 65?

You can sign up three months before your 65th birthday. This is the earliest you can enroll during your initial period. If you receive disability benefits or have end-stage renal disease, you become may be able to access before 65 and can sign up when you become may be able to access. Otherwise, you must wait until three months before your 65th birthday month.

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

Your coverage begins on the first day of the month you turn 65, regardless of which day of the month your birthday falls on. So if you turn 65 on June 15, your coverage starts June 1. You should sign up by the end of May to may support coverage begins on time.

Do I have to sign up for Part D prescription drug coverage at 65?

You do not have to, but if you go without creditable prescription drug coverage for more than 63 days, you will pay a permanent penalty when you do sign up. The penalty is about 1 percent of the national average Part D premium for each month you were without coverage. If you do not take prescription drugs, you can skip Part D, but sign up later if your situation changes.

What happens to my employer health insurance when I sign up for Medicare?

You should contact your employer's benefits office to ask how signing up for Medicare affects your coverage. Some employers require you to drop their plan once you are on Medicare. Others let you keep both. Medicare becomes your primary payer once you are enrolled, so your employer plan pays secondary. Coordinate with your benefits office before you sign up to avoid coverage gaps.

Can I change my mind after I sign up?

Yes, but only during specific windows. If you sign up for Original Medicare and want to switch to Medicare Advantage, you can do so during the Annual Enrollment Period (October 15 through December 7) or during your initial enrollment period if you have not yet enrolled. If you sign up for Medicare Advantage and want to switch back to Original Medicare, you have the same windows, plus a one-time trial period if you are in your first year of Medicare.