When To Start Your Medicare Enrollment Before You Turn 65

Sign up three months before your 65th birthday month

You should begin your Medicare enrollment during the three-month window that starts three months before the month you turn 65. For example, if your birthday is in June, you would start the process in March. This timing matters because Medicare coverage typically begins on the first day of your birthday month, but only if you enroll during this window.

The enrollment window itself lasts seven months total: three months before your birthday month, your birthday month itself, and three months after. However, waiting until after your birthday month can delay your coverage start date. If you miss this window entirely, you may face a permanent penalty on your premiums, even if you sign up years later.

You can enroll online through Medicare.gov, by phone at 1-800-MEDICARE, or in person at your local Social Security office. The process takes about 10 minutes online if you have your Social Security number and information about your current health coverage.

Key Takeaways

Start your enrollment three months before your 65th birthday month to may support coverage begins on the first day of that month.
You have a seven-month enrollment window total, but waiting past your birthday month delays when your coverage actually starts.
Missing the initial enrollment window can result in a permanent late-enrollment penalty added to your Part B and Part D premiums for life.
You can enroll online at Medicare.gov, by phone, or at a Social Security office without paying any fee to enroll.
If you are still working and have employer coverage, you may have different rules and should contact your employer's benefits office before enrolling.

Why the three-month window matters

Medicare processes enrollments in batches, and the three-month advance window gives the system time to verify your information, coordinate with Social Security, and prepare your coverage documents. If you enroll during this window, your coverage begins automatically on the first day of your birthday month. This means no gap in health insurance and no period where you are uninsured.

If you enroll after your birthday month, your coverage will not start until the first day of the month after you enroll. For someone who enrolls in August after a June birthday, coverage would not begin until September. That creates a gap of at least two months where you have no Medicare coverage and are responsible for any medical costs yourself.

What happens if you miss the important date

Missing your initial enrollment window triggers a late-enrollment penalty that stays with you permanently. For Part B, the penalty is 10 percent of the standard premium for each full year you were may be able to access but not enrolled. For Part D (prescription drug coverage), the penalty is 1 percent of the national average premium for each month you were not enrolled. These penalties are added to your monthly bill for as long as you have Medicare.

The only exceptions to this penalty are if you had other creditable health coverage (such as employer insurance or TRICARE) during the time you were not enrolled in Medicare. If you had continuous coverage through an employer or union, you generally will not owe a penalty when you do enroll. You will need to provide proof of that coverage when you sign up.

Special rules if you are still working

If you are still employed and your employer has a health plan with 20 or more employees, you may not need to enroll in Medicare Part B right away. You can delay Part B enrollment without penalty as long as you remain covered under your employer's plan and are actively working. However, you should still enroll in Part A (hospital insurance) at 65, even if you delay Part B.

Contact your employer's benefits office or human resources department before your 65th birthday to understand your options. They can tell you whether your plan is considered creditable coverage and what happens to your employer coverage when you do enroll in Medicare. Some employers automatically drop you from their plan once you turn 65, while others let you stay enrolled.

If your employer coverage ends before you enroll in Medicare Part B, you will have eight months from the date coverage ends to enroll without penalty. This is called a special enrollment period. You will need to provide proof that your employer coverage ended.

How to enroll and what to have ready

You can start the enrollment process online at Medicare.gov without leaving home. You will need your Social Security number, date of birth, and information about any current health insurance you have. The online process typically takes 10 to 15 minutes. You can also call 1-800-MEDICARE to enroll by phone with a representative, or visit your local Social Security office in person.

If you enroll online, you will receive a confirmation number when ready. Medicare will mail you your official enrollment documents and your Medicare card within two weeks. Do not wait for the card to arrive before seeking care; your coverage begins on the date Medicare confirms, and providers can look up your enrollment status.

If you have questions about your specific situation, Social Security representatives can answer them during the enrollment call. They can also tell you whether you may have access to for any programs that help pay your premiums or out-of-pocket costs.

Coordinating with other insurance you have

If you have retiree health coverage from a former employer, union, or COBRA continuation coverage, you should contact that plan before enrolling in Medicare. Some retiree plans coordinate with Medicare, meaning Medicare becomes primary and the retiree plan covers some of what Medicare does not. Other plans end when you turn 65. Understanding how your current coverage works prevents gaps and unexpected bills.

If you have Medicaid (state health insurance for low-income people), your state Medicaid office should be notified when you enroll in Medicare. Medicaid and Medicare work together, and Medicaid may help pay your Medicare premiums and cost-sharing. You do not need to unenroll from Medicaid when you sign up for Medicare.

What to do if you turned 65 and did not enroll

If you are past your initial enrollment window and did not sign up, you can still enroll during the General Enrollment Period, which runs from January 1 to March 31 each year. Coverage would begin July 1 of that year. However, you will owe the late-enrollment penalty unless you had creditable coverage during the time you were not enrolled.

If you had a major life event—such as loss of employer coverage, loss of Medicaid, or moving to a new state—you may may have access to for a Special Enrollment Period that allows you to enroll outside the normal windows without penalty. Contact Medicare at 1-800-MEDICARE to find out whether your situation qualifies.

Frequently Asked Questions

What if my birthday is in January—when do I start enrolling?

You would start enrolling in October of the previous year. Your three-month window opens three months before your birthday month, so for a January birthday, that window opens in October. Your coverage would begin January 1 if you enroll during October, November, December, or January.

Do I have to enroll in Part A and Part B at the same time?

You can enroll in Part A and Part B separately, but both should be done during your initial enrollment window to avoid penalties. Part A (hospital insurance) rarely has a penalty, but Part B (medical insurance) does. If you are still working with employer coverage, you may delay Part B but should still enroll in Part A at 65.

Can I change my mind after I enroll?

Yes. You have until March 31 of the year after you first enroll to make changes to your coverage choices. After that, you can make changes only during the annual Open Enrollment Period from October 15 to December 7 each year, or if you have a may have access to life event.

What if I do not know my exact birthday or Social Security number?

Call 1-800-MEDICARE or visit your local Social Security office. A representative can help you locate your information or verify it before you enroll. You can also create an account on Medicare.gov and update your information there.

Is there a fee to enroll in Medicare?

No. Enrolling in Medicare itself is free. You will pay premiums for Part B and Part D coverage, and possibly Part A if you do not have enough work credits, but the enrollment process itself has no cost.

This guide is for general information only and is not medical, financial, legal, or other professional advice. For decisions specific to your situation, consult a qualified professional. See our Editorial Policy.