When You Can Start Medicare: Age Requirements and Enrollment Windows

You can enroll in Medicare starting three months before you turn 65

Medicare enrollment opens on the first day of the month you turn 65, or three months before that date, whichever comes first. You do not have to wait until your 65th birthday to sign up — in fact, starting early is usually the right move because your coverage can begin on the first day of the month you turn 65, even if you enroll earlier.

The enrollment window lasts seven months total: three months before the month you turn 65, the month you turn 65, and three months after. If you miss this window, you may face a permanent penalty on your premiums, so the timing matters.

There are narrow exceptions for people still working with employer coverage, people receiving Social Security Disability Insurance (SSDI), and people with End-Stage Renal Disease (ESRD). These groups have different rules and longer enrollment periods, but the standard rule is the seven-month window around age 65.

Key Takeaways

You can enroll in Medicare three months before you turn 65, and your coverage will start on the first day of the month you turn 65.
The full enrollment window is seven months: three months before, the month of, and three months after your 65th birthday.
Missing your enrollment window can result in a permanent increase to your Part B and Part D premiums.
If you are still working with employer health insurance at 65, you may have a different enrollment timeline and should contact your employer's benefits office.
You can enroll online at Medicare.gov, by phone at 1-800-MEDICARE, or in person at your local Social Security office.

How the seven-month enrollment window works

Your Initial Enrollment Period (IEP) is the official name for this seven-month window. It runs from the first day of the month three months before you turn 65 through the last day of the month three months after you turn 65.

If you turn 65 on March 15, your window opens December 1 and closes June 30. You can enroll any day during that span. Your coverage will begin on March 1 — the first day of the month you turn 65 — regardless of when in the window you actually sign up, as long as you enroll by March 31. If you enroll in April, May, or June, your coverage starts the first day of whichever month you enroll.

This matters because gaps in coverage can be expensive. If you turn 65 on March 15 and do not enroll until July, you will have no Medicare coverage for April, May, and June. You will also owe a penalty on your Part B premium for the rest of your life.

What happens if you miss the enrollment window

If you do not enroll during your seven-month window, you enter what Medicare calls General Enrollment Period (GEP), which runs January 1 through March 31 each year. You can enroll then, but your coverage will not start until July 1 of that year — a gap of several months.

More important: you will pay a Part B late enrollment penalty of 10 percent of the standard Part B premium for each full year you were may be able to access but not enrolled. This penalty is permanent — you pay it for the rest of your life, even after you finally sign up. The same applies to Part D (prescription drug coverage): you pay a penalty of about 1 percent of the national average Part D premium for each month you were late, also permanent.

The only way to avoid these penalties is to have had creditable coverage — health insurance through an employer, a spouse's employer, TRICARE, the VA, or certain other sources — during the months you were not on Medicare. If you had creditable coverage, you can enroll without penalty during an eight-month period after that coverage ends.

Special enrollment rules for people still working

If you are still working at 65 and your employer has 20 or more employees, you may not need to enroll in Medicare Part A and Part B right away. Your employer's health plan is considered creditable coverage, and you can delay enrollment without penalty.

When you do leave that job or lose the employer coverage, you have an eight-month window to enroll in Medicare without penalty. This is called the Special Enrollment Period (SEP) for people with employer coverage. You must enroll within eight months of losing the coverage or retiring, whichever comes first.

Even if you delay Part A and Part B, you should still enroll in Part D (prescription drug coverage) during your Initial Enrollment Period if you want to avoid the permanent late-enrollment penalty. Part D penalties explore even if you have employer coverage that includes prescription drugs.

Enrolling before you turn 65: where to start

You can enroll online at Medicare.gov starting three months before your 65th birthday. You will need your Social Security number, date of birth, and citizenship or immigration status. The online process takes about 10 minutes and you get confirmation when ready.

You can also call 1-800-MEDICARE (1-800-633-4227) to enroll by phone. Representatives are available Monday through Friday, 8 a.m. to 8 p.m. Eastern time. Have your Social Security card and any current health insurance information handy.

A third option is to visit your local Social Security office in person. You can find the nearest office at ssa.gov or by calling 1-800-772-1213. Bring your Social Security card, proof of citizenship or legal residency, and proof of age (birth certificate or passport).

What you need to know about Part A and Part B

Part A covers hospital stays, skilled nursing facility care, hospice, and home health services. Most people do not pay a premium for Part A if they or their spouse paid Medicare taxes while working. You should enroll in Part A during your Initial Enrollment Period even if you are still working, because there is no penalty for delaying it and no premium to pay.

Part B covers doctor visits, outpatient care, and preventive services. Part B has a monthly premium (the standard amount in 2024 is $164.90, but it varies by income). If you delay Part B and do not have creditable employer coverage, you will pay the 10 percent late-enrollment penalty permanently. If you are still working with employer coverage, you can delay Part B without penalty.

When you turn 65, you are automatically enrolled in Part A if you are receiving Social Security benefits. You are not automatically enrolled in Part B, so you must enroll yourself or you will lose the chance to do so without penalty.

Special cases: SSDI, ESRD, and other exceptions

If you receive Social Security Disability Insurance (SSDI), you become may be able to access for Medicare automatically after you have been on SSDI for 24 months. You do not have to wait until 65. Medicare will contact you about three months before your 24-month mark, and you will be enrolled automatically in Part A and Part B unless you decline.

If you have End-Stage Renal Disease (ESRD) — permanent kidney failure requiring dialysis or transplant — you are may be able to access for Medicare regardless of age. Your enrollment window is different: it starts the month you are diagnosed or the month you begin dialysis, whichever is earlier, and lasts 12 months. You should enroll as soon as you are diagnosed because coverage can begin as early as the first day of the month you become may be able to access.

If you are a federal employee, you have different rules. Contact your agency's benefits office or the Office of Personnel Management (OPM) for guidance on when to enroll.

Frequently Asked Questions

Can I enroll in Medicare before I turn 65?

Yes. You can enroll starting three months before your 65th birthday. Your coverage will begin on the first day of the month you turn 65 if you enroll by the last day of that month. If you enroll after that, coverage starts the first day of the month you enroll.

What if I am still working at 65 and have health insurance through my job?

You can delay enrolling in Part A and Part B without penalty as long as your employer has 20 or more employees and you are actively working. When you leave the job or lose the coverage, you have eight months to enroll without penalty. You should still enroll in Part D during your Initial Enrollment Period to avoid the prescription drug penalty.

How much does it cost to enroll in Medicare?

There is no cost to enroll. Part A has no premium for most people. Part B has a monthly premium (the standard amount in 2024 is $164.90, but it varies based on income). Part D premiums vary by plan and insurance company.

What happens if I turn 65 and do not enroll?

You can still enroll during General Enrollment Period (January 1 through March 31 each year), but your coverage will not start until July 1. You will also pay a permanent 10 percent penalty on Part B premiums and a permanent penalty on Part D premiums for each month you were late.

Do I have to enroll in all parts of Medicare at the same time?

No. You can enroll in Part A and Part B separately, and you can choose whether to enroll in Part D. However, delaying Part D beyond your Initial Enrollment Period will result in a permanent penalty. If you have creditable prescription drug coverage through an employer or other source, you may be able to delay Part D without penalty.

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.