Medicare starts the month you turn 65, or the first day of the month after you turn 65

Your Medicare coverage begins on the first day of the month in which you turn 65, or the first day of the following month if your birthday falls on the first of the month. If you were born on January 15, your coverage starts January 1. If you were born on January 1, your coverage starts February 1. This timing is automatic—you do not have to wait for a card or approval letter to arrive.

The start date depends on whether you have already signed up. If you enrolled before your 65th birthday, coverage begins on your may be able to access date. If you did not enroll before turning 65, your coverage will start the month you do enroll, but you may face a late-enrollment penalty that increases your premiums permanently. The penalty is 10 percent of the Part B premium for each full year you delayed, and it stays on your bill for as long as you have Medicare.

You do not have to be retired to get Medicare at 65. Your work status does not change your start date. If you are still working and covered by your employer's health plan, you can delay Part B enrollment without penalty as long as your employer has 20 or more employees and you are actively employed. You will need to enroll in Part B within eight months of leaving that job to avoid the penalty.

Key Takeaways

  • Medicare coverage begins the first day of the month you turn 65, regardless of your work status or whether you have received your card yet.
  • You must enroll before your 65th birthday or within a specific window after to avoid a permanent 10 percent penalty on Part B premiums.
  • If you are covered by an employer health plan with 20 or more employees, you can delay Part B without penalty as long as you enroll within eight months of leaving that job.
  • Part A (hospital insurance) is usually automatic if you have paid into Social Security, but you must actively enroll in Part B (medical insurance) and Part D (prescription drug coverage).
  • Your Medicare card will arrive in the mail before your coverage starts, but coverage is active even if the card has not yet arrived.

How to enroll before your start date

You should enroll in Medicare during your Initial Enrollment Period, which runs for seven months: three months before the month you turn 65, the month you turn 65, and three months after. If you miss this window, you will pay the late-enrollment penalty for the rest of your life.

You can 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 through Medicare.gov is the fastest route—you can complete it in about 15 minutes if you have your Social Security number and information about any current health coverage. By phone, expect to wait 30 to 45 minutes during business hours, especially in the months before your birthday.

When you enroll, you will choose between Original Medicare (Part A and Part B) or a Medicare Advantage plan (Part C). Original Medicare is the federal program run by the Centers for Medicare and Medicaid Services. Medicare Advantage plans are sold by private insurance companies and bundle hospital, medical, and usually prescription drug coverage into one plan. Both options start on the same date, but the plan you choose affects your out-of-pocket costs and which doctors you can see.

What happens if you miss the enrollment window

If you do not enroll during your Initial Enrollment Period and you do not have an exception (such as active employer coverage), your Part B coverage will start the first day of the month after you enroll. You will also owe a permanent 10 percent penalty on your Part B premium for each full year you were may be able to access but not enrolled.

The penalty is calculated on the standard Part B premium for the year you enroll. In 2024, the standard premium is $174.70 per month. If you delayed for two years, your penalty would be 20 percent, or about $35 per month added to your premium for life. This penalty does not go away if you switch plans or move to a different state.

You can still enroll after missing the important date, but you should do so as soon as possible. There is no important date for late enrollment—you can enroll at any time. However, the longer you wait, the longer you will pay the penalty. If you have a valid reason for missing the important date (called a "special circumstance"), you may be able to request a waiver of the penalty. Contact Medicare directly to discuss your situation.

Part A versus Part B: which starts when

Part A (hospital insurance) covers inpatient hospital stays, skilled nursing facility care, hospice, and home health services. If you have paid into Social Security for at least 10 years (40 quarters), Part A is automatic—you do not have to enroll. It starts on your may be able to access date even if you do not sign up. You will receive a Medicare card in the mail that shows your Part A coverage.

Part B (medical insurance) covers doctor visits, outpatient care, lab tests, and medical equipment. You must actively enroll in Part B. If you do not enroll during your Initial Enrollment Period and you do not have employer coverage, your coverage will start the month after you enroll, and you will owe the late-enrollment penalty. Part B has a monthly premium that changes each year—in 2024 it is $174.70 for most people, though higher earners pay more.

Part D (prescription drug coverage) must also be chosen during your Initial Enrollment Period. If you do not enroll and you do not have other drug coverage, you will owe a late-enrollment penalty of about 1 percent of the national average premium for each month you were may be able to access but not enrolled. This penalty also stays on your bill for life. Part D coverage starts the first day of the month after you enroll.

What to expect in the months before your start date

About three months before your 65th birthday, you will receive a notice from Social Security in the mail. This notice explains your Medicare options and tells you how to enroll. Read it carefully—it includes your may be able to access date and information about any employer coverage you reported to Social Security.

Your Medicare card will arrive in the mail about two weeks before your coverage starts. The card shows your Medicare number (which is now your Social Security number followed by a letter), your name, and the date your coverage begins. You do not need the card to receive care—your coverage is active on your start date even if the card has not arrived. However, you should keep the card in a safe place once it arrives, because you will need it to show providers and pharmacies.

If you are still working and covered by an employer plan, tell your employer's benefits department that you are turning 65. They will need to know whether you want to keep the employer coverage or switch to Medicare. Some employers require you to enroll in Medicare Part A at 65 even if you stay on the employer plan, so check your plan documents or ask your benefits administrator.

Starting Medicare while still working

You can start Medicare at 65 even if you are still working and earning income. Your work does not delay your start date or change your coverage. However, if you are covered by your employer's health plan, you have options about when to enroll in Part B.

If your employer has 20 or more employees and you are actively employed, you can delay Part B enrollment without penalty. Your employer coverage is considered primary, meaning it pays first, and Medicare pays second. You must enroll in Part B within eight months of leaving that job—the eight-month window starts the month after your employment ends or your coverage ends, whichever comes first. If you miss this window, you will owe the late-enrollment penalty.

If your employer has fewer than 20 employees, you must enroll in Part B when you turn 65, or you will owe the penalty. In this case, Medicare becomes primary and your employer coverage becomes secondary.

How your start date affects your first bill

Your first Part B premium is usually deducted from your first Social Security check. If you do not yet receive Social Security, Medicare will bill you directly. Your first bill will arrive in the month before your coverage starts, showing the premium for your first month of coverage.

If you enroll in a Medicare Advantage plan, you will receive a bill from the insurance company, not from Medicare. The bill will show your monthly premium (which may be zero if the plan has no premium) and any out-of-pocket costs for care you received during that month.

If you enroll in Part D, your first prescription drug premium will be billed separately. Some plans bill monthly, and some allow you to pay quarterly or annually. Check your plan documents to see how your plan bills.

Frequently Asked Questions

Does my Medicare start date change if I enroll late?

Yes. If you enroll during your Initial Enrollment Period, coverage starts on your may be able to access date (the first of the month you turn 65). If you enroll after that window, coverage starts the first day of the month after you enroll. You will also owe a permanent penalty on Part B premiums.

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

Your coverage starts on the first day of that month, not on your birthday. If you were born on January 15, your Medicare starts January 1. If you were born on January 1, your Medicare starts February 1.

Can I delay Medicare if I am still working?

You can delay Part B without penalty if you are covered by an employer health plan with 20 or more employees and you are actively employed. You must enroll within eight months of leaving that job. Part A is automatic and cannot be delayed if you are may be able to access, though you can refuse it.

Will I receive my Medicare card before coverage starts?

Your card will arrive about two weeks before your start date. Your coverage is active on your start date even if the card has not arrived. You do not need the card to receive care, but you should keep it once it arrives.

What happens to my employer coverage when Medicare starts?

You can keep both. If your employer has 20 or more employees, your employer coverage is primary and Medicare is secondary. If your employer has fewer than 20 employees, Medicare is primary. Tell your employer's benefits department that you are turning 65 so they can coordinate coverage correctly.