Medicare starts the month you turn 65, but only if you sign up on time
Your Medicare coverage begins on the first day of the month in which you turn 65. If your birthday is January 15th, your coverage starts January 1st. If your birthday is January 1st, your coverage also starts January 1st. The exact day of your birthday within that month does not matter — what matters is that you are 65 at any point during that month.
The catch is timing. You have a seven-month window to sign up without penalty: three months before the month you turn 65, the month you turn 65 itself, and three months after. If you miss this window, your premiums go up permanently, and the increase stays with you for life. This is called a late enrollment penalty.
There is one major exception: if you or your spouse are still working and covered by an employer health plan, you can delay Medicare without penalty. You will need to tell Social Security this when you eventually sign up, and you must sign up within eight months of losing that coverage.
Key Takeaways
- Medicare coverage begins the first day of the month you turn 65, regardless of the specific date within that month.
- You have seven months total to sign up (three months before, the month of, and three months after turning 65) without facing a permanent premium increase.
- If you are still working and have employer health insurance, you can delay Medicare without penalty as long as you sign up within eight months of losing that coverage.
- You sign up through Social Security, either online at ssa.gov, by phone at 1-800-772-1213, or in person at your local Social Security office.
- Part A (hospital insurance) is usually free if you or your spouse paid Medicare taxes while working, but Part B (medical insurance) has a monthly premium that increases if you delay.
How to sign up before your coverage date
You do not have to wait until you turn 65 to sign up. In fact, signing up early is the safest approach. You can sign up starting three months before the month you turn 65.
Go to ssa.gov/benefits/retirement/index.html and select "explore for Medicare" or call Social Security at 1-800-772-1213. You can also visit your local Social Security office in person. Have your Social Security number, birth certificate, and proof of citizenship or legal residency ready. If you were born outside the United States, bring your passport or naturalization papers.
The online process takes about 15 minutes. If you explore by phone or in person, the process is similar. Social Security will ask whether you want Part A, Part B, or both. Part A covers hospital stays; Part B covers doctor visits and outpatient care. Most people take both, but you can choose Part A alone if you have other coverage for doctor visits.
What happens if you miss the sign-up window
If you do not sign up during your seven-month window, your Part B premium increases by 10 percent for each full 12-month period you were supposed to be enrolled but were not. That increase is permanent — it does not go away when you finally sign up.
For example, if you turn 65 in January 2024 and do not sign up until January 2026 (two years late), your Part B premium will be 20 percent higher than it would have been. You will pay that extra amount every month for the rest of your life.
Part A does not have the same penalty if you have worked long enough to may have access to for it free. However, if you have to pay for Part A (because you did not work long enough), a late enrollment penalty applies to Part A as well.
When coverage actually starts if you sign up late
If you sign up after your initial seven-month window closes, your coverage does not start when ready. Coverage begins the first day of the month after you sign up, or the first day of the month after Social Security processes your process, whichever is later.
This means if you sign up on March 15th, your coverage typically starts April 1st. If Social Security takes longer to process your process, it might start May 1st. There is no way to backdate Medicare coverage to cover a gap, so any medical bills you incur between turning 65 and when your coverage starts are your responsibility.
Special situations that change your start date
If you are still working and have employer health insurance, your Medicare start date can be different. You do not have to sign up when you turn 65. Instead, you can sign up within eight months after your employment ends or your employer coverage ends, whichever comes first. Your coverage will then start the first day of the month after you sign up.
If you are on Social Security disability (SSDI) or have end-stage renal disease (ESRD), you may already be on Medicare before you turn 65. In that case, your coverage continues without interruption — there is no new start date to worry about.
If you are a federal employee or railroad retiree, your Medicare start date may depend on your specific retirement plan. Contact your agency's benefits office or the Railroad Retirement Board to confirm when your coverage begins.
What to expect in the mail before your start date
About two weeks before your Medicare coverage starts, Social Security will mail you a Medicare card. This card shows your Medicare number, which is different from your Social Security number. Keep this card in a safe place — you will need it every time you see a doctor or go to a hospital.
You will also receive a document called Medicare & You, which is an annual handbook explaining your coverage options. Read the section on your coverage start date to confirm everything is correct. If your card does not arrive by the time your coverage starts, you can still see doctors and hospitals — they can look up your coverage using your Social Security number.
If you signed up for Part B, you will also receive information about your premium amount and how to pay it. Part B premiums are usually deducted from your Social Security check automatically, but you can choose to pay by mail or online instead.
Coordinating Medicare with other insurance
If you have retiree health insurance from a former employer, that coverage does not automatically end when Medicare starts. You need to contact your former employer's benefits office to understand how the two plans work together. In most cases, Medicare becomes your primary payer, and your retiree plan covers what Medicare does not.
If you have a Medigap policy (supplemental insurance), you can keep it when Medicare starts. Some Medigap policies have waiting periods or exclusions if you buy them after your Medicare start date, so it is worth shopping before you turn 65.
If you have a Medicare Advantage plan (Part C), your coverage starts on the same date as your Part A and Part B coverage. You do not need to do anything extra — the plan automatically begins when your Medicare coverage begins.
Frequently Asked Questions
What if I turn 65 on the first day of the month?
Your Medicare coverage still starts on the first day of that month. There is no difference between turning 65 on January 1st and turning 65 on January 31st — both start coverage January 1st.
Can I delay Medicare if I am still working?
Yes. If you or your spouse have employer health insurance through your job, you can delay Medicare without penalty. You must sign up within eight months of losing that coverage. When you do sign up, your coverage starts the first day of the month after Social Security processes your process.
What if Social Security loses my process?
Keep a record of when you applied and how (online, phone, or in person). If you applied online, you can log into your Social Security account to check the status. If you applied by phone or in person, call 1-800-772-1213 to confirm your process was received. If it was lost, you can reapply when ready.
Do I have to take Part B when I turn 65?
No. You can take Part A alone if you have other health insurance covering doctor visits. However, if you delay Part B and later lose that other coverage, you will face a permanent premium increase unless you sign up within eight months of losing it.
What if I am not a U.S. citizen?
You can enroll in Medicare if you are a lawful permanent resident (green card holder) or have a valid visa. You will need to provide proof of legal residency when you sign up. Contact Social Security at 1-800-772-1213 to discuss your specific situation.