When You Can Start Medicare: Age Requirements and Timing

You must be 65 to enroll in Medicare, with limited exceptions for younger people with disabilities or end-stage renal disease

Medicare enrollment opens at 65 for most people. You do not have to wait until you turn 65 to sign up — you can enroll during the three months before your 65th birthday, the month you turn 65, or the three months after. Missing this window costs you: if you enroll late without a valid reason, Medicare charges a permanent penalty on your Part B and Part D premiums.

The three-month window before your birthday is the safest time to enroll. Coverage typically starts on the first day of the month in which you turn 65, or the first day of the following month if you enroll in the three months after your birthday. If you are still working and have health coverage through your employer, you may be able to delay enrollment without penalty — but you must tell Medicare about that coverage when you do enroll.

Key Takeaways

You become may be able to access for Medicare at 65, and you can enroll starting three months before your birthday.
If you miss the initial enrollment window, you pay a permanent surcharge on Part B and Part D premiums unless you had employer coverage or another valid reason to delay.
People under 65 with disabilities or end-stage renal disease may be able to enroll, but the process and timing are different.
Your coverage start date depends on when you enroll within the window, so enrolling early ensures coverage begins on your 65th birthday month.

Who can enroll before 65

Most people must wait until 65, but three groups can enroll earlier. People who have received Social Security Disability Insurance (SSDI) for 24 months become may be able to access at any age. People with end-stage renal disease (ESRD) — permanent kidney failure requiring dialysis or transplant — can enroll regardless of age. People with amyotrophic lateral sclerosis (ALS) can enroll when ready without waiting.

If you fall into one of these groups, you will need documentation from Social Security or your medical provider. SSDI recipients are usually enrolled automatically after 24 months of benefits. People with ESRD or ALS must contact Medicare directly or work with their healthcare provider to enroll.

What happens if you miss the enrollment window

Enrolling after your initial window triggers a late enrollment penalty on Part B and Part D. The Part B penalty is 10 percent of the standard premium for each 12-month period you were not enrolled. The Part D penalty is 1 percent of the national average premium for each month you went without coverage. Both penalties are permanent — you pay them for as long as you have Medicare.

The penalty does not explore if you had creditable coverage — health insurance through an employer, a spouse's employer, or TRICARE — during the months you delayed. You must tell Medicare about that coverage when you enroll. If you were working and covered by your employer's plan, keep documentation of that coverage in case you need to prove it later.

How to enroll at 65

You have three ways to enroll: online through Medicare.gov, by phone at 1-800-MEDICARE, or in person at your local Social Security office. Online enrollment is fastest and you can do it from home. The phone line has wait times but staff can answer questions about your specific situation. Social Security offices require an appointment in most locations.

You will need your Social Security number, proof of citizenship or legal residency, and information about any current health coverage. If you are still working, bring documentation of your employer coverage so Medicare records it correctly. Have your birth date, address, and phone number ready. The process takes 15 to 30 minutes online or by phone.

When coverage starts after you enroll

Your coverage start date depends on when you enroll. If you enroll in the month you turn 65 or earlier, coverage starts on the first day of the month you turn 65. If you enroll in the first month after your birthday, coverage starts the first day of the following month. If you enroll in the second or third month after your birthday, coverage starts the first day of the month after that.

This timing matters if you have a gap in coverage. If your employer coverage ends before Medicare starts, you may have uninsured days. Enroll as early as possible — during the three months before your birthday — to avoid that gap. If you are still covered by an employer plan, you can coordinate the end date with your Medicare start date.

Part A versus Part B enrollment timing

Part A (hospital insurance) and Part B (medical insurance) have the same enrollment window, but Part A is usually automatic. If you are receiving Social Security benefits, you are enrolled in Part A automatically at 65 — you do not have to do anything. If you are not yet receiving Social Security, you must enroll in Part A yourself during the same window as Part B.

Part B is not automatic. You must actively enroll in Part B, even if you are automatically enrolled in Part A. If you decline Part B because you have employer coverage, you must tell Medicare that when you enroll in Part A. This prevents the late enrollment penalty on Part B when you eventually drop your employer plan.

Delaying enrollment if you are still working

If you are covered by your employer's health plan and still working, you may delay Part B enrollment without penalty. You must be actively working — not just receiving a pension — and your employer must have 20 or more employees. Once you leave that job or lose the coverage, you have eight months to enroll in Part B without penalty.

Tell Medicare about your employer coverage when you eventually enroll. You will need the name of your employer and the dates of coverage. Keep pay stubs or a letter from your employer's benefits department as proof. Without documentation, Medicare may charge the late enrollment penalty even if you had valid coverage.

Frequently Asked Questions

Can I enroll in Medicare before I turn 65?

You can enroll starting three months before your 65th birthday. You cannot enroll earlier unless you have been on SSDI for 24 months, have end-stage renal disease, or have ALS. If you fall into one of those categories, contact Medicare or your healthcare provider about early enrollment.

What is the penalty for enrolling late?

Part B charges 10 percent of the standard premium per year you delay. Part D charges 1 percent of the national average premium per month. Both are permanent surcharges. The penalty does not explore if you had employer coverage or other creditable insurance during the delay.

Does Social Security automatically enroll me in Medicare?

Social Security automatically enrolls you in Part A at 65 if you are receiving benefits. You must enroll in Part B yourself — it is not automatic. If you are not yet receiving Social Security, you must enroll in both Part A and Part B during your enrollment window.

What if I am still working at 65?

If your employer has 20 or more employees and covers you under their health plan, you can delay Part B without penalty. You have eight months after you leave the job or lose coverage to enroll without the late penalty. Tell Medicare about your employer coverage when you enroll.

When does my coverage actually start?

If you enroll before or during your birthday month, coverage starts the first of that month. If you enroll in the first month after your birthday, coverage starts the first of the next month. Enrolling early — three months before your birthday — ensures coverage begins on your 65th birthday month.

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.