Start Medicare at 65, or earlier if you have a disability or end-stage renal disease

You become Medicare-may be able to access at age 65 if you are a U.S. citizen or permanent resident who has lived in the country for at least five years. If you have been receiving Social Security Disability Insurance (SSDI) for 24 months, or if you have end-stage renal disease (ESRD) or ALS, you can start Medicare before 65. Most people enroll during their initial enrollment period, which runs for seven months: the three months before the month you turn 65, the month itself, and the three months after.

The exact timing matters because late enrollment penalties explore if you miss your window and do not have coverage through an employer or union. These penalties are permanent — they stay on your account for as long as you have Medicare. The penalty for Part B (medical insurance) is 10 percent of the standard premium for each full year you were may be able to access but not enrolled. Part D (prescription drug) penalties work the same way. If you have employer coverage when you turn 65, you can delay enrollment without penalty, but you must enroll within 63 days of losing that coverage.

Key Takeaways

  • You can enroll in Medicare starting three months before you turn 65, during the month you turn 65, or up to three months after — a seven-month window called your initial enrollment period.
  • If you miss this window and do not have employer or union coverage, you will pay a permanent penalty on Part B and Part D premiums for every year you were may be able to access but not enrolled.
  • You can delay enrollment without penalty only if you have health coverage through a current employer or union plan, and you must enroll within 63 days of losing that coverage.
  • People on SSDI for 24 months, those with end-stage renal disease, and those with ALS can start Medicare before 65.
  • If you are still working at 65 and covered by your employer, tell Social Security or Medicare so they do not automatically enroll you and charge you premiums you may not need.

Your initial enrollment period: the seven-month window

Your initial enrollment period begins three months before the month you turn 65. If you turn 65 in June, you can enroll starting in March. The window closes three months after your birthday month — so if you turn 65 in June, you can enroll through September. This is the easiest time to enroll because you have no penalty risk as long as you sign up sometime during these seven months.

You do not have to enroll on your birthday or wait until the month you turn 65. Many people enroll in the month before their birthday to make sure everything is in place. 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.

What happens if you miss your initial enrollment period

If you do not enroll during your seven-month window and you do not have coverage through an employer or union, you will owe a late enrollment penalty. For Part B, the penalty is 10 percent of the standard monthly premium for each full 12-month period you were may be able to access but not enrolled. If the standard Part B premium is $165 per month and you were may be able to access for three years before enrolling, your penalty would be 30 percent of $165, or about $50 extra per month for life.

Part D (prescription drug coverage) penalties work the same way. If you go 63 days or longer without Part D coverage and you do not have creditable coverage from another source (such as an employer plan or Veterans benefits), you will pay a penalty. The penalty is 1 percent of the national average Part D premium for each month you were without coverage. These penalties are permanent — they do not go away after a certain time.

The only exception is if you have health coverage through a current employer or union. In that case, you can delay Medicare enrollment without penalty. You must enroll within 63 days of losing that coverage. If you lose coverage on a Friday, you have until the following Tuesday to meet the 63-day important date. Keep documentation of when your coverage ended.

Enrolling before 65: disability, ESRD, and ALS

You can start Medicare at any age if you have been receiving SSDI for 24 consecutive months. Your initial enrollment period still runs for seven months, but it is centered on the month you become may be able to access, not on your 65th birthday. If you have been on SSDI for 24 months in March, your enrollment period runs from December through June.

If you have end-stage renal disease (ESRD) — permanent kidney failure requiring dialysis or a transplant — you can start Medicare when ready, regardless of age. Your initial enrollment period is the month you start dialysis or have a transplant, plus the three months before and three months after. If you have ALS (amyotrophic lateral sclerosis), you become Medicare-may be able to access the month your SSDI begins, with the same seven-month enrollment window.

Staying covered if you are still working at 65

If you are still working and covered by your employer's health plan when you turn 65, you do not have to enroll in Medicare right away. You can delay enrollment without penalty as long as your employer coverage continues. However, you should tell Social Security that you are still working and covered, because Medicare may try to enroll you automatically when you turn 65. If that happens, you will start paying Medicare premiums even though you do not need the coverage yet.

When you do leave your job or lose your employer coverage, you have 63 days to enroll in Medicare. Count the day you lose coverage as day one. If you lose coverage on June 15, day 63 is August 17. Enroll by that date to avoid late penalties. If your employer has 20 or more employees, your employer plan is primary and Medicare is secondary — meaning your employer plan pays first. Once you have fewer than 20 employees or you leave the job, Medicare becomes primary.

How to enroll and what you will need

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 option and takes about 10 minutes. You will need your Social Security number, date of birth, and information about any current health coverage you have.

If you are already receiving Social Security benefits, Medicare will contact you automatically about three months before you turn 65. You can accept their offer or make changes to your coverage choices. If you are not yet receiving Social Security, you will need to contact Medicare or Social Security to enroll. Do not wait for them to contact you — it is your responsibility to enroll during your window.

Part A, Part B, Part D: what each covers and when to choose

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 for at least 10 years. You should enroll in Part A even if you are still working, because there is no premium and no penalty for delaying it.

Part B covers doctor visits, outpatient care, and preventive services. Part B has a monthly premium (about $165 in 2024, but varies by income). If you are still working and covered by your employer, you can delay Part B without penalty. If you are not covered by an employer plan, enroll in Part B during your initial enrollment period to avoid the 10 percent permanent penalty.

Part D is prescription drug coverage. You choose a plan from private insurers during your initial enrollment period. If you do not enroll and you do not have creditable coverage from another source, you will pay a 1 percent penalty on the national average Part D premium for each month you were without coverage. This penalty is permanent. If you have coverage through an employer or union, ask whether it is creditable — if it is, you can delay Part D without penalty.

Frequently Asked Questions

Can I enroll in Medicare before my initial enrollment period starts?

No. Your initial enrollment period is fixed: three months before the month you turn 65, the month itself, and three months after. You cannot enroll earlier. If you try to enroll before this window, the system will not accept your process. The only exception is if you are on SSDI, have ESRD, or have ALS — in those cases, your enrollment period is centered on the month you become may be able to access, not on your 65th birthday.

What if I turn 65 while I am still working?

You can delay Part B and Part D enrollment without penalty as long as you have health coverage through your current employer or union. You must enroll within 63 days of losing that coverage. Part A has no premium for most people, so there is no penalty for delaying it, but you should still enroll. Tell Social Security that you are still working so they do not automatically enroll you in Part B and charge you premiums you do not need.

How much is the late enrollment penalty?

For Part B, the penalty is 10 percent of the standard monthly premium for each full year you were may be able to access but not enrolled. If you were may be able to access for three years, your penalty is 30 percent of the standard premium, and you pay it for the rest of your life. Part D penalties are 1 percent of the national average Part D premium for each month you were without coverage. Both penalties are permanent.

Do I have to choose a Part D plan during my initial enrollment period?

You should choose a Part D plan during your initial enrollment period to avoid the late enrollment penalty. However, if you have creditable coverage from an employer, union, Veterans benefits, or another source, you can delay Part D without penalty. Ask your current plan whether it is creditable before you assume you can wait. You have 63 days after losing creditable coverage to enroll in Part D.

What if I miss my 63-day important date after losing employer coverage?

If you miss the 63-day important date, you will owe a late enrollment penalty. For Part B, the penalty is 10 percent of the standard premium for each year you were may be able to access but not enrolled. For Part D, it is 1 percent of the national average Part D premium for each month you were without coverage. These penalties are permanent and will be added to your premiums for the rest of your life. You can still enroll, but the penalty applies when ready.