When You Can Enroll in Medicare: Age, Work History, and Disability Rules

Who Medicare Covers and When

Medicare is a federal health insurance program run by the Centers for Medicare & Medicaid Services (CMS). You can enroll when you turn 65, or earlier if you have been receiving Social Security Disability Insurance (SSDI) for 24 months, or if you have end-stage renal disease or ALS. Most people become covered on the first day of the month they turn 65, or the month after they meet the disability requirement.

The program has four parts — Part A (hospital insurance), Part B (medical insurance), Part D (prescription drug coverage), and Part C (Medicare Advantage plans) — and each has its own enrollment window. Missing your window can mean paying a penalty for the rest of your life, so the timing matters.

Key Takeaways

You become covered at 65 if you have worked and paid Medicare taxes for at least 10 years, or if your spouse has and you are at least 62.
You can enroll starting three months before the month you turn 65 and ending three months after, but coverage does not start until the month you turn 65 or later.
If you are still working at 65 and have health insurance through your employer, you may delay Part B without penalty if your employer has 20 or more employees.
People under 65 who have received SSDI for 24 months, or who have end-stage renal disease or ALS, can enroll at any time.
Late enrollment penalties explore to Part B and Part D if you do not sign up during your window, and those penalties stay with you permanently.

Age 65 and Work History Requirements

The standard path to Medicare is turning 65. You must have worked and paid Medicare taxes (the 1.45 percent withheld from your paycheck) for at least 10 years — not necessarily consecutive — to cover yourself. If you have not worked that long, you may still be covered under your spouse's work record if they have the 10 years and you are at least 62.

If you are a government employee who did not pay Medicare taxes, you may still be covered at 65 if you have 30 quarters of Medicare-covered work at some point in your life. A quarter is roughly three months of work in a calendar year, so 30 quarters is about 7.5 years.

You do not have to be retired to enroll at 65. You can keep working and keep your employer health insurance while also enrolling in Medicare. However, the rules about which plan to choose first depend on your employer's size and your age.

Enrollment Windows and When Coverage Starts

Your Initial Enrollment Period is seven months long: it starts three months before the month you turn 65 and ends three months after. For example, if you turn 65 in June, you can enroll from March through September. You should enroll during this window even if you do not plan to use Medicare right away, because waiting can trigger penalties.

Coverage begins on the first day of the month you turn 65, or the first day of the month after you meet the requirement (for disability or end-stage renal disease). If you enroll in January but do not turn 65 until March, your coverage starts March 1, not January 1.

If you miss your Initial Enrollment Period, you enter the General Enrollment Period, which runs January 1 through March 31 each year. Coverage under General Enrollment does not start until July 1 of that year, and you will owe a penalty on Part B for every month you were not covered.

Disability and End-Stage Renal Disease

You can enroll in Medicare before 65 if you have been receiving SSDI for 24 consecutive months. The 24-month clock starts the month you are approved for disability, not the month you applied. Once you have been on SSDI for 24 months, you become covered automatically — you do not have to enroll, though you should confirm your coverage with Social Security.

If you have end-stage renal disease (permanent kidney failure requiring dialysis or transplant), you can enroll as soon as you are diagnosed, even if you are under 65 and not on disability. Coverage begins the first day of the month you are diagnosed or the month after, depending on when you enroll.

If you have ALS (amyotrophic lateral sclerosis), you can enroll when ready upon diagnosis. You do not have to wait for SSDI approval. Coverage starts the month you enroll or the month after.

Still Working at 65: Employer Coverage and Delayed Enrollment

If you are still working at 65 and your employer has 20 or more employees, you can delay enrolling in Part B without penalty. Your employer health insurance is considered primary, and Medicare is secondary. You have eight months after you leave your job or your employer coverage ends to enroll in Part B without penalty — this is called the Special Enrollment Period.

Part A (hospital insurance) is usually free at 65 if you have the work history, so most people enroll in Part A even if they delay Part B. However, if you are covered by your spouse's employer plan and your spouse is still working, different rules explore — you may want to check with Social Security before enrolling.

If your employer has fewer than 20 employees, Medicare becomes primary at 65, and you should enroll in Part B during your Initial Enrollment Period to avoid penalties, even if you have employer coverage.

Late Enrollment Penalties

If you do not enroll in Part B during your Initial Enrollment Period and you do not have a Special Enrollment Period (such as employer coverage), you will owe a late enrollment penalty. The penalty is 10 percent of the standard Part B premium for each full year you were not enrolled. If the standard premium is $165 per month and you were late by three years, you would pay an extra $49.50 per month for life.

Part D (prescription drug coverage) has the same penalty structure. If you go 63 days or more without creditable drug coverage and then enroll, you pay a penalty based on how long you were uncovered. Unlike Part B, the Part D penalty recalculates each year based on the current premium, so it can change.

The only way to avoid these penalties is to enroll during your window or to have a may have access to reason for a Special Enrollment Period — such as employer coverage, COBRA, or a change in your life situation like losing a job or moving out of state.

Medicare Advantage and Prescription Drug Plan Enrollment

Part C (Medicare Advantage) and Part D (prescription drug plans) have their own enrollment windows. If you are turning 65, you can enroll in these plans during your Initial Enrollment Period along with Part A and Part B. If you already have Medicare, you can change plans during the Annual Enrollment Period, which runs October 15 through December 7 each year.

If you have creditable drug coverage through an employer or union plan, you do not have to enroll in Part D right away. However, once that coverage ends, you have 63 days to enroll in Part D without penalty. If you wait longer, the penalty applies.

Frequently Asked Questions

Can I enroll in Medicare before I turn 65?

Yes, if you have been on SSDI for 24 months, or if you have end-stage renal disease or ALS. You can also enroll at 62 if your spouse is 65 or older and has the required work history. Otherwise, you must wait until 65.

What happens if I miss my enrollment window?

You can enroll during the General Enrollment Period (January 1 through March 31), but coverage does not start until July 1, and you will owe a late enrollment penalty on Part B and Part D for every month you were not covered. The penalty stays with you permanently.

Do I have to retire to enroll in Medicare?

No. You can keep working and keep your employer health insurance while enrolling in Medicare at 65. If your employer has 20 or more employees, you can delay Part B without penalty as long as you are covered by the employer plan.

What if I worked for the government and did not pay Medicare taxes?

You may still be covered at 65 if you have 30 quarters of Medicare-covered work at some point in your life. Contact Social Security to verify your work record before your 65th birthday.

Does my spouse's work history count toward my coverage?

Yes. If your spouse has 10 years of Medicare-covered work and is at least 62, you can be covered under their record at 65, even if you have not worked that long yourself. You do not have to be married currently — divorced spouses can also be covered this way.

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.