Who must have Medicare

Medicare is required if you are 65 or older and a U.S. citizen or permanent resident who has lived in the country for at least five years. You do not have a choice about whether to sign up — if you meet these conditions, you are expected to enroll during your may be able to access window or face a penalty on your premiums later.

There are narrow exceptions. If you are still working and your employer offers health insurance, you may be able to delay Medicare Part B (the part that covers doctor visits and outpatient care) without penalty, but only if your employer has 20 or more employees. You will still need to enroll in Part A (hospital insurance) at 65, even if you do not use it yet. If your employer has fewer than 20 employees, you must enroll in both Part A and Part B when you turn 65.

If you are under 65, you may be required to have Medicare if you have received Social Security Disability Insurance (SSDI) for 24 months, or if you have end-stage renal disease or ALS (amyotrophic lateral sclerosis). In these cases, Medicare becomes your primary insurance automatically.

Key Takeaways

  • You must enroll in Medicare at 65 if you are a U.S. citizen or permanent resident who has lived here for five years, unless you are still working and your employer has 20 or more employees.
  • Part A (hospital insurance) is free for most people at 65 and is required even if you do not plan to use it right away.
  • Part B (doctor and outpatient care) costs a monthly premium and you can delay it without penalty only if you have employer coverage with 20+ employees.
  • If you miss your enrollment window, you will pay a permanent penalty on your Part B and Part D premiums unless you have a valid reason for the delay.
  • You can keep working and have Medicare at the same time, but your coverage and costs may change depending on your employer's plan.

What happens if you do not enroll on time

If you do not sign up for Medicare Part B during your initial enrollment window — the three months before the month you turn 65, the month itself, and the three months after — you will pay a late enrollment penalty for as long as you have Medicare. The penalty is 10 percent of the Part B premium for each full year you were may be able to access but did not enroll. If you wait five years to sign up, you will pay 50 percent more than the standard premium, and that extra cost stays with you permanently.

Part D (prescription drug coverage) has the same penalty structure. If you go 63 days or longer without drug coverage and later enroll, you will pay an extra amount each month based on how long you went without it.

The only way to avoid this penalty is to show that you had a valid reason for missing the important date — usually that you were covered by an employer plan or a spouse's employer plan. You will need to provide documentation, such as a letter from your employer or a copy of your health insurance card from that time.

When you can delay Medicare without penalty

If you are still working at 65 and your employer offers health insurance, you may delay Part B without penalty — but only if your employer has 20 or more employees. This is called creditable coverage. You must still enroll in Part A at 65, but you can wait to sign up for Part B until you leave your job or lose your employer coverage.

When you do leave your job, you have eight months from the date your employment ends or your coverage stops to enroll in Part B without penalty. This is called your Special Enrollment Period. You will need to provide proof that you had employer coverage, such as a letter from your employer's benefits department stating the dates you were covered and the number of employees at your company.

If your employer has fewer than 20 employees, you cannot delay Part B. You must enroll at 65 even if you are still working and have employer coverage. The employer plan will be secondary to Medicare, meaning Medicare pays first.

Medicare and working after 65

You can continue working and have Medicare at the same time. Your earnings do not affect your Medicare coverage or your ability to enroll. However, if you are still working and receiving Social Security benefits, your earnings above a certain amount will reduce your monthly benefit check — but this is a Social Security rule, not a Medicare rule.

If you are working and your employer offers health insurance, you can use that as your primary insurance and Medicare as secondary. This means your employer plan pays first, and Medicare covers what the employer plan does not. You will still need to pay your Medicare premiums unless you have arranged otherwise with your employer.

Some employers offer retiree health plans that cover people over 65. If your employer offers this, you can use it alongside Medicare. Make sure you understand which plan is primary and what your out-of-pocket costs will be under both plans.

When you might not need Medicare when ready

If you are 65 or older but still covered by an active employer health plan through your own job, you can delay enrolling in Part B without penalty as long as your employer has 20 or more employees. However, you should still enroll in Part A at 65 because it is free and covers hospital care that your employer plan might not fully cover.

If you are covered under a spouse's employer plan, the same rule applies — you can delay Part B if the employer has 20 or more employees, but you must enroll in Part A. Once you or your spouse leaves that job or the coverage ends, you have eight months to enroll in Part B without penalty.

If you are not yet 65 but receive SSDI, you will be automatically enrolled in Medicare Part A and Part B after 24 months of receiving benefits. You do not need to do anything — it happens automatically. You will receive your Medicare card in the mail before your coverage begins.

How to know if you should enroll now

You should enroll in Medicare at 65 if any of the following is true: you are not working, you are working but your employer does not offer health insurance, your employer has fewer than 20 employees, or you are losing your employer coverage soon. 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.

Your initial enrollment window is seven months long: three months before the month you turn 65, the month itself, and three months after. If you know you will need Medicare, do not wait until the last month — processing can take time, and you want your coverage to start on the first day of the month you turn 65 if possible.

If you are unsure whether your employer coverage counts as creditable coverage, contact your employer's benefits department and ask them directly. They can tell you the number of employees at your company and confirm that your plan meets Medicare's standards. Get this in writing if you can, because you may need it later to prove you had valid coverage.

Questions to ask your doctor or Social Security office

Before you turn 65, ask your current doctor whether they accept Medicare. Not all doctors do, and if yours does not, you will need to find a new primary care doctor or pay out-of-pocket for visits. Ask your doctor's office which Medicare plans they accept — Original Medicare, Medicare Advantage, or both.

If you are still working, ask your employer's benefits department: How many employees does our company have? Does our health plan meet Medicare's standards for creditable coverage? What happens to my coverage if I retire or leave the company? When do I need to enroll in Medicare?

Call Social Security at 1-800-772-1213 to confirm your may be able to access and ask about your enrollment window. They can also tell you whether you have any work credits toward Part A coverage. If you do not have enough credits, you may have to pay a premium for Part A, and Social Security can explain how much.

Frequently Asked Questions

Can I refuse Medicare and keep my employer insurance instead?

If your employer has 20 or more employees, you can delay Part B but not Part A. You must enroll in Part A at 65 even if you keep your employer plan. If your employer has fewer than 20 employees, you cannot refuse Medicare — you must enroll in both Part A and Part B at 65, and your employer plan becomes secondary.

What if I am not a U.S. citizen?

You must be a U.S. citizen or permanent resident who has lived in the country for at least five years to be required to have Medicare at 65. If you do not meet these requirements, you are not required to enroll, but you may be able to purchase Medicare coverage if you meet other conditions. Contact Medicare directly at 1-800-MEDICARE to discuss your situation.

Do I have to enroll in Part D when I turn 65?

Part D is optional, but if you do not enroll when you first become may be able to access and later want it, you will pay a late enrollment penalty. If you do not take any prescription drugs, you can skip Part D, but if you start taking medications later, the penalty will explore. If your employer or retiree plan covers drugs, you may not need Part D.

What if I am still working and do not want Medicare yet?

If your employer has 20 or more employees, you can delay Part B, but you must still enroll in Part A at 65. Part A is free for most people and covers hospital stays. Delaying Part B will not cost you a penalty as long as you enroll within eight months of leaving your job or losing coverage.

How do I prove I had creditable coverage?

Contact your employer's benefits department and ask for a letter stating the dates you were covered, the number of employees at your company, and confirmation that the plan meets Medicare standards. Keep this letter with your Medicare enrollment documents. You may need it if you enroll late and need to prove you had valid coverage.