Medicare Eligibility and Enrollment

Medically Reviewed by Sarah Goodell on September 15, 2023
5 min read

Who can get Medicare? Basically, three groups are eligible:

  1. Most people 65 and older
  2. People younger than 65 who have certain disabilities and illnesses
  3. People of any age with kidney failure that requires dialysis or a kidney transplant and people with Amyotrophic Lateral Sclerosis (ALS, also known as Lou Gehrig’s disease)

You might assume that signing up for a big government program like Medicare would be confusing. But it's usually easy. Most people are signed up automatically for Original Medicare (Parts A and B).

If you're already getting Social Security checks, you will be automatically enrolled in traditional Medicare. You'll get your Medicare card three months before your 65th birthday. The benefits kick in on the first day of the month of your 65th birthday. Traditional Medicare, which is also called Original Medicare, includes Medicare Parts A and B. Part A is hospital coverage. Part B covers doctor visits, lab tests, and other outpatient services.

If you're not getting Social Security payments already, you have to enroll in Medicare. The Social Security Administration (SSA) handles the enrollment process for Medicare. Call SSA at (800) 772-1213, visit the website (, or apply at your local Social Security office. You have a 7-month enrollment period, beginning 3 months before your 65th birthday, your birthday month, and 3 months after your birthday. Apply early in your enrollment period to be sure that your benefits will start on time.

If you live in Puerto Rico and want Medicare, you need to sign up for Medicare Part B.

No matter how old you are, if you have Lou Gehrig's disease, kidney failure, or certain other disabilities, you are eligible for Medicare. But you might have a waiting period before you can get Medicare benefits. Here are the details.

Lou Gehrig's disease (ALS). As soon as you get Social Security Disability benefits for ALS, you should be automatically enrolled in Medicare. There is no waiting period.

Kidney failure. To qualify, you must have end-stage renal disease and need dialysis or a kidney transplant. Usually, you can't get Medicare until three months after you start dialysis. Once you've been diagnosed with kidney failure, call the Social Security administration at (800) 772-1213 to enroll in Medicare.

Other disabilities for which you get Social Security Disability benefits. You can't get Medicare until two years after you qualify for Social Security Disability. At that point, the Social Security Administration should sign you up automatically.

If you are not getting Medicare coverage and feel that you should, call the Social Security Administration at (800) 772-1213.

Medicare limits your ability to add or drop coverage after official enrollment periods. So pay close attention to Medicare enrollment deadlines. Here are some details:

Initial Enrollment Period. If you are not automatically enrolled, you must sign up during your "initial enrollment period" for Part A with or without Part B. This initial sign-up lasts 7 months, starting 3 months before the month of your 65th birthday and ending 3 months after. During this time, you can sign up for any Medicare coverage you would like. However, if you wait to sign up during the month of your birthday or the 3 months that follow, you will have to wait 1 to 3 months for coverage to begin.

Other enrollment periods. If you did not enroll in Parts A and B during the initial enrollment period, you may do so between Jan. 1 and March 31, with coverage beginning the month after you sign up You may have to pay a higher monthly premium for coverage. There are some exceptions. If you are covered under a group health insurance plan through your job or your spouse's job, or if your employment ends after the initial enrollment period, you may enroll in Medicare during a Special Enrollment Period without having to pay a late-enrollment penalty.

Medicare Advantage Plan (Part C). You may join a Medicare Advantage plan during the 7-month period when you first become eligible for Medicare. These plans may have more benefits and more coverage. You may join, switch, or drop a Medicare Advantage plan between Oct. 15 and Dec. 7. If you’re already enrolled in a Medicare Advantage plan you may change plans or switch to Original Medicare (Parts A and B) and sign up for a Medicare Prescription Drug Plan (Part D) between Jan. 1 and March 31.

Medicare Prescription Drug Plans (Part D). You may join, switch, or drop a drug plan between Oct. 15 and Dec. 7. There is an exception: You may join a 5-star Medicare Prescription Drug Plan, as rated by Medicare, from Dec. 8th to Nov. 30th, but you can only do this once. Go to to see ratings.

What to know about Medicare penalties. If you don't sign up during your initial enrollment period for some programs -- like Medicare Parts A and B and Medicare Prescription Drug Coverage (Part D) -- you might pay a higher monthly fee when you sign up later.

There are some exceptions. If you or your spouse are still working and have insurance coverage through your employer, you generally will not have to pay a late enrollment penalty. To avoid the Part D late enrollment penalty, your drug coverage now through an employer-based health plan must be as good as Medicare's or better. Your employer plan must tell you each year if your plan is “creditable,” which means it provides coverage at least as good as Part D. After insurance from an employer ends, you must sign up for Part B within 8 months and for Part D within 63 days. Keep in mind that an insurance policy from an employer with fewer than 20 employees works differently with Medicare. If you work for a company of that size, you should sign up for Medicare when you are first eligible. You will not incur penalties if you don't, but without Medicare Part B coverage, you could be without coverage for outpatient services.  If you have retiree health insurance through your or your spouse’s former employer, you likely still want to sign up for Medicare. Many retiree health plans act as a “wrap-around” covering the gaps in Medicare coverage. Ask your Human Resources department for assistance.

Sign up for Medigap early. Medigap is private insurance you buy to help pay for additional Medicare costs. If you need a Medigap plan, you should buy it within 6 months of getting Medicare Part B. During that period, you're guaranteed to get any Medigap plan that is available in your state. But if you try to buy it after those 6 months, the insurance company can charge you a higher price or turn you down altogether.