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How do I enroll in Medicare?

What you need to know about enrolling in Original Medicare, Advantage plans and the supplemental coverage that's available

Louise Norris

How do I enroll in Medicare?

With Original Medicare (Medicare Part A and B), enrollment can be as easy as opening your mail and putting your Medicare card in your wallet. For some other plans, you’ll have to do a bit more to enroll, but it’s important to thoroughly research your options before enrolling.

Enrolling in Original Medicare

When it comes to Original Medicare, enrollment could be a piece of cake. If you’re already receiving Social Security or Railroad Retirement Board benefits and you’re a U.S. resident, the government automatically enrolls you in both Medicare Part A and Medicare Part B at age 65. About three months before your 65th birthday, your Medicare card will arrive in the mail with instructions.

At this point, you’ll have the option to turn down Medicare Part B (which has a monthly premium — for most enrollees, it’s $174.70/month in 2024, whereas Medicare Part A is premium-free for most enrollees). But you probably won’t want to do that unless you have coverage from your own or your spouse’s current employer, and the employer has at least 20 employees. That’s a valid reason for delaying your enrollment in Medicare Part B.

If you decide to not enroll in Part B, but plan to enroll later, know that you could end up having to pay a higher premium – 10% higher for each year you could have enrolled, but didn’t. The penalty doesn’t apply, however, if you delayed your Part B enrollment because you had employer-sponsored health insurance from your (or your spouse’s) current employer, including TRICARE from current military employment.

If you are turning 65, but you’re not yet receiving Social Security or railroad retirement benefits, you won’t be automatically enrolled in Original Medicare. Instead, you’ll be able to enroll during a seven-month open enrollment period that begins three months before the month you turn 65, and includes the month you turn 65 and the three following months. So if you’ll be 65 on July 14, your open enrollment period will be April, May, June, July, August, September, and October.

If you haven’t yet enrolled in Social Security but are eligible and want to begin receiving benefits, you can enroll online, or at a local Social Security office. Be sure you understand how your benefits depend on the age at which you start receiving them, and there’s no right or wrong answer in terms of when you should activate your benefits.

If you’ll be eligible for railroad retirement benefits, you can enroll by contacting your Railroad Retirement Board field office.

Beneficiaries whose incomes and assets qualify them for a Medicare Savings Program (MSP) are enrolled in Medicare Part B automatically.

Enrolling in Medicare Advantage

Medicare Advantage allows you to obtain your Medicare coverage from a private insurance company, instead of directly from the federal government. Instead of a regular Medicare ID card, you’ll use the insurance card issued by the private Medicare Advantage insurer when you obtain medical treatment.

To join a Medicare Advantage plan, you must have or be eligible for Original Medicare (Part A and Part B) coverage and live in an area where a Medicare Advantage Plan is offered. (A plan may be offered in a state, but not in every county in that state; some rural areas of the U.S. don’t have any Medicare Advantage plans available at all, although Medicare Advantage plans are available in most of the country.)

There are also limits on when you can enroll in a Medicare Advantage plan. You can enroll when you’re first eligible for Medicare. If you have Social Security Disability Insurance, you can enroll in the 25th month of your disability or during the three months before or after that month. Each year, you’ll have the option to switch to a different Medicare Advantage plan (or switch from Original Medicare to a Medicare Advantage plan) during the annual open enrollment period that runs from October 15 to December 7, with coverage effective January 1.

If you plan to enroll through a carrier’s website, you may want to compare Medicare Advantage Plans first at Medicare’s site, so that you’re aware of all the available options.

Medicare Advantage plans must cover all of the services that Medicare Part A and Part B would cover, albeit with different out-of-pocket costs. Most Advantage plans also include Part D prescription drug coverage, making the plan an all-in-one approach to Medicare (as opposed to needing to purchase a Part D plan and a Medigap plan if you have Original Medicare). But there are pros and cons either way.

It’s important to understand that you may also need long-term care insurance to guard against future costs, because long-term custodial care isn’t covered by Original Medicare or Medicare Advantage.

Note that although your Medicare Advantage plan wraps Medicare Part A and Part B into one private plan, you’ll continue to pay your Medicare Part B premium in addition to your Medicare Advantage premium. For most enrollees, Part B premiums are deducted from Social Security checks, although you’ll have to pay it directly if you’re not receiving Social Security (for 2024, the Part B premium for most enrollees is $174.70/month; some Medicare Advantage plans offer a “giveback” rebate that pays a portion of the Part B premium, but this is fairly rare).

How can I make changes to my Medicare Advantage coverage?

The fall open enrollment period, which runs from October 15 to December 7 each year, is an opportunity to switch to a different Medicare Advantage plan or switch to Original Medicare if you think it would serve you better.

If you are already enrolled in a Medicare Advantage plan — even if you just signed up during the most recent annual enrollment period and your coverage only took effect on January 1 — you can switch to a different Advantage plan or Original Medicare during the annual Medicare Advantage open enrollment period. This window runs from January 1 to March 31, and has been available since 2019. It only applies to people already enrolled in Medicare Advantage plans — a person with Original Medicare cannot switch to a Medicare Advantage plan during this window, and a person with a stand-alone Part D plan cannot switch to a different plan during this window. Instead, those enrollees would need to use the annual enrollment period in the fall to make a plan change.

If you already have a Medicare Advantage plan and want to switch to a different Advantage plan during general open enrollment or the Medicare Advantage open enrollment period, your existing plan will disenroll you with no lapse in coverage. Any changes you make during the fall open enrollment period will take effect January 1. If you make a change during the Medicare Advantage open enrollment period, it will take effect the first of the following month.

Ready to enroll in new Medicare Advantage or Part D coverage? Discuss your plan options right now with a licensed Medicare advisor. Call 1-844-309-3504.

Enrolling in Medicare Part D

Medicare Part D covers prescription drugs. You can add a stand-alone prescription drug plan (PDP) to augment your Medicare A and B, or you can choose a Medicare Advantage plan that provides all of the benefits of Medicare A and B, plus prescription drugs and often other benefits as well.

You’re first eligible to enroll in Part D when you’re first eligible for Medicare. When you apply, you will enroll in a private plan and must enroll during a seven-month period that starts three months before the month that you reach age 65. If you don’t enroll during this period, you may pay a late-enrollment penalty that will raise your Part D premium when you do decide to purchase coverage (the late enrollment penalty doesn’t apply if you had creditable drug coverage during the time that you delayed your Part D enrollment).

If you’re Medicare-eligible because you’re disabled AND you’ve reached age 65, you can enroll in a Part D plan, switch Part D plans, or drop your Part D plan during this seven-month period.

If you’re newly eligible because you’re disabled, you can enroll starting 21 months after you began receiving RRB or Social Security benefits and have through the 28th month to enroll (in other words, it’s a seven-month enrollment window, just like a person has around their 65th birthday). Your Part D coverage will start at the beginning of your 25th month of receiving RRB or Social Security benefits, or the month following your enrollment if you sign up in the latter months of the enrollment window.

If you don’t have Part A or Part B and you enroll in either one during the Part B General Enrollment Period, you’ll have an opportunity to enroll in Part D as well. But if you already have Part A only and you use the General Enrollment Period to sign up for Part B, you will have to wait until the fall open enrollment period to enroll in Part D. This is because Part D is available to a person who is enrolled in Part A or Part B, which means that the person had the chance to sign up for Part D when they first enrolled in Part A, and will thus have to wait until the fall enrollment window to get Part D, since they’re not newly eligible.

And if, later on, you want to change to a different Part D plan, you can do that during Medicare’s Open Enrollment period that runs from October 15 to December 7 each year.

If you’re enrolled in a Medicare Advantage plan and use the Medicare Advantage open enrollment period (January 1 to March 31) to switch back to Original Medicare, you’ll also have the option to sign up for a Part D plan to supplement your Original Medicare coverage.

After you’ve chosen from the various PDP offerings, you can enroll by:

  • calling 1-800-MEDICARE to locate PDPs in your area
  • logging in to Medicare’s Prescription Drug Plan Enrollment Center
  • filling out the paperwork sent by mail from Medicare, or
  • calling the private insurer with the specific PDP you want to join.
  • calling one of’s partners at 1-844-309-3504 to discuss your coverage options with a licensed agent.

Once you apply for Plan D, it generally takes about five weeks for your membership card to arrive. During that time, if you need prescription medications, most pharmacies will accept the initial letter you received from Medicare acknowledging your upcoming membership, or an enrollment confirmation number.

Enrolling in Medigap

During your initial Medigap enrollment period (the six months starting with the month you’re at least 65 years old and enrolled in Medicare A and B) you can’t be denied Medigap coverage or be charged more for the coverage because of a past medical condition.

If you’re under 65 and eligible for Medicare because of a disability, the majority of the states provide at least some sort of guaranteed issue period during which you can purchase a Medigap plan, but the consumer protections vary considerably from one state to another. In most of the states that do guarantee access to Medigap plans for people under 65, the insurers are allowed to charge additional premiums for people under 65. You can click on a state on this map to see how Medigap plans are regulated in the state.

If you miss your initial Medigap enrollment period, you may still be able to buy a policy, but a carrier may charge you higher premiums. Or worse, a carrier could decline to issue a Medigap policy entirely. But some states have consumer protections that require guaranteed issue access to at least some Medigap plans:

  • In New York, and Connecticut, Medigap plans are not medically underwritten, regardless of when an applicant enrolls.
  • Massachusetts has an annual guaranteed-issue Medigap open enrollment period that runs from February 1 through March 31.
  • Maine requires each Medigap insurer to designate one month per year when all applicants have guaranteed issue access to at least Medigap Plan A.
  • Missouri has an “anniversary rule” that allows Medigap enrollees to switch to the same letter plan with a different Medigap insurer, guaranteed issue, during the 30-day period preceding the policy anniversary.
  • Seven states (California, Idaho, Illinois, Oregon, Nevada, Louisiana, and Kentucky) have “birthday rules” that allow Medigap enrollees a time-limited window around their birthday each year when they can switch, without medical underwriting, to another Medigap plan with the same or lesser benefits.
  • In Washington state, people already enrolled in Medigap plans can to switch to another Medigap plan at any time (guaranteed-issue), as long as they’ve had coverage for at least 90 days. People with Medigap Plan A are limited to switching to only another Plan A. But people with Medigap Plans B through N can switch to any other Plan B through N.

To find out about Medigap policies in your state, contact your State Department of Insurance or your State Health Insurance Assistance Program, or call 1-844-309-3504 to speak with one of our partners, who can help you find a plan in your area.

Louise Norris is an individual health insurance broker who has been writing about health insurance and health reform since 2006. She has written dozens of opinions and educational pieces about the Affordable Care Act for Her state health exchange updates are regularly cited by media who cover health reform and by other health insurance experts.

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