The Basic Rule for Medicare Part C

To enroll in Medicare Part C (also called Medicare Advantage), you must already have Medicare Part A and Part B. You also must live in the service area of the plan you want to join. Beyond that, most people aged 65 and older who have Part A and Part B can choose a Part C plan — there is no separate income or health requirement to join.

Part C is an alternative way to receive your Medicare benefits. Instead of using Original Medicare (Part A and Part B), you use a private insurance company that contracts with Medicare. The rules about who can join are straightforward, but the timing of when you can join matters a great deal.

Key Takeaways

  • You must have Medicare Part A and Part B before you can enroll in Part C; you cannot skip directly to Part C.
  • You must live in the service area of the specific plan you choose, which varies by insurance company and plan.
  • Most people 65 and older are not turned down for Part C based on health or income, but some plans may have restrictions for certain conditions.
  • You can enroll during your Initial Enrollment Period (when you first turn 65), during the Annual Enrollment Period (October 15 to December 7 each year), or during other special windows if you have a may have access to life event.
  • If you miss your Initial Enrollment Period and do not have continuous coverage, you may pay a late penalty when you eventually join.

You Must Have Part A and Part B First

Part C is not a replacement for getting Part A and Part B — it is a different way to use them. You cannot enroll in Part C unless you are already enrolled in both Part A (hospital insurance) and Part B (medical insurance). If you have not yet signed up for Part A and Part B, you need to do that first through Social Security or Medicare.gov.

Once you have Part A and Part B, you can then choose to switch to a Part C plan. If you are already in Original Medicare and want to move to Part C, you can do so during the Annual Enrollment Period or during certain other windows. The timing depends on when you first became may be able to access for Medicare.

Living in the Plan's Service Area

Every Medicare Advantage plan serves a specific geographic area — usually a county or a group of counties. You must live in that area to join the plan. Service areas vary widely: some plans cover a single county, while others cover multiple counties or an entire state.

Before you choose a plan, check whether your home address falls within its service area. You can search for plans in your area on Medicare.gov by entering your zip code. If you move, you may need to switch plans, because your new address might not be in your current plan's service area. A move is one of the may have access to life events that lets you change plans outside the Annual Enrollment Period.

Age and Citizenship Requirements

You must be 65 or older to enroll in Part C. You also must be a U.S. citizen or a lawful permanent resident who has lived in the United States for at least five consecutive years. These are the same requirements as for Part A and Part B.

If you are under 65 and have Medicare because of a disability or end-stage renal disease, you can also enroll in Part C, provided you meet the service area requirement and have both Part A and Part B.

Health Status and Pre-Existing Conditions

Medicare Advantage plans cannot turn you down or charge you more based on your health history or pre-existing conditions. This protection is federal law. Even if you have diabetes, heart disease, cancer, or any other condition, a plan cannot deny you enrollment or penalize you with higher premiums.

However, some plans do have restrictions on certain treatments or specialists. For example, a plan might require you to use doctors within its network, or it might require prior approval before you see a specialist. These are plan rules, not health-based rejections. If you have specific health needs, review the plan's network and coverage rules before you enroll to make sure the plan will work for you.

When You Can Enroll

The timing of your enrollment matters. Your Initial Enrollment Period is the seven-month window that begins three months before the month you turn 65. If you enroll during this window, your coverage can start as early as the month you turn 65. If you miss this window and do not have other coverage, you may face a late penalty.

The Annual Enrollment Period runs from October 15 to December 7 each year. During this time, anyone with Medicare can switch from Original Medicare to a Part C plan, or from one Part C plan to another. Coverage changes made during this period take effect on January 1 of the following year.

You can also enroll outside these windows if you have a may have access to life event — such as moving out of your plan's service area, losing employer coverage, or becoming newly may be able to access for Medicaid. These events open a special enrollment window, usually lasting two months. You must report the event to Medicare to use this window.

Income and Financial information

There is no income limit to enroll in Part C. You can have any income level and still join a Medicare Advantage plan. However, if your income is low, you may be able to receive help paying your premiums and out-of-pocket costs through programs like the Low-Income Subsidy (also called Extra Help) or your state's Medicaid program.

Some Part C plans also offer reduced premiums or additional benefits (such as dental or vision coverage) for people with lower incomes. When you search for plans, you can filter by plans that offer these benefits. The amount of help you receive depends on your income and assets, which vary by state and year.

Frequently Asked Questions

Can I enroll in Part C if I have Original Medicare?

Yes. If you already have Part A and Part B through Original Medicare, you can switch to a Part C plan during the Annual Enrollment Period (October 15 to December 7) or during a special enrollment window if you have a may have access to life event. Your new coverage will begin on January 1 if you enroll during the Annual Enrollment Period.

What happens if I miss my Initial Enrollment Period?

If you miss your Initial Enrollment Period and do not have continuous coverage, you may owe a late penalty. The penalty is a percentage of the Part B premium and stays with you for as long as you have Medicare. You can still enroll in Part C during the Annual Enrollment Period or if you have a may have access to life event, but the penalty applies.

Can a Part C plan deny me because of my age?

No. Once you are 65 or older and have Part A and Part B, you cannot be denied enrollment in a Part C plan based on age. Age discrimination in Medicare enrollment is illegal. The only reasons a plan can deny you are if you do not live in its service area or if you do not have both Part A and Part B.

Do I need to answer health questions to enroll in Part C?

No. Part C plans cannot ask you health questions or require a medical exam before you enroll. They also cannot use your health history to decide whether to accept you or to set your premium. This is true even if you have serious or chronic conditions.

What if I move to a different state?

If you move, your current Part C plan may no longer serve your new address. A move is a may have access to life event that lets you change plans outside the Annual Enrollment Period. You have two months from the date you move to switch to a plan in your new service area. Contact your current plan or Medicare.gov to find plans available at your new address.