Medicare 101

With so many Medicare plans to choose from, we’re here to help you understand your options for your health coverage — from the enrollment process and changing primary care physicians to the types of Medicare plans we accept.

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What is Medicare?

Medicare is government-sponsored health insurance for people ages 65 and older, those with disabilities, and people with End Stage Renal Disease (ESRD). In addition to Original Medicare, you can choose a Medicare Advantage Plan or other types of Medicare health plans.

Medicare Enrollment

Initial Enrollment Period

If you’re eligible for Medicare when you turn 65 and are enrolling for the first time, you will have a 7-month Initial Enrollment Period (IEP) to sign up for Part A and/or Part B, often called Original Medicare.

You can also choose additional coverage at this time, like Part D. Your Initial Enrollment Period begins 3 months before your birth month, includes your birth month, and ends 3 months after your birth month. For example, if you were born in May, your IEP begins in February and ends in August.

Open Enrollment Period, Oct. 15 – Dec. 7

The Medicare Open Enrollment Period (OEP), often called open enrollment, takes place from October 15 – December 7 each year. All changes go into effect on January 1 of the upcoming year.

During this time, you can:

  • Sign up for a new Medicare plan
  • Switch from Original Medicare to Medicare Advantage (MA)
  • Add a Medicare Part D plan to your current Medicare coverage
  • Add a Medicare supplement plan to your current Medicare coverage (not applicable for Medicare Advantage plans)

If you do not choose a new plan during open enrollment, your existing coverage will continue into the following year. If you did not have previous coverage, you could be subject to a surcharge and pre-existing conditions may not be covered by your provider in the future, so it’s important to start planning before you turn 65.

Special Enrollment Periods

You can make changes to your Medicare Advantage and Medicare prescription drug coverage (Part D) when certain events happen in your life, like if you move to a different coverage area or you lose other insurance coverage. These are called Special Enrollment Periods (SEPs). For more details on SEPs visit

Medicare benefits vary from year to year, so be sure to review your Medicare plan materials annually to ensure your current plan still meets your needs. You can look over each year’s Medicare plan at the beginning of October, and we strongly recommend discussing your Medicare options with an insurance agent.

As you re-evaluate your coverage each year, you may find you need to change your plan to:

  • Keep certain benefits
  • Get a higher quality plan
  • Get better prescription drug coverage
  • Keep your doctor in-network

Whether you’re already working with a local Medicare agent, have questions about how to find a Medicare agent, or want to learn more about your options, you can contact our patient enrollment coordinators for assistance.

If you miss open enrollment in the fall, you still may be able to enroll in a different plan during the Medicare Advantage Open Enrollment Period (MAOEP), which runs from January 1 – March 31.

During MAOEP, beneficiaries who already have a Medicare Advantage plan can switch insurance providers and enroll in another Medicare Advantage plan. You can also disenroll from your current plan and revert to Original Medicare, with the option to enroll in a Part D prescription drug plan.

Learn more about changing your Medicare Advantage plan


Changing your primary care physician on Medicare

There are many reasons to switch primary care providers, like changes in your insurance, level of service, or a closing or moving practice. You may want to find a PCP that focuses on the needs of seniors, when preventive and coordinated care becomes crucial to your health.

Good news! If you have Original Medicare (Part B), you can go to any One Medical practice.* We also accept various Medicare Advantage plans — contact your local One Medical office to see which Medicare Advantage plans we accept.

Medicare plans we accept

Original Medicare consists of Parts A and B, and many participants opt to add Part D to their plan as well. Original Medicare (Part B) is accepted at all One Medical practices.* Original Medicare consists of one or more of the following parts:


Part A is automatic and includes payments for treatment in a medical facility, such as a hospital stay.


Part B is automatic if you do not have other healthcare coverage, such as through an employer or spouse, and covers outpatient medical services.


Part C is also called Medicare Advantage. It is an alternative to Original Medicare, offered by private health insurance companies and includes Parts A and B.


Part D covers prescription drug benefits.


Medicare Advantage

Medicare Advantage plans are offered by private insurance providers. These plans include Parts A and B and often come with additional benefits, such as vision and hearing, prescription drug coverage (Part D), or gym memberships.

One Medical Seniors offices are dedicated to adults 65 and over and for those on Medicare. These offices can be found at select locations in 7 states. See which Medicare Advantage plans are accepted at One Medical Seniors offices.

One Medical offices see patients of all ages. These offices can be found in many U.S. cities. See which Medicare Advantage plans are accepted at One Medical offices.

Insurance FAQs

* excluding San Diego, CA

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