You cannot keep both
A Medigap policy works with Original Medicare. It does not work with Medicare Advantage. To use a Supplement, you first have to be in Original Medicare, Parts A and B. If your Advantage plan includes drug coverage, that drug coverage ends when the plan ends. You would then look at a separate Part D plan.
When you can leave Medicare Advantage
Annual Enrollment is October 15 – December 7. A change then usually starts January 1. If you are already in a Medicare Advantage plan, Medicare Advantage Open Enrollment is January 1 – March 31, and you can make one change back to Original Medicare. Other Special Enrollment Periods depend on facts such as a move. The enrollment window worksheet is a sketch of the dates. It is not a decision from Medicare.
Buying the Supplement is the harder step
The main time a company must sell you a Medigap policy without health questions is Medigap Open Enrollment. That is the six months starting the month you are 65 or older and enrolled in Part B. If that window has passed, a company in California can generally ask health questions, charge more, or say no. A few guaranteed-issue situations are different. One is a trial right: you joined Medicare Advantage when you first became eligible at 65 and you leave within 12 months, or you dropped a Medigap policy to try Advantage for the first time and you are still inside 12 months. Confirm the right that fits you before you drop the Advantage plan.
The Birthday Rule is not this path
California’s Birthday Rule is a 60-day window that starts on your birthday if you already have a Medicare Supplement. It lets you apply for equal or lesser benefits, generally without health questions. It does not apply because you have Medicare Advantage. Read when health questions can still apply and the Birthday Rule before you treat them as the same thing.
Check the doctors before you drop anything
People make this change because a doctor or hospital is outside the Advantage network. Write the names down and ask whether those offices accept Original Medicare. A Supplement does not add doctors. It helps pay some costs after Original Medicare. Use questions for the office, then Talk with Alan if you want those facts lined up. This website does not enroll you.
Common questions
- Can I switch from Medicare Advantage to Medigap during fall Open Enrollment?
- You can usually leave the Advantage plan during Annual Enrollment, October 15 through December 7. Buying a Medigap policy is separate. If your Medigap Open Enrollment has ended, the company may ask health questions.
- Does the California Birthday Rule let me leave Medicare Advantage?
- No. The Birthday Rule is for people who already have a Medicare Supplement. It is not a path from Medicare Advantage.
- Will I still have drug coverage?
- Not automatically. If the Advantage plan included Part D, that coverage ends when the plan ends. You would choose a stand-alone Part D plan. A gap in drug coverage can lead to a late penalty later.
My Medicare Checkup
Use My Medicare Checkup for your own doctors, prescriptions, and costs.
Start My Medicare CheckupThen get your summary, or talk with Alan.
2026 figures
Medigap Open Enrollment window
The 6-month Medigap window after you are 65 and enrolled in Part B — not the Birthday Rule.
Worksheet
Which enrollment window am I in?
See whether a first-time, fall, or other enrollment window may be open on the date you check.