Medigap vs Medicare Advantage in California
How Medigap and Medicare Advantage differ in California: the birthday rule, the 12-month trial right, and when you can switch without health questions.
(updated ) · Khoi Le · Doodle
The short answer
You are choosing between two setups, not two versions of the same plan.
Original Medicare plus Medigap keeps Part A and Part B. You can see any doctor or hospital in the U.S. that takes Medicare. A Medigap policy helps pay Medicare’s deductibles and coinsurance. You pay a separate Medigap premium on top of Part B. Medigap does not cover routine dental or vision. You can buy those separately.
Medicare Advantage (Part C) is a private plan that replaces Original Medicare for Part A and Part B. The plan premium can be $0, but you still pay Part B. For non-emergency care you usually stay in the plan’s network, and the plan can require prior authorization. There is a yearly limit on what you pay for covered Part A and B services. A plan may include vision, hearing, or dental. Not every plan does.
Drug coverage is the other split. With Medigap you buy a Part D plan on your own, and if you skip it without other creditable drug coverage you can owe a late enrollment penalty later. With Medicare Advantage, drug coverage is often included in the same plan.
If a higher monthly premium is workable, Original Medicare plus Medigap is the setup with the widest choice of doctors and the more predictable medical bills. If that premium is not workable, Medicare Advantage is a real alternative, including if you already have health conditions. You can join a Medicare Advantage plan with a pre-existing condition. Medicare does not call either one better.
You cannot have both. It is illegal for anyone to sell you a Medigap policy unless you are switching back to Original Medicare, and Medigap cannot be used to pay a Medicare Advantage plan’s copays, deductibles, or premium.
| Medigap with Original Medicare | Medicare Advantage | |
|---|---|---|
| Doctors | Any that take Medicare | The plan’s network |
| Monthly cost | Part B, plus Medigap, plus a separate Part D plan | Part B, plus the plan premium (sometimes $0). Drugs are often included |
| When you get care | Medigap pays Medicare’s share, based on the plan letter | Copays until the plan’s yearly cap |
| Prior approval | In most cases, no | The plan may require it |
| Dental and vision | Not included | May be included |
When can you get Medigap with no health questions?
The reliable window is once. Medigap open enrollment lasts 6 months, starting the first month you are 65 or older and enrolled in Part B. During those 6 months an insurer cannot use medical underwriting to decide whether to sell you a policy. California uses the same 6 months. After that, an insurer can ask health questions, charge more because of your health, or say no, unless a guaranteed-issue right applies.
Is the trial right “after 11 months”?
No. It is the first 12 months, and you have to leave inside that year.
If you join a Medicare Advantage plan when you first become eligible for Part A at 65, and within that first year you decide you want Original Medicare, you can buy any Medigap policy an insurer sells in California. Your chance to drop the Medicare Advantage plan lasts 12 months after you join it for the first time. You can apply as early as 60 days before that coverage ends, and no later than 63 days after it ends.
There is a second version. If you drop a Medigap policy to try Medicare Advantage for the first time, and you have been in the plan less than a year, you can get the Medigap policy you had before, if that company still sells it. If it does not, federal rules and California law each name a fallback list of plan letters, and the lists are not the same. Check the current list before counting on a specific letter.
Stay past that year and the trial right is gone. Medicare’s guide says if you drop Medigap to join Medicare Advantage and later switch back, you may not be able to get the same policy back, or in some cases any Medigap policy, unless you leave during the trial right period.
Does California’s birthday rule let you move from Medicare Advantage to Medigap?
No. The birthday rule is a Medigap-to-Medigap switch.
If you already have a Medigap policy, California gives you an annual open enrollment of at least 60 days, starting on your birthday, not before it. In that window you can buy another Medigap policy with benefits equal to or less than the one you have. Same company or a different one. The insurer cannot turn you down or charge you more because of your health. A richer plan, for example moving up from Plan N to Plan G, is not what this window is for.
If your only coverage is Medicare Advantage, this rule does not apply.
What else can get you out of Medicare Advantage without health questions?
A few specific events, not a standing right to switch whenever you want:
- The plan leaves your area or stops serving you.
- The plan cuts benefits, or raises the premium or copays past the thresholds in California law.
- The plan drops a doctor who is treating you.
Some of those only open during Medicare’s annual election period, and the plan letters you can buy are set by statute. Check the current list before counting on a letter.
What about dental and vision?
Medicare Advantage plans may include some dental, vision, or hearing benefits. Original Medicare does not cover most dental care or routine eye exams, and a Medigap policy does not add them. With Medigap, those are separate policies if you want them.
A practical way to decide
- In the 6 months after you are 65 and have Part B, Medigap is available without health questions. That window does not reset every year.
- Trying Medicare Advantage at 65 comes with a one-year undo, the trial right. It is not a plan to switch to Medigap several years later.
- Once you have Medigap, California’s birthday rule lets you change Medigap policies later, to equal or lesser benefits, without health questions.
- If the Medigap premium does not fit, compare Medicare Advantage plans on your doctors, prior authorization, the yearly out-of-pocket limit, drug coverage, and whether dental or vision is actually on that plan.
Want help deciding?
Doodle can help decide which is right for you, as well as guide you through Medigap and Medicare Advantage plans that suit your situation and needs.
Where this applies in California
The rules on this page apply statewide, in all 58 California counties: Alameda, Alpine, Amador, Butte, Calaveras, Colusa, Contra Costa, Del Norte, El Dorado, Fresno, Glenn, Humboldt, Imperial, Inyo, Kern, Kings, Lake, Lassen, Los Angeles, Madera, Marin, Mariposa, Mendocino, Merced, Modoc, Mono, Monterey, Napa, Nevada, Orange, Placer, Plumas, Riverside, Sacramento, San Benito, San Bernardino, San Diego, San Francisco, San Joaquin, San Luis Obispo, San Mateo, Santa Barbara, Santa Clara, Santa Cruz, Shasta, Sierra, Siskiyou, Solano, Sonoma, Stanislaus, Sutter, Tehama, Trinity, Tulare, Tuolumne, Ventura, Yolo, and Yuba.
About this page
Written for Doodle by Khoi Le. Checked against Medicare.gov, the CMS Choosing a Medigap Policy guide (March 2026), and California Insurance Code sections 10192.11 and 10192.12, on October 2, 2026.
This page is educational. It is not advice, a quote, or an invitation to enroll. Premiums, networks, and extra benefits change by county and by year.
Sources
- Compare Original Medicare and Medicare Advantage (Medicare.gov)
- How Medigap works (Medicare.gov)
- Compare Medigap plan benefits (Medicare.gov)
- Choosing a Medigap Policy, CMS Product No. 02110, March 2026 (Medicare.gov)
- Understanding Medicare Advantage Plans (Medicare.gov)
- California Insurance Code § 10192.11
- California Insurance Code § 10192.12
- E-1 Population and Housing Estimates for Cities, Counties, and the State, January 1, 2025 and 2026 (California Department of Finance)