Medicare in California — plans, enrollment, and how to compare.
What California residents should know about Medicare Advantage, Medicare Supplement, and Part D — and how plan availability is different in California.
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Medicare basics in California
Medicare is a federal program, so the core rules are the same in California as everywhere else — but the specific plans available, premiums, and carrier networks vary by ZIP code and by county.
Most California residents become eligible for Medicare at 65 through Social Security. See our eligibility guide for the full rules including disability and ESRD.
For the 7-month enrollment window timeline, see Turning 65.
What California residents typically compare
- Medicare Advantage — Many California counties have 20-50+ Advantage plans to choose from. Plans, premiums, and extras vary by county.
- Medicare Supplement (Medigap) — Plans are standardized federally, but premium pricing and underwriting rules vary by state. California has its own Medigap pricing rules.
- Part D prescription drug plans — Available statewide, but formularies (covered drug lists) and preferred pharmacy networks differ by plan.
See Advantage vs. Supplement for the side-by-side framework.
California Medigap timing rules
The federal Medigap Open Enrollment window is the same everywhere — 6 months starting the month you turn 65 AND have Part B. During that window, no medical underwriting.
Outside that window, most states (including California unless otherwise noted) allow Medigap carriers to use medical underwriting — meaning they can deny you or charge more based on health. A few states have year-round guaranteed-issue rules. Check California's State Health Insurance Assistance Program (SHIP) for current rules.
See our switching from Advantage to Medigap guide for the timing trap.
How to compare plans in California
- Confirm your ZIP code — plans differ within California by county
- List your prescriptions and check each one on the plan's formulary
- Confirm your doctors are in-network
- Compare premium + deductible + maximum out-of-pocket
- Check extras like dental, vision, hearing for plans you are weighing
- Ask about prior authorization requirements (common on Advantage)
Use our comparison framework to keep it organized.