Understanding Medigap in Ontario, California (2027)

Wondering whether a Medicare Supplement makes sense in Ontario, California? We explain what the standardized Medigap plans cover, how they pair with Original Medicare and a drug plan, and what to know in San Bernardino County — with no rankings and no sales pitch.

Medicare around Ontario can look different from the county next door, and that's by design: plans are approved county by county, and Ontario sits in San Bernardino County (part of Ontario area).

95 Medicare Advantage plans are available for 2027. About 67% of the county's Medicare members are in a Medicare Advantage plan rather than Original Medicare, among the roughly 276,984 residents who are 65 or older.

You'll see who offers coverage nearby, how the pieces of Medicare fit, what things cost in 2027, when the enrollment windows open, and where to turn for free, unbiased guidance.

Where Medigap fits in your Medicare

Original Medicare (Part A and Part B) pays most of your covered costs — but not all. You're left with deductibles, coinsurance, and copays, and there's no annual out-of-pocket maximum in Original Medicare on its own. That open-ended exposure is the gap Medigap policies are designed to help close.

Medigap policies are sold by private insurers but standardized by the federal government and labeled with letters (such as Plan G or Plan N). Because they're standardized, a given lettered plan covers the same things no matter who sells it — what differs is price and service. Medigap pairs with Original Medicare, not Medicare Advantage, and doesn't include drugs, so people on this path usually add a stand-alone Part D plan.

This guide explains how the standardized plans and your enrollment rights work in Ontario, California. We explain the framework — we don't rank plans or quote specific premiums.

What Medicare costs in 2027

It helps to separate the costs everyone shares from the costs that vary by plan. The program-level numbers here are set nationally — the same whether you're in a big city or a rural county.

Part B premium. Most people pay the standard Part B premium of $202.90 a month in 2026 (2026 amount; 2027 figure will be posted when CMS releases it). Part A is premium-free for most people who worked and paid Medicare taxes long enough.

Part D drug costs. In 2027, a Part D plan's yearly deductible can be no more than $700, and a $2,400 cap limits what you pay out of pocket for covered prescriptions across the year — a real change for anyone with high drug costs.

Higher earners pay more for Parts B and D through an income-related adjustment called IRMAA, which for 2026 starts above $109,000 in annual income for an individual and is based on your 2024 tax return. Most people fall below that line and pay the standard amounts. The 2027 brackets will be posted when CMS releases them.

Plan-specific costs. What an individual plan charges — its premium, deductible, copays, and what it covers — varies by plan and changes yearly. We don't publish those figures or rank plans; Medicare's Plan Finder shows the current details for your situation, and a licensed agent can walk you through them.

Your Medicare enrollment calendar

The dates that follow are set federally, so they don't change from state to state — only your personal timing does.

It starts with your Initial Enrollment Period — the 7-month window around your 65th birthday month — the window around turning 65 when you first sign up. Missing it can mean late penalties that stick around, so it's the one not to sleep on.

After that, the big recurring window is the Annual Enrollment Period, October 15 – December 7, when anyone can join, switch, or drop an Advantage or Part D plan for a January 1 start. And if you're already in an Advantage plan, the Medicare Advantage Open Enrollment (January 1 – March 31) gives you one more chance to change course.

Life events — a move, a loss of other coverage — can also trigger a Special Enrollment Period. The calendar below shows the whole year at a glance.

Getting unbiased help in Ontario

You never have to make these decisions alone, and you don't have to pay for good help. A few free, trustworthy starting points:

Medicare.gov and 1-800-MEDICARE (TTY 1-877-486-2048) are the official sources for plan details and the Plan Finder. Licensed agents can also compare options with you and handle enrollment.

And to be clear about who we are: MyMedicarePlans.org is a privately owned, independent educational resource. We are not Medicare, not a government agency, and not affiliated with one. We publish plain-language information to help you get oriented — then point you to the official sources and licensed professionals for decisions about specific plans.

Latest Medicare Supplement guides for Ontario

More California Medicare Supplement guides