Medicare Supplement (Medigap) plans in Washington State

Medicare Supplement insurance — usually called Medigap — is private coverage that pairs with Original Medicare (Parts A and B). Instead of replacing Medicare, it fills the gaps: the deductibles, copayments and coinsurance you’d otherwise pay yourself. You then add a standalone Part D drug plan for prescriptions. The Washington State Office of the Insurance Commissioner regulates the policies; the benefits inside each plan letter are set federally.

How Medigap is different from Advantage

The plans Washingtonians actually buy

Plan G covers everything Original Medicare leaves behind except the Part B deductible ($283 in 2026). Plan N costs less in exchange for small office and emergency copays and no coverage of Part B excess charges. High-deductible Plan G has a much lower premium and a deductible you pay first. Plan F still exists for people who were eligible before 2020 but cannot be sold to anyone newer. Because benefits are standardized, we compare companies on price and on how fast they have raised it.

When you can buy one without health questions

• Your six-month open enrollment. It starts the month you are 65 or older and enrolled in Part B. During it, every plan a company sells is guaranteed available regardless of health.
• Already have a Medigap policy? Any time. Washington law lets an existing Medigap policyholder move to another Medigap plan, from the same company or a different one, at any point in the year without medical underwriting. The single exception is Plan A: if you hold Plan A, you can move only to another Plan A. Our switching guide explains what that does and does not let you do.
• Guaranteed-issue events. Losing an Advantage plan or employer coverage through no fault of your own, or using the 12-month trial right after a first Advantage plan, gives you a federal window (generally 63 days) to buy certain plans without underwriting.
• Under 65 on Medicare because of a disability? Federal law does not guarantee you a Medigap open enrollment before 65, and what a Washington carrier will offer you, and at what price, depends on the carrier and current state rules. Ask us or SHIBA before you assume; you get a full open enrollment at 65 either way.
• Coming from Medicare Advantage without one of those events, Washington insurers can use medical underwriting. The year-round rule helps only once you are inside Medigap.

Compare the rate history, not just the first-year price

Because the benefits are standardized, the only real differences between Washington Medigap companies are what they charge and how steeply they raise it later. That second part is public: every carrier files its rate changes with the Office of the Insurance Commissioner, and a policy that looks cheap at 65 can be the expensive one by 75. We publish that filing history on our research site, Washington Medigap rate history, with each figure tied to the filing it came from. Because Washington lets you move without underwriting, a steep increase is a reason to shop, not a trap — why Medigap premiums increase covers the three causes.

Who Medigap tends to suit

People who want maximum freedom to choose doctors and hospitals — UW Medicine or Fred Hutch without a network question, a Seattle specialist from a Ferry County address — predictable costs, and coverage that travels to a second home in Arizona or a grandchild in Idaho. The cost is a monthly premium that rises with age and with the carrier’s filings, softened in Washington by the freedom to move.