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Medigap or Medicare Advantage: how the two paths work in Washington
By Vadim Marusin, licensed Medicare insurance agent in Washington (WAOIC #1365574). Insurer data checked against the state chart current as of October 8, 2026.
The biggest Medicare decision isn't which plan letter to buy. It's whether you stay in Original Medicare and add a supplement, or replace Original Medicare with a private Medicare Advantage plan. This page explains how each path is built so you can see which one fits you.
Two different structures
Path 1: Original Medicare + Medigap + Part D. You keep federal Original Medicare (Parts A and B) as your main coverage. A Medigap policy pays most of what Medicare leaves behind: deductibles, the 20% coinsurance and, depending on the plan, excess charges and foreign emergencies. You add a separate Part D plan for prescriptions.
Path 2: Medicare Advantage (Part C). You still have Medicare and still pay the Part B premium, but a private insurer approved by Medicare administers your coverage instead of Original Medicare. The plan sets its own network, copays and rules within federal limits.
You can't combine them. Medigap only works with Original Medicare, and it's illegal for anyone to sell you a Medigap policy while you're in a Medicare Advantage plan unless you're leaving it.
This site covers Medigap. For a full, unbiased comparison of the Medicare Advantage plans offered in your county, call SHIBA, Washington's free Medicare counseling service, at 1-800-562-6900, or use the plan finder on Medicare.gov.
How they differ in practice
| Original Medicare + Medigap | Medicare Advantage | |
|---|---|---|
| Who pays your claims | Medicare first, then your Medigap insurer | The Medicare Advantage plan |
| Doctors and hospitals | Any provider in the U.S. that accepts Medicare | Set by the plan; many use networks |
| Referrals and prior approval | Not required by Medigap | Set by each plan |
| Monthly cost | Part B premium + Medigap premium + Part D premium | Part B premium + the plan's premium, if any |
| Cost when you use care | Small and predictable (Plan G: the Part B deductible) | Copays and coinsurance up to the plan's yearly limit |
| Prescription drugs | Separate Part D plan | Often included in the plan |
| Changing coverage | Washington: switch Plans B–N any time | During Medicare's enrollment periods |
| Travel within the U.S. | Same coverage everywhere | Depends on the plan's network rules |
When Medigap tends to fit
- You want to choose any doctor or hospital, including specialists or hospitals out of state.
- You split the year between Washington and another state, or travel often.
- You want to know roughly what a bad health year will cost before it happens.
- You live in a rural county where your nearest specialist might be in another county or another state.
The switching question, in Washington
Many people pick a path at 65 and assume they can change later. Here's how it actually works in Washington:
Moving from Medigap to Medicare Advantage is possible during Medicare's enrollment periods. If you do it for the first time and change your mind within 12 months, federal law gives you the right to buy back a Medigap policy with no health questions (a "trial right").
Moving from Medicare Advantage to Medigap later on is the harder direction. Outside a guaranteed-issue situation, a Medigap insurer can ask health questions and decline you. Washington's year-round switching rule protects people who already have Medigap; it doesn't create a free pass from Medicare Advantage into Medigap. See moving from Medicare Advantage to Medigap and guaranteed-issue rights.
That's why the decision at 65, during your Medigap open enrollment, matters more than any later one.
Questions to ask yourself
- Which doctors and hospitals do I use now, and which would I want if I got seriously ill?
- Do I spend months outside Washington?
- Would I rather pay more each month and little when I use care, or less each month and more when I use care?
- If I choose Medicare Advantage now, how would I feel if health questions kept me from moving to Medigap later?
Common questions
Can I have Medigap and Medicare Advantage at the same time?
No. Medigap only pays alongside Original Medicare. If you join a Medicare Advantage plan, a Medigap policy wouldn't pay your claims.
Is Medigap available everywhere in Washington?
Yes. Every Washington county has at least a dozen insurers selling Medigap. See your county.
Do I need a separate drug plan with Medigap?
Yes. Medigap policies sold since 2006 don't include drug coverage. You'd add a stand-alone Part D plan.
Who can give me unbiased help comparing both paths?
SHIBA, the Office of the Insurance Commissioner's free counseling program, at 1-800-562-6900.