Medicare Supplement insurance, often called Medigap, fills gaps in Original Medicare. Once you are past your first eligibility window, insurers in most states can ask health questions and decline coverage if you want to change plans. That is why many people keep the Medigap policy they already own even when premiums rise.
Some states add a short annual opportunity to switch Medigap plans without underwriting. These are often called birthday rules or anniversary rules. The details vary by state — and they apply only to people who already have Medigap, not to someone leaving Medicare Advantage for the first time.
Idaho
Idaho gives current Medigap policyholders 63 days beginning on their policy anniversary date to switch to another Medigap plan with the same or lesser benefits without health questions. The new policy must be issued by the same insurer or an affiliate in many cases, and plan letter rules apply — you generally cannot move to a plan with richer benefits under this window.
If you miss the window or want a different carrier, standard underwriting may apply. Mark your policy anniversary on the calendar and request current rates before the period ends.
Oregon
Oregon's birthday rule typically runs for about 30 to 61 days around your birth date (exact timing depends on current state rules and carrier practice). During that window, eligible members can move to an equal or lesser Medigap plan without medical underwriting.
As in Idaho, this is a state-specific protection — not a federal Medicare rule. Confirm the active window and eligible plan moves with a licensed agent or the Oregon Division of Financial Regulation before you apply.
Texas and Washington (CDA markets)
Texas does not offer a Medigap birthday rule like Idaho or Oregon. Outside your initial enrollment or limited guarantee-issue events, changing Medigap carriers or plan letters usually means answering health questions.
Washington has its own Medigap consumer protections, including rules that can allow switching at certain times of year without underwriting. Washington's framework differs from Idaho and Oregon birthday rules — verify current state guidance rather than assuming the same dates apply.
How this differs from Medicare Advantage Open Enrollment
- Medicare Advantage / Part D: Annual Enrollment runs October 15 – December 7 nationwide for people in those plans.
- Medigap: No matching federal annual window. State birthday rules are optional and limited.
- Switching from Advantage to Medigap: Usually requires health questions unless you qualify for a guarantee-issue period.
If you are comparing both paths this fall, see When to compare Medicare Advantage and Medigap side by side.
Before you switch Medigap plans
- Confirm you are inside your state's birthday or anniversary window.
- Compare premiums for an equal or lesser plan letter — not just the monthly rate on marketing mail.
- Make sure the new policy is in force before you drop the old one to avoid a coverage gap.
- Keep a separate Part D plan if your Medigap policy does not include drug coverage.
CDA Insurance helps clients in Idaho, Oregon, Texas, and Washington compare Medigap and Advantage options. Call (800) 884-2343 or use the contact page.
Questions about your Medigap anniversary?
We can explain your state's rules and compare plan letters at no cost to you.
This article is for general education. It is not a plan recommendation, quote, or guarantee of coverage. State rules, plan availability, premiums, and eligibility vary and can change. CDA Insurance LLC is an independent insurance agency and is not connected with the U.S. government or the federal Medicare program. Official program information is available at Medicare.gov or 1-800-MEDICARE.