You can buy any Medicare Supplement sold in your state with no health questions during your Medigap Open Enrollment Period, which lasts six months and starts the month you are 65 or older and enrolled in Part B. The insurance company cannot turn you down, cannot charge you more for your health, and cannot make you wait for coverage of a pre-existing condition, with one exception below. This window happens once.
When your six months start
The clock starts the first day of the month you are both 65 and enrolled in Part B. If you delayed Part B because you were working, your window starts when Part B starts, not at 65. That means people who work to 70 still get their protected window when they finally enroll.
What the protection means
Take someone with diabetes and a heart stent. Inside the window, Plan G at the standard rate, no questions. A year later the same person applying to the same company can be declined. The window removes health from the equation, and it is the best deal in Medicare for anyone with a medical history.
The pre-existing condition wait
A company can make you wait up to six months before covering a condition you were treated for in the six months before the policy started. Medicare itself still covers the condition; the Supplement just does not pay its share until the wait ends. If you had creditable coverage, such as an employer plan, for six months before the policy, the wait is waived.
Your state may give you more
Some states add rules on top of the federal window, such as a yearly birthday window to change plans or protections for people under 65 on disability. Ask me what applies where you live.
Timing it with everything else
Apply for the Supplement before your Part B starts so the policy begins the same day and there is never a gap. Choose the plan letter and the company carefully, because premiums for identical coverage vary widely and a company's history of rate increases matters more than its first-year price.
If your Part B starts within the next six months, or started less than six months ago, request a plan check now. Once the window closes, your choices shrink.