When a beneficiary first enrolls in Part B at age 65 or older, a six-month Medigap Open Enrollment Period provides guaranteed issue at standard rates regardless of health history. That window is a one-time event. If the beneficiary instead chooses Medicare Advantage and later wants to switch back after that period has expired, guaranteed-issue protections are available only in limited circumstances: during the first 12 months of Medicare Advantage enrollment under the "trial right," or when the Advantage plan terminates or leaves the service area. Outside those situations, insurers can require applicants to answer health questions and can deny coverage or charge higher premiums based on pre-existing conditions such as diabetes, heart disease, COPD, or prior cancer.
The 71-year-old's experience reflects that dynamic. Having passed her initial enrollment window and the 12-month trial period, she faced underwriting when she applied for Medigap. Three health questions were enough to stop the process, leaving her in her Advantage plan without the supplemental coverage she sought.
Four states — New York, Connecticut, Massachusetts, and Maine — require year-round guaranteed-issue access to Medigap regardless of health status, keeping the switch-back door permanently open. Minnesota is scheduled to join them in August 2026. In the remaining states, the interaction between Advantage enrollment timing and Medigap underwriting creates a one-way door that many enrollees do not see until a health change makes them try to walk back through it.