The transition from Medicaid expansion to Medicare creates a critical coverage gap that affects healthcare access for millions of lower-income older adults. This administrative barrier could determine whether vulnerable populations maintain comprehensive coverage or face unexpected medical costs during a pivotal life transition. Analysis of enrollment data from 31 states plus DC reveals that asset testing requirements significantly reduce dual Medicare-Medicaid coverage retention. Among adults who previously had Medicaid expansion coverage, those in states requiring asset tests for the Medicare Savings Program were 12 percentage points less likely to maintain Medicaid benefits after Medicare enrollment compared to states waiving these requirements. The study tracked beneficiaries who entered Medicare in 2018, examining coverage patterns through their first year. States without asset testing—Arizona, Connecticut, Delaware, New York, Oregon, Vermont, and DC—demonstrated substantially higher rates of continuous dual coverage. This coverage gap represents more than administrative complexity; it translates to real-world barriers for prescription drugs, long-term care, and out-of-pocket medical expenses. The findings illuminate a policy lever that states control but may not fully recognize. Asset testing, while intended to target benefits, appears to create administrative friction that prevents eligible individuals from accessing coverage they qualify for financially. For the aging population, this represents a critical juncture where policy design directly impacts healthcare accessibility and financial protection during the Medicare transition period.