When a TRICARE beneficiary meets Medicare eligibility requirements, they must enroll in Medicare Part A and Part B to remain eligible for most TRICARE plans. If they do not enroll in Medicare Part B, they may lose eligibility for TRICARE benefits. However, there are some exceptions to this rule. Active duty service members, active duty family members, and those enrolled in TRICARE Reserve Select, TRICARE Retired Reserve, TRICARE Young Adult, or the US Family Health Plan can remain eligible for TRICARE without enrolling in Medicare Part B. TRICARE For Life is a program that provides wraparound coverage for beneficiaries who are eligible for both TRICARE and Medicare. When a beneficiary enrolls in both Medicare and TRICARE, Medicare becomes their primary insurance, and TRICARE For Life works as a wraparound.