Is it necessary for dually eligible clients to have both their Medicare and Medicaid coverage administered by the same insurance company?

No. If an individual has Medicare coverage through a Medicare Advantage plan and Medicaid coverage through a Medicaid managed care plan, it is possible but not required for the Medicare Advantage plan and the Medicaid managed care plan to be administered by the same insurance company. There may be potential benefits to such an arrangement, such as having to contact only one insurance company instead of two. However, they will still have to navigate two separate sets of coverage and benefits, as well as billing requirements. 

Note: This type of arrangement is not the same as enrolling in a single integrated care plan that is administered by one insurer, which provides a higher level of care coordination.