When you're dual eligible, Medicare pays first, and Medicaid pays second. Medicaid never pays first for services covered by Medicare. Medicaid will only pay after either Medicare, employer group health plans, and/or Medicare Supplement (Medigap) Insurance plans have paid.
For example, services such as primary care visits, skilled nursing facility care, home care, and more are eligible for both Medicare and Medicaid coverage. In these scenarios, the service will first be covered by Medicare while Medicaid covers final payments such as copays or coinsurances.