The GOP plan to overhaul Medicaid as part of the Affordable Care Act replacement could affect more than 11 million beneficiaries who are also covered by Medicare.

The population, commonly known as dual-eligibles, make up about 15% of the entire Medicaid population but account for 36% of Medicaid spending. Most dual-eligibles are 65 years or older but more than 4 million are younger adults living with severe disabilities.

Nearly all services currently paid for by Medicaid, including medical and long-term care, would all be paid under the fixed allotment proposed by the American Health Care Act, which is coming up for a House floor vote this week. The bill proposes changing Medicaid from an entitlement program with no limit on federal spending to one that places a per capita cap on federal funding.

That change would reduce federal Medicaid spending by $880 billion over the next 10 years, according to an analysis of the bill by the nonpartisan Congressional Budget Office.

Experts believe many states will make up for the loss in funds by cutting back benefits or eligibility.

And according to a report released Monday by the Kaiser Family Foundation, services Medicaid pays for when Medicare doesn’t, such as long-term support services could be on the chopping block.

Under the AHCA, once the cost of services exceeded the fixed amount allotted, the patient would incur costs.

Federal and state Medicaid spending on low-income Medicare beneficiaries totaled more than $146 billion in 2011, of which, 62% went to cover the cost of long-term care.

A reduction in federal Medicaid dollars could make states reduce payments to providers, drawing more away from the program. States often reimburse at a lower rate for dual-eligible patients since they are only required to pay at an amount covered by Medicaid, which pays at a lower rate than Medicare.

The effect for any given state would also vary with the growth in average health care and long-term care costs per person, the report concluded.