Donald Trump’s proposed health care policies have been largely vague, but the few specifics he has offered have led at least one expert to conclude that millions would lose coverage if the bombastic billionaire got his way as president.

The study from the nonpartisan Center for Health and Economy found that 18 million would lose coverage, and premiums in the individual insurance market would likely decline as well.

Much of the loss in coverage would come from Trump’s plan to turn Medicaid into a block grant program, which would likely deal a big blow to the millions who have gained Medicaid coverage as part of the Affordable Care Act’s expansion of the low-income health insurance program.