Ominous warnings about Medicare Advantage plans have sounded for more than a year now.

Carriers say federal funding cuts to these privately run versions of Medicare will force them to whack plan benefits, hike premiums or leave some geographic markets entirely as they continue to fight rising health care costs. The government is paring back the money it provides for this coverage as part of its effort to fund the health care overhaul, which aims to cover millions of uninsured people.

Plan changes are starting to crystallize for Medicare Advantage customers who are about a month into the annual open enrollment window in which they can search for new coverage. Benefits experts say patients are seeing fewer plan choices this year, and more are losing doctors from their insurance coverage networks. Open enrollment lasts until Dec. 7, and many customers wait until the final weeks to pick a plan.