With tens of billions of dollars in contracts at stake, a dozen health plans have told Florida officials they are challenging newly awarded Medicaid contracts.

The challenges could complicate plans by the state Agency for Health Care Administration to transition to new five-year contracts for Florida’s massive Medicaid program by Jan. 1. Medicaid is Florida’s safety-net health program that provides care for nearly 4 million poor, elderly and disabled people, with 85 percent of beneficiaries enrolled in managed-care plans.