Problems may crop up if you have special healthcare needs.

Medicare enrollees are moving in greater numbers than ever to the program’s managed care option as a way to save money. But the tradeoff is much less ability to use their preferred doctors and hospitals.

Seniors can choose between traditional fee-for-service Medicare – which is accepted by most healthcare providers – or a Medicare Advantage plan. The latter encompasses health maintenance organizations (HMOs) or preferred provider organizations (PPOs), which control costs by creating healthcare provider networks that enrollees must use.