With Original Medicare, a primary care doctor is not required. You can visit any doctor who accepts Medicare.
With a Medicare Advantage plan, your choice of doctor depends on whether you select a health maintenance organization (HMO) or preferred provider organization (PPO) plan.
With an HMO plan, you can choose your primary care physician from any doctor in the plan's network. If you opt for a PPO plan, generally, choosing a primary care physician is optional. With both types of plans, you'll usually save money by visiting a network provider.
It's important to note that Medicare Advantage plans must offer emergency coverage outside of the plan's service area, anywhere in the U.S.