Networks and prior authorization: what changes when you choose Medicare Advantage

How HMO and PPO networks work in Medicare Advantage, what prior authorization means in practice, and how to check before you enroll.

The two features that most separate Medicare Advantage from Original Medicare are networks and prior authorization. Neither is good or bad on its own, but both should be checked before you enroll.

Networks

• HMO plans usually require you to use in-network providers (except emergencies) and often need referrals for specialists.
• PPO plans let you go out of network at higher cost.
• Networks can change during the year, and doctors can leave.

Original Medicare has no network: any provider that accepts Medicare. With Medigap, your share is the same anywhere.

Prior authorization

Medicare Advantage plans can require approval before covering certain services: hospital admissions, skilled nursing, home health, advanced imaging, some drugs. Original Medicare rarely requires prior authorization. Federal rules adopted in recent years require MA plans to follow Original Medicare coverage criteria and limit some uses of prior authorization, but approvals and denials still happen.

Before you enroll, check

1. Are my primary care doctor, specialists and preferred hospital in network?
2. Does the plan require referrals?
3. What services need prior authorization?
4. What happens if I need care while travelling?
5. What is the in-network out-of-pocket maximum?

If a service is denied

You can appeal. The plan must explain the denial and how to appeal; many denials are overturned on appeal. Your State Health Insurance Assistance Program can help for free.

For the cost side of the decision, see Medigap vs Medicare Advantage and why the 20% matters.

Questions people ask

Does Original Medicare have a network?

No. Any provider that accepts Medicare can treat you.

What is prior authorization?

Approval a plan requires before it will cover a service.

Can a Medicare Advantage network change mid-year?

Yes, providers can leave networks during the year.

Can I appeal a denial?

Yes. Plans must provide appeal rights, and many denials are overturned.

Independent educational site. Not affiliated with or endorsed by the U.S. government, the federal Medicare program, or any insurance company. Figures are 2026 amounts published by CMS unless noted; check Medicare.gov for your situation.