When a doctor doesn't take Medicare: assignment, opt-out and second opinions

With Original Medicare, what you pay depends a lot on which of three kinds of provider you see.

1. Providers who accept assignment

They accept the Medicare-approved amount as full payment for covered services. You pay only your deductible and coinsurance, usually 20%. This is the cheapest choice.

2. Non-participating providers

They take Medicare patients but decide case by case whether to accept assignment. When they don't, they can generally charge up to 15% more than the Medicare-approved amount (the "limiting charge"), and you may have to pay the full amount at the visit. They still have to send the claim to Medicare; if they refuse, you can file it yourself. Medigap Plans F and G pay these extra charges; Plan N doesn't.

3. Providers who opted out

Some doctors leave Medicare entirely, for at least 2 years at a time. To treat you, they ask you to sign a private contract and pay them directly, with no limit on what they charge. Medicare pays nothing for that care, except in emergencies, and because Medigap pays only after Medicare, it usually won't pay either. You can still see other doctors who take Medicare.

How to check before your visit

• Ask the office: "Do you accept Medicare assignment?"
• Look the provider up on Medicare.gov's Care Compare.
• In a Medicare Advantage plan, the rules are different: check that the provider is in the plan's network. See plan types.

Second opinions

Part B covers a second opinion before medically necessary surgery that isn't an emergency, and a third opinion if the first two disagree. You pay 20% of the Medicare-approved amount after the deductible. If the second doctor orders tests, Medicare covers them like other medically necessary tests.