For Medicare-covered services, you must first pay the Medicare Part B annual deductible, which is $147 in 2013.

After you have met your deductible, you pay a Part B coinsurance for Medicare-covered services. For doctors’ visits you generally pay 20 percent of the Medicare-approved amount. For mental health services you pay 35 percent of the Medicare-approved amount.

You may have to pay more depending on what your doctor charges and whether the doctor takes Medicare assignment:

• Most doctors who treat patients with Medicare accept assignment, which means they agree to accept the Medicare-approved amount as payment in full. Participating providers always take assignment.

  When you see a doctor who takes assignment, you are only responsible for the coinsurance amount.

Non-participating doctors, or doctors who don’t routinely take assignment, can bill their Medicare patients up to 15 percent more than Medicare’s official amount for non-participating providers for most services and can request full payment up front for services.

• If you see a doctor who does not take assignment, you pay up to 15 percent of the Medicare’s official amount for providers who do not take assignment. This extra 15 percent is called the limiting charge. The beneficiary must pay the provider the normal coinsurance (usually 20 percent of the non-participating provider amount) plus the limiting charge if the provider chooses to impose it. These federal limiting charge laws don’t apply to certain providers, such as durable medical equipment suppliers. If these providers don’t accept assignment, they aren’t limited in how much they can charge.
• Some states may have stricter limits on what doctors may charge you. You can call your State Health Insurance Assistance Program (SHIP) to find out more.

Providers who have opted out of Medicare can charge their Medicare patients whatever they want. They must officially opt out. These providers do not submit any claims to Medicare and are not subject to the Medicare law that limits the amount providers may charge patients.

When you see a doctor who has opted out of Medicare, you pay the entire cost of your care (except in emergencies). The doctor should have you sign a private contract that states that you understand you are responsible for the full cost of the services. Medicare will not pay for any of the cost of services you receive.