What is Medicare Part B?

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Part B is the medical insurance component of Medicare. It covers your costs to find and treat health problems before they become more serious. Medicare itself provides the coverage for original Part B and also for Part A, hospital insurance. The federal government enrolls many people in original Medicare automatically. Although Part A is free for most people, you must pay for Part B even if you're enrolled by the government.

Who Qualifies

Everyone receiving Social Security or railroad retirement benefits is automatically enrolled in Parts A and B at age 65. Everyone else who qualifies for free Part A can buy Part B, including those who are still working past age 65, many disabled people, and patients with end-stage kidney disease. Those who don't qualify for free Part A can buy Part B if they're U.S. citizens or have been living in the country legally for five years or more. People who qualify for A and B can bypass original Medicare for Medicare Advantage plans. These plans vary, but must offer at least as much Part B coverage as original Medicare.

Benefits of Part B

In general, Part B covers diagnostic and preventive services and everything that's medically necessary to diagnose and treat an illness or medical condition. For example, it covers annual wellness check-ups, flu shots, glaucoma tests, mammograms and bone mass screenings. It also pays for ambulance services, durable equipment such as crutches, inpatient and outpatient mental health care and second opinions. Some outpatient drugs, such as infused drugs, vaccinations and clotting factors, also fall under B.

What Medicare Doesn't Cover

Neither original Medicare Part B nor Part A covers long-term care, cosmetic surgery, acupuncture, foot care or cosmetic surgery. Routine dental care, eye exams for corrective lenses, hearing exams and hearing aids are also excluded. Some Medicare Advantage plans cover these additional products and services, but every plan is different. Part B Medicare coverage isn't the same from state to state or even within a state. In addition, the companies that process Medicare claims actually determine whether a treatment is medically necessary and whether or not it's covered.

Part B Costs

Costs for Medicare Advantage plans vary, but as of 2015, most people paid a monthly premium of $104.90 for Part B. Taxpayers filing individually or married and filing separately paid more if they earned an adjusted gross income over $85,000 per year. Those filing jointly pay more with annual earnings over $170,000. The premium is $146.90 per month after this second tier, and there are three additional tiers for higher earners. Everyone with Part B coverage must pay a $147 annual deductible. After meeting the deductible, you must pay a coinsurance percentage for most services -- for example, 20 percent of the cost.