En español | Like most other kinds of insurance, Medicare has a variety of premiums, deductibles and copays that are required for coverage. (But you may be able to get help with the costs if your income is limited — see next section, "Help Paying Out-of-Pocket Expenses.")

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Premiums: There's no premium for Part A if you paid enough in Medicare taxes while working. Part B requires a monthly premium — at the standard rate of $104.90 a month in 2013. Part D drug plans charge additional premiums, and so do most Medicare Advantage plans.

You pay higher premiums for Parts B and D if your modified adjusted gross income on your latest tax return is above $85,000 if you're single, or $170,000 if you're married and filing joint returns. (For details see "Medicare Premiums: Rules for Higher-Income Beneficiaries.")

Deductibles: You pay annual deductibles for Part B ($147 in 2013) and Part D (up to $325 in 2013) before coverage kicks in. Part A has a deductible ($1,184 in 2013) for hospital stays. Some Part D and Medicare Advantage plans reduce or waive deductibles.

Copays: In traditional Medicare (Parts A and B), you pay 20 percent of the Medicare-approved amounts for most Part B services. In Part A, after meeting the deductible you pay nothing more for up to 60 days in the hospital in any one benefit period, but additional days may require daily copays. In Part D and Medicare Advantage plans, you pay the copays required by your plan.

Part D drug coverage is uniquely designed. Depending on the cost of the drugs you use, you may move through four different phases of coverage during each calendar year:

• Annual deductible: This is an amount you may pay out of pocket for your drugs before coverage kicks in. Many Part D plans charge no deductible or less than the maximum amount set by law — $325 in 2013.
  
  
• Initial coverage period: You pay the copays required under your plan until the total cost of your drugs — what you've paid and what your plan has paid — reaches a certain amount ($2,970 in 2013) from the beginning of the year or, if you joined the program partway through the year, from when your coverage began.
  
  
• Coverage gap (aka "the doughnut hole"): Once your drug costs exceed the initial coverage limit above, you're in the doughnut hole. Your plan then pays nothing, unless it provides some coverage in the gap. In 2013, you get an approximately 52.5 percent discount on brand-name drugs in the gap from the manufacturers and a 21 percent discount on generic drugs from the government. (These discounts were established under the new health care law, which will also gradually reduce your costs every year until by 2020 you'll pay no more than 25 percent of the price of any drug in the gap.)
  
  
• Catastrophic coverage: If the full cost of your drugs in the gap, plus what you've paid out on deductibles and copays before hitting the gap, reach a certain limit ($4,750 in 2013), coverage resumes. You then pay no more than 5 percent of the cost of any drug until the end of the year.
  
  

This cycle of phases — deductible, initial coverage, doughnut hole and catastrophic coverage — repeats itself every calendar year. So if you are in the doughnut hole at the end of December, full coverage begins again Jan. 1 or, if your plan has an annual deductible, as soon as you've met it. If your drug costs are not high, you may not reach the doughnut hole at all.

For detailed information on how the Medicare prescription drug program works, see the AARP Bulletin's consumer guide "Medicare Part D & You."

Next: How to get help paying out-of-pocket expenses. »