There are four types of costs associated with Medicare Part D prescription drug coverage: premiums, deductibles, copayments, and a coverage gap during which period you must pay the full cost of your medications. People with low incomes may apply for a subsidy from the Social Security Administration to reduce these costs.
In 2010, Part D premiums range from $0-$50 per month (depending on the plans available in your town and on the partiular plan you choose). The deductible -- the amount you must pay out-of-pocket before Medicare will contribute to your prescription costs -- for most plans in 2010 is $310. After you meet the deductible, Medicare will pay roughly 75% of your prescription costs. However, after you and your plan together pay a certain amount for covered prescription drugs ($2,830 in 2010), your plan stops paying anything and you must pay the full cost of the prescription. The plan begins to pay again -- and pays 95% of all further costs -- when total expenditures reach a "catastrophic" level ($4,550 in 2010).