Medicare Prescription Drug Plans are available from private insurance companies contracted with Medicare to provide and coordinate prescription benefits to beneficiaries. As a Medicare beneficiary, there are two ways for you to get prescription drug coverage (Medicare Part D): through a stand-alone Medicare Prescription Drug Plan, if you have Original Medicare, or through a Medicare Advantage Prescription Drug plan. Because these plans are offered through Medicare-approved private insurance companies, this basically means that each Medicare Prescription Drug Plan will provide different types of prescription drug coverage. It's the insurance company that ultimately decides which drugs to cover under its prescription drug plan and at what benefit level.
 

The different levels of covered drugs under the Prescription Drug Plan are called "tiers." The tiers represent how much you pay out of pocket for the Part D drugs listed in each particular tier. For example, the plan may have one tier for generic drugs, another for brand-name drugs, and even a third tier for preventive drugs used to control certain medical conditions.
 

This list of covered prescription drugs is called a "formulary," and it contains all the drugs that the Medicare Prescription Drug Plan or Medicare Advantage Prescription Drug plan will cover. Keep in mind that formularies may change at any time; your Medicare plan will notify you if necessary. Generally, a plan covers drugs that cost less at a higher level, meaning you pay less out of pocket. Thus, it's always in your interest to ask your doctor to prescribe drugs that are on your Medicare Prescription Drug Plan's formulary. Usually, generic drugs are the least expensive.

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