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.

Changes in a Part D formulary

Each Medicare Prescription Drug Plan is required to publish its formulary on the plan’s website. The plan must also tell you when it removes drugs from the Part D formulary. The formulary may change at any time. You will receive notice from your plan when necessary.

Medicare Prescription Drug Plans are restricted from making changes to the listed drugs — or changing the tiered pricing — between the beginning of the plan’s annual election period until 60 days after the plan coverage begins. The exception to this is if the FDA determines a drug is unsafe or a manufacturer removes a drug from the market.

Mid-year changes to formulary drugs are limited, and your plan must always notify you of such changes. The notification of change must include the name of the drugs, Part D change type (e.g., add/remove/tier change), the reason for the change, alternate drugs, new Part D cost sharing, and exceptions.

Drugs covered under Medicare Part D

Medicare Prescription Drug Plans and Medicare Advantage Prescription Drug plans cover all commercially available vaccine drugs when medically necessary to prevent illness. Otherwise, the plan decides which drugs to cover, which drugs not to cover, and under which tier to cover them.

Before enrolling in a Medicare Prescription Drug Plan or Medicare Advantage plan that includes drug coverage, you should review the plan’s formulary to see which drugs it covers.

Drugs not covered under Medicare Part D

Since each Medicare Part D Prescription D plan decides which drugs not to cover on its formulary, the list here is not complete. However, plans usually do not cover:

  • Weight loss or weight gain drugs
  • Drugs for cosmetic purposes or hair growth
  • Fertility drugs
  • Drugs for sexual or erectile dysfunction
  • Over-the-counter drugs

Medicare Part D also does not cover any drugs that are covered under Medicare Part A or Part B.

Your Medicare Part D rights

If you have a Medicare Prescription Drug Plan or Medicare Advantage Prescription Drug plan, you have the right to:

  • Receive “coverage determination” — a written explanation from your plan about your benefits, including how drugs are covered, your costs for drugs, any coverage requirements (such as drugs that require the plan’s prior authorization, and requirements for making coverage exceptions.
  • Ask for exceptions to drugs not covered by your plan’s formulary.
  • Ask for exceptions to waive plan coverage rules (like prior authorization).
  • Ask for a lower copayment for higher-cost drugs if you or your prescriber believe you cannot take any of the lower-cost drugs for the same condition.