Formulary and Tiers: What are they?
Each and every Medicare Rx drug plan has what is called a “formulary,” which is a list of drugs that are covered by that prescription drug plan. Within each formulary there are classes of drugs. Under Medicare rules each of these formularies must contain at least two medications from each class or type of medication. Because there are many drugs within each type, every prescription drug plan can have a different list of Rx drugs that they cover.