Every Medicare Part D prescription drug plan (PDP) will have a different formulary (drug list). Within a formulary, many Part D plans will sort drugs into cost-sharing “tiers.” Typically, plans have 4 or 5 tiers (or levels) and each tier includes different medications. Your plan will determine what your copayment or cost-share is for each tier. Every plan is different. A drug in a lower tier will cost less than a drug in a higher tier. Often, generic medications will fall into tiers 1 and 2. Brand-name and specialty medications will be in higher tiers. Your doctor may ask for a “tiering” exception if your drug is on a higher tier and cannot be substituted with a similar drug on a lower tier.