How to Choose a Part D Drug Plan

Start with your drug list, not the premium

Two plans in the same ZIP code can differ by thousands of dollars a year for the same person. The difference is almost never the premium — it is which tier each plan assigns your medications to, & whether your drugs require prior authorization or step therapy.

• Write down every medication with exact strength & monthly quantity.
• Check each drug against the plan's formulary for the coming year, not the current one.
• Note the tier: generics on tiers 1–2 are cheap; brand & specialty tiers are where costs explode.
• Look for restrictions: prior authorization, quantity limits & step therapy.

Pharmacy networks matter more than people expect

Most plans have preferred & standard pharmacies. Filling the same prescription at a standard pharmacy instead of a preferred one can double your copay. Mail order is often the cheapest option for maintenance medications.

How Part D payment stages work now

• Deductible stage — you pay full negotiated cost until the plan deductible is met, if the plan has one.
• Initial coverage — you pay copays or coinsurance while the plan pays the rest.
• Catastrophic coverage — once your out-of-pocket spending reaches the annual cap, you pay $0 for covered Part D drugs for the remainder of the year.
• Everything resets each January 1.

Common mistakes

• Choosing the lowest premium & discovering a brand drug sits on a specialty tier.
• Skipping Part D entirely while healthy, then paying a permanent late-enrollment penalty.
• Not re-shopping during AEP — formularies change every single year.
• Assuming a manufacturer coupon works with Medicare. It doesn't; those are for commercial insurance only.