How to choose a Part D plan

Start with your drugs

Choosing a drug plan well begins with one thing: an accurate list of the medications you take, with doses. Every Part D plan has a formulary — its list of covered drugs, sorted into pricing tiers — and the same medication can sit on different tiers in different plans. So the first question for any plan is simply whether it covers your specific drugs, and on what tier. A low-premium plan that doesn’t cover your medications isn’t a bargain.

Compare total cost, not premium

This is where most people go wrong. The premium is only one piece; what matters is your total cost for the year — premium plus deductible plus the copays or coinsurance for your particular drugs. Medicare’s Plan Finder at Medicare.gov does this math for you: enter your medications and it estimates each plan’s full annual cost. In 2026, a $2,100 cap on out-of-pocket drug spending limits the worst case, and you can spread those costs across the year through the Medicare Prescription Payment Plan if you choose.

Check pharmacies and restrictions

Two details can change the picture. First, pharmacy network: many plans have preferred pharmacies where your costs are lower, so check that your pharmacy qualifies, or consider mail order. Second, look for restrictions on your drugs — prior authorization, step therapy, or quantity limits — since these can affect whether and how easily you can fill them. A quick check now avoids surprises at the counter.

Review it every year

A Part D plan is not a set-and-forget decision. Formularies, tiers, premiums, and pharmacy networks all change each January, and so do your own prescriptions. During the Annual Enrollment Period each fall, it’s worth re-running your drug list through the Plan Finder — the plan that was cheapest last year may not be this year. A few minutes annually can save real money.