Prescription drug plans, picked by what you actually take.

Part D is the part of Medicare that pays for prescription drugs. It sounds simple. It isn't. Each Part D plan has its own list of covered drugs (a formulary), its own copay tiers, its own preferred pharmacies, and its own deductible. Two plans with similar monthly premiums can cost you wildly different amounts depending on what you actually fill at the pharmacy.

How Part D actually works

When you fill a prescription, the pharmacy runs it through your Part D plan. Your plan looks up the drug in its formulary, finds the copay tier (typically Tier 1–5), and tells the pharmacy what you owe. Cheap generics are usually Tier 1 ($0–$5 copays); expensive specialty drugs can be Tier 4 or 5 (often 25–33% coinsurance, which on a $5,000/month drug means $1,250+ out of pocket every month).

The plan you pick matters most if you take expensive drugs. For someone on cheap generics, almost any plan works. For someone on insulin, a GLP-1, a biologic, or any specialty medication, the difference between the right plan and the wrong plan can be $3,000+ per year.

The structure of a Part D plan

Every Part D plan has four phases over a calendar year. You start at the deductible, then move through initial coverage, then catastrophic coverage. Here's what each one means in practice:

1. Deductible — you pay full negotiated price for drugs until you hit the plan's deductible (max $590 in 2026; many plans have $0 deductible on Tier 1 and 2)
2. Initial coverage — you pay your tier-based copays
3. Catastrophic coverage — once your total drug costs hit the new annual out-of-pocket cap ($2,100 in 2026), the plan pays 100% for the rest of the year

Different plans put different drugs on different tiers, so the same prescription can be a $5 copay on one plan and a $90 copay on another. There is no shortcut to finding the right plan — you have to run your specific drug list against every plan in your zip code.

How we approach Part D selection

On a Part D review call, we'll walk through your medication list one drug at a time. For each one, we'll check:

• Whether the drug is on the plan's formulary at all (some specialty drugs are excluded by some plans)
• What tier it's on, and what the copay is
• Whether the plan has prior authorization or step therapy requirements that could delay your fill
• Which pharmacies are "preferred" — preferred pharmacies usually have meaningfully lower copays than standard pharmacies
• Whether mail-order would save more money

Then we compare the top 3 plans on total annual cost — premium + deductible + expected copays — across all your drugs. The cheapest premium is almost never the cheapest plan overall.

The annual review nobody does (but should)

Here's the part most seniors miss: Part D plans change every year. Formularies get updated, tier placements change, premiums rise, and your medication list probably evolves too. The plan that was perfect for you in 2025 might be the most expensive plan for you in 2026.

Every year during Annual Enrollment (October 15 – December 7), we review every Part D client's plan against the new year's plans and re-recommend if there's a better fit. About a third of the time, switching saves real money. About 10% of the time, switching saves over $1,000 a year. There is no fee for this review.

When you can enroll or switch

• Initial Enrollment Period — the 7 months around your 65th birthday
• Annual Enrollment Period (AEP) — October 15 through December 7, for the following calendar year
• Special Enrollment Periods — moving, losing employer coverage, qualifying for Extra Help, and a few others

If you miss your Initial Enrollment Period and don't have other "creditable" drug coverage, you'll owe a Late Enrollment Penalty — a permanent 1% of the national base premium per month you went without coverage, added to your premium forever. Try our penalty calculator to see what this would cost you.

Frequently asked questions