The method

Choosing a Part D plan: ignore the premium, sort by total annual cost

Short answer: list your exact drugs and doses, enter them in Medicare’s official Plan Finder with your preferred pharmacy, and sort the results by total annual cost, never by premium. That’s the whole method. The premium is one input among four (premium, deductible, your drugs’ copays, pharmacy status), and the plan with the lowest premium is frequently among the most expensive for your actual prescriptions. Here’s the walkthrough plus the traps.

By the Medicare Decoder team · Updated August 10, 2026 · 4-minute read · Figures are official 2026 amounts

Key takeaways

Sort by total annual cost (premiums plus your drugs’ projected costs), the number Plan Finder computes for you.
The lowest-premium plan is often the wrong plan: formularies and tiers differ wildly for identical drugs.
Check your specific pharmacy’s status; “preferred” vs. “standard” at the same chain changes prices meaningfully.
The 2026 guardrails apply everywhere: deductible capped at $615, out-of-pocket capped at $2,100, insulin at $35/month.
Taking nothing? Buy the cheapest plan anyway as penalty insurance; the late fee is 1% of $38.99 per month, permanent.

Jump to The 20-minute method The four traps If you take no drugs After you choose FAQ

The 20-minute method, step by step

Minutes 0–5: build the drug list. Exact names, doses, quantities per month, from the bottles, not memory. Note which are generics and which brand-only.
Minutes 5–10: enter it once at medicare.gov/plan-compare. Add your zip code and your actual pharmacy (plus one backup). The tool saves the list to reuse every fall.
Minutes 10–15: sort by "lowest drug + premium cost." This is the entire trick. The tool projects your full year (premiums + deductible + copays through the phases) per plan. Read the top three.
Minutes 15–20: verify the top pick’s details. Every drug on formulary? Any prior authorization or step therapy flags on drugs you take today? Your pharmacy listed as preferred, not merely in-network? Then enroll through the tool; the new plan auto-cancels the old each January 1.

The four traps that survive the method

Trap	What it looks like	The defense
Premium hypnosis	"$0 premium plan!" with your brand drug on tier 4	Sort by total annual cost, always
Pharmacy mismatch	Great plan pricing, at a pharmacy across town	Enter YOUR pharmacy; check preferred status specifically
Mid-year drug changes	Plan chosen for drugs you quit in March	Re-run the tool each fall with the current bottle list
Restriction blindness	Formulary says yes; prior-auth flag says "yes, eventually"	Open the plan’s detail view and read the PA/step-therapy flags on your drugs

Plan Finder projections assume the drug list you enter; the tool is only as current as your list.

The guardrails that travel with every plan in 2026: deductibles can’t exceed $615, your covered-drug out-of-pocket stops at $2,100, insulin is capped at $35/month, and the Prescription Payment Plan can smooth costs monthly. Weight-loss GLP-1s run through the separate Bridge program, outside Part D entirely, so don’t judge a plan by drugs the Bridge handles.

If you take no medications

Buy the cheapest plan in your zip code anyway. It’s penalty insurance: skipping creditable coverage accrues a permanent late fee of 1% of the national base premium ($38.99 in 2026) per month, and, more practically, the year a prescription arrives mid-year you’ll want a formulary and the $2,100 cap already in place rather than waiting for the next enrollment window. A minimal-premium plan is the cost of keeping the door open.

After you choose: the two-calendar habit

September: read the Annual Notice of Change, where next year’s premium, deductible, and your drugs’ tier moves are disclosed in tables. October 15–December 7: re-run this exact method with the current bottle list, because plans reprice annually and loyalty is billed, not rewarded. The people who run this 20-minute loop every fall routinely save hundreds a year over the people who chose once in 2026 and coasted. Your drug list from step one, kept current, is the whole maintenance system.

Questions people also ask

How do I choose the best Part D plan for me?

Enter your exact drugs, doses, and pharmacy at Medicare’s official Plan Finder and sort by total annual cost (premium plus projected drug costs). Verify the winner covers every drug without prior-authorization surprises and lists your pharmacy as preferred, then enroll through the tool.

Why is the cheapest premium Part D plan not the best?

Because formularies and tier placements differ per plan: a $0-premium plan can put your specific drug on an expensive tier or off formulary entirely, costing far more annually than a $40-premium plan that covers it well. Total annual cost is the only fair comparison.

Should I get Part D if I don’t take any medications?

Yes, the cheapest plan available, as penalty insurance. Going without creditable coverage adds a permanent 1%-per-month penalty (of the $38.99 national base premium), and enrolling mid-year after a new diagnosis usually isn’t possible until the next window.

What are the Part D costs caps for 2026?

Deductibles are capped at $615, annual out-of-pocket spending on covered drugs stops at $2,100, insulin is capped at $35 a month, and every plan must offer the Medicare Prescription Payment Plan to spread costs into equal monthly payments.

Can I switch Part D plans every year?

Yes, during Annual Enrollment (October 15–December 7) with the new plan starting January 1 and replacing the old automatically. Re-running the Plan Finder each fall with your current drug list is the single highest-return 20 minutes in Medicare.

Sources for this article

Medicare.govMedicare Plan Finder: the official tool this method runs on.
Medicare.govDrug coverage costs: the deductible cap, $2,100 cap, and penalty formula.
CMS.gov2026 premiums and deductibles: the year’s baseline figures.

Figures checked against these sources in August 2026. We update within weeks when CMS publishes new amounts.

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