Medicare Part D Plan Comparison: How to Find the Best Drug Plan for Your Parent

Why Sorting by Lowest Premium Gets It Wrong

The cheapest Part D plan in your parent's ZIP code might cost them thousands more than a plan with a higher monthly premium. That's because premiums are only one piece of the total annual cost. A $12/month plan with your parent's blood thinner on Tier 4 at 40% coinsurance will cost far more than a $45/month plan that covers the same drug on Tier 2 with a $15 copay.

The number that matters: Total Annual Drug Cost + Premium. That's 12 months of premiums plus the plan's projected cost-sharing for your parent's specific medications at their specific pharmacy.

The 7-Step Comparison Process

1. Build Your Parent's Drug List

Pull every prescription bottle from the medicine cabinet. Write down the exact drug name, strength, formulation (tablet, capsule, liquid, patch), and the quantity filled per month. Skip over-the-counter medications, vitamins, and supplements — Part D doesn't cover those.

2. Run the Medicare Plan Finder

Go to Medicare.gov, enter your parent's ZIP code, and input each drug. When the system suggests a generic equivalent, take it unless the doctor has written "Dispense as Written" for medical reasons.

Save the Drug List ID and Password Date the tool generates. You'll need these to pull the list back up without re-entering everything.

3. Set the Right Pharmacy

Select your parent's actual pharmacy — not the default. Then add at least one alternative local pharmacy. The Plan Finder calculates costs based on each plan's pharmacy network contracts, and preferred pharmacies can save an average of $129 per year over standard network pharmacies.

4. Sort by Total Annual Cost

The Plan Finder's default sort often prioritizes premiums. Switch to sorting by estimated total annual drug cost (premiums + cost-sharing). This single change will surface plans that actually cost less over the year.

5. Check Formulary Restrictions

For each promising plan, look for restriction flags on your parent's medications:

• PA (Prior Authorization): The plan requires proof of medical necessity before covering the drug. Someone will need to coordinate with the prescribing doctor.
• ST (Step Therapy): The plan forces your parent to try cheaper alternatives first and fail before covering the prescribed medication.
• QL (Quantity Limits): The plan caps how many doses are covered per month.

A plan with the lowest total cost but prior authorization on your parent's daily heart medication is risky if the doctor's office is slow with paperwork.

6. Check Star Ratings

Plans rated 4 stars or above have demonstrated strong customer service, timely appeals processing, and accurate drug pricing. Below 3 stars signals recurring operational problems that will create headaches when you need the plan to work.

7. Compare Standalone PDP vs. Medicare Advantage

A standalone Prescription Drug Plan (PDP) pairs with Original Medicare. A Medigap supplement is separate and optional. A Medicare Advantage plan with drug coverage (MA-PD) bundles medical and drug coverage under one insurer with a network of providers.

The right choice depends on your parent's doctors. If their specialists are out-of-network on MA-PD plans in the area, a standalone PDP preserves provider flexibility. If they're healthy enough that the MA-PD network covers their care, bundling can simplify administration.

What Changes in 2026

The 2026 plan year carries several structural shifts worth knowing before you compare:

• $2,100 annual out-of-pocket cap: Once your parent's True Out-of-Pocket costs hit this number, all covered drugs cost $0 for the rest of the year.
• No more donut hole: The coverage gap is permanently eliminated. Your parent moves directly from the initial coverage phase to catastrophic coverage.
• $615 standard deductible: Up from $590 in 2025. Individual plans may waive or reduce this.
• Premium stabilization winding down: The federal demo that held premiums artificially low is phasing out, with the final year in 2026. Expect bigger premium jumps for 2027.

One Comparison Is Not Enough

The plan that won last year's comparison might lose this year's. Formularies change annually — a drug on Tier 2 this year can move to Tier 3 next year. Pharmacy network contracts get renegotiated. Every September, your parent's plan sends an Annual Notice of Change (ANOC) listing what's different for the coming year. That's your cue to run the comparison again during open enrollment (October 15 through December 7).

Our Medicare Part D guide includes a pre-filled comparison worksheet that tracks total annual cost across plans, so you can run the evaluation without juggling browser tabs.

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