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Medicare Part D — prescription drug coverage — is one of the most confusing parts of the Medicare system. There are dozens of plans available in any given county, with wildly different premiums, deductibles, formularies, and pharmacy networks. Two people in the same zip code can have very different "best plans" depending on which drugs they take.
The good news is that the selection process is straightforward once you know what to look at. Here is how to do it correctly.
Step 1: List Every Prescription Drug You Take
Start with a complete list of all your medications, including:
- Brand name and generic name
- Dosage (milligrams)
- How many you take per day and per month
This list is your single most important tool in choosing a Part D plan. Do not skip or approximate this step — the difference between a drug being on tier 1 (generic, lowest copay) and tier 4 (non-preferred brand) can mean hundreds of dollars per year in one plan vs. another.
Step 2: Check the Formulary
Every Part D plan has a formulary — a list of covered drugs organized into tiers. Tiers typically look like this in 2026:
| Tier | Drug Type | Typical Copay |
|---|---|---|
| 1 | Preferred generics | $0–$5 |
| 2 | Non-preferred generics | $10–$20 |
| 3 | Preferred brand-name | $40–$60 |
| 4 | Non-preferred brand-name | $90–$150+ |
| 5 | Specialty drugs | 25–33% coinsurance |
The same drug can be on completely different tiers across different plans. A medication that costs you $5/month on one plan could cost $95/month on another. This is why formulary comparison is non-negotiable.
How to check: Use the Medicare Plan Finder at medicare.gov and enter your medications. The tool calculates your estimated annual drug costs across all available plans in your area — it is the most reliable comparison tool available.
Step 3: Evaluate the Deductible
In 2026, the maximum Part D deductible is $590 per year. Some plans waive the deductible entirely; others apply it in full.
A plan with a $0 deductible but higher premiums may or may not save you money depending on your drug spend. Calculate total annual cost: premiums + deductible + copays for your specific drugs.
Step 4: Verify Your Pharmacy Is In-Network (and Preferred)
Part D plans negotiate different rates with different pharmacies. Most plans have a network of covered pharmacies and a smaller sub-network of preferred pharmacies where you pay lower copays.
If you use a specific pharmacy chain — say, Walgreens, CVS, Walmart, or a local independent — confirm it is in-network and ideally preferred under any plan you are considering.
Mail-order pharmacies are an important option to consider. Most Part D plans offer lower copays for 90-day supplies via mail order, which can generate meaningful savings for maintenance medications you take long-term.
Step 5: Look at the Star Ratings
CMS (the Centers for Medicare & Medicaid Services) rates Part D plans on a 1–5 star scale annually. The ratings reflect:
- Drug pricing and patient safety
- Member experience and customer service
- Formulary management
- Appeals and complaints history
A 4- or 5-star plan is generally better-managed and has fewer problems. In an otherwise close comparison between two plans, star rating is a reasonable tiebreaker.
Step 6: Run the Total Annual Cost Calculation
This is the key step most people skip. Do not just compare monthly premiums.
Annual total cost = (Monthly premium × 12) + Annual deductible + (Your estimated annual drug copays)
The Medicare Plan Finder does this calculation for you when you enter your medications. It shows you a side-by-side estimated annual drug cost for every available plan — making it much easier to identify the true lowest-cost option for your situation.
Common Mistakes to Avoid
Choosing based on premium alone. A $0 premium plan can cost more in total than a $30/month plan if your drugs have high copays on that formulary.
Not checking prior authorization requirements. Some plans require prior authorization (PA) before covering certain drugs. This means extra paperwork and sometimes delays getting your medication. Check if any of your drugs require PA before enrolling.
Ignoring quantity limits. Some plans cap how many pills per month they will cover. If your doctor prescribes a higher dose than the plan allows, you may face coverage gaps.
Forgetting to re-evaluate each year. Formularies change every year. A plan that was perfect in 2025 may have moved one of your drugs to a higher tier — or dropped it entirely — in 2026. Review your plan every October during the Annual Enrollment Period (AEP: October 15–December 7).
Extra Help (Low Income Subsidy): You May Qualify
If your income and assets are below certain limits, you may qualify for the Extra Help (also called Low Income Subsidy or LIS) program. In 2026, Extra Help can:
- Eliminate or dramatically reduce your Part D premium
- Reduce your deductible to $0
- Cap your copays as low as a few dollars per prescription
Eligibility is based on income and assets, not on health status. To check eligibility and apply, contact Social Security at 1-800-772-1213 or visit ssa.gov.
Choosing the right Part D plan for your specific drug list takes about 20 minutes with the right guidance. Schedule a free consultation and we will run the comparison together, including every available plan in your county.
Licensed in Florida, Alabama, Georgia, and North Carolina.
Frequently Asked Questions
Can I change my Part D plan outside of the Annual Enrollment Period? Generally no, unless you qualify for a Special Enrollment Period. Qualifying events include losing other drug coverage, moving to a new service area, or qualifying for Extra Help. Outside of these situations, AEP (October 15–December 7) is your annual window to change Part D plans.
What happens if I don't enroll in Part D when I'm first eligible? If you do not have other creditable drug coverage and delay enrolling in Part D, you will owe a late enrollment penalty equal to 1% of the national base premium per month of uncovered gap — permanently added to your premium.
Does Medicare Advantage include Part D? Most Medicare Advantage plans include Part D drug coverage built in (called MA-PD plans). If you enroll in Medicare Advantage with drug coverage, you do not need a separate Part D plan. If your Medicare Advantage plan does not include drug coverage, you cannot add a standalone Part D plan.
How often does a Part D formulary change? Formularies can change annually at each plan year (January 1). Mid-year changes are allowed under certain circumstances, but coverage of drugs you are currently taking must generally be maintained for the remainder of the plan year if you are already taking them.
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Max Zlobin
Founder & Independent Medicare Advisor
Max is a licensed independent insurance specialist dedicated to helping seniors navigate the complex world of Medicare. Based in Fort Walton Beach, Florida, he provides unbiased plan comparisons, personalized enrollment help, and ongoing coverage reviews.
