Most people think about their Medicare Advantage or Part D plan in terms of the premium, and stop there. But the piece that actually determines what you pay at the pharmacy counter — the plan’s drug formulary — changes every single year, sometimes significantly, whether or not you ever hear about it. AEP 2026 runs from October 15 through December 7, and it’s your one yearly window to fix a formulary problem before it costs you money in Plan Year 2027. Here’s how to review your Part D coverage properly before that window closes.
Why Your Drug Coverage Needs a Fresh Look Every Year
A formulary is simply the list of prescription drugs a plan covers, organized into cost tiers — generic drugs are usually the cheapest tier, and brand-name or specialty drugs cost more. Plans are allowed to revise their formularies annually: a drug that was Tier 2 this year can move to Tier 4 next year, or drop off the list entirely. None of that requires your plan to ask your permission first.
This is exactly why “my plan has always covered this” is not a safe assumption heading into a new plan year. If you take the same medications year after year without checking, you can end up paying substantially more starting January 1 simply because the plan changed, not because anything about your health did. For a broader look at what else can shift heading into a new plan year, our AEP 2026 guide covers the full picture beyond just drug coverage.
Start With Your Own Medication List
Before you look at any plan documents, write down every prescription you currently take, including the exact dosage and how often you fill it. This sounds basic, but it’s the step people skip, and it’s the one that makes everything after it faster and more accurate.
Once you have that list, compare it against your plan’s ANOC letter, which plans are required to mail by September 30 explaining what’s changing for Plan Year 2027. The formulary section is often the one that catches people off guard, since a medication can move to a higher cost tier or lose coverage entirely even when the rest of the plan looks unchanged. If your ANOC flags a change to a drug on your list, that’s your signal to look at alternatives before AEP 2026 ends. Our AEP 2026 prep checklist walks through building this kind of list step by step if you haven’t started yet.
Check the Pharmacy Network, Not Just the Drug List
A formulary tells you what’s covered. It doesn’t tell you where you can fill it at that price. Part D and Medicare Advantage plans work with specific pharmacy networks, and many offer a “preferred” tier of pharmacies where your copay is lower than at an out-of-network or non-preferred pharmacy for the exact same drug.
If you use a smaller local pharmacy or a mail-order service, confirm it’s still in your plan’s preferred network for 2027, since pharmacy contracts can change independently of the formulary itself. This matters even more if you’ve moved, since a plan’s network can look completely different depending on your ZIP code. It’s a detail that’s easy to overlook when you’re focused only on which drugs are covered, but it can meaningfully change what you pay out of pocket.
Know the Numbers That Protect You in 2026
A few Part D costs are set at the federal level and apply no matter which plan you choose, which makes them a useful baseline when you’re comparing options. In 2026, Part D has a $2,100 annual out-of-pocket cap on covered prescription drugs — once you or your plan has spent that much on your covered drugs in a calendar year, you pay nothing more for them through December 31. We break down exactly how that cap works, including how spending counts toward it, in our Part D $2,100 cap guide.
Insulin is covered separately: the cost cap for a month’s supply of covered insulin is $35, and it applies across every Part D and Medicare Advantage plan with drug coverage, regardless of which deductible stage you’re in. And if your income and savings are limited, Extra Help can lower your premiums, deductibles, and copays further — it’s a federal program administered through Social Security, and the income thresholds are often higher than people assume, so it’s worth checking even if you’re not sure you’d qualify. For the fuller set of 2026 Medicare costs, including how Part D costs relate to Part A and Part B, see our Medicare costs guide. Unfamiliar terms like formulary, tier, or Extra Help are also defined in our Medicare glossary.
What to Do If Your Coverage No Longer Fits
If your review turns up a real problem — a maintenance medication moved to a high-cost tier, your pharmacy dropped out of network, or your plan’s formulary shrank in a way that affects you — AEP 2026 is your chance to fix it before it takes effect. You can switch Part D plans, switch Medicare Advantage plans, or move between Medicare Advantage and Original Medicare during this window, and the change takes effect January 1 of Plan Year 2027.
If nothing changed and your current plan still covers everything you take at a price you’re comfortable with, you don’t have to do anything — your coverage continues automatically. The goal of this review isn’t to make you switch plans out of habit. It’s to make sure that if you stay, you’re staying because you checked, not because you assumed.
Reviewing a formulary against your own medication list takes less than an hour for most people, and it’s the single most useful thing you can do before AEP 2026 opens if you take regular prescriptions. Medicare.gov’s Plan Finder lets you check a plan’s 2027 formulary directly once it’s published, drug by drug. If your medication list is long or complicated and you’d rather not sort through it alone, that’s a reasonable thing to get help with too.
Have questions? Kayla Price is a licensed insurance agent serving NC, SC, GA, FL, VA, MD, MI, KS, TX, and OH. Call (866) 648-1578 or visit priceservicesgroup.com.