Medicare Part D and Medicare Advantage plans that include drug coverage use a formulary—the plan’s list of covered drugs. If a medication is not on that list, or moves to a higher cost tier, you can pay far more than the plan’s advertised premium suggests. That matters every year, and especially before the Annual Enrollment Period (October 15–December 7), when most people choose drug coverage for the following year.
For calendar year 2026, Part D has an annual out-of-pocket cap on covered formulary drugs (often discussed as the $2,100 figure in federal materials). Spending on drugs the plan does not cover does not help you reach that cap—you pay full retail for non-covered medications.
Why premium alone misleads
- Tiers and cost-sharing change. A $0 premium plan can charge high copays for your specific drugs.
- Preferred pharmacies matter. Mail order, retail, and specialty pharmacies can have different prices under the same plan.
- Prior authorization and step therapy can delay or block access even when a drug is “on the list.”
- Combination products (two drugs in one pill, for example) may be listed differently than separate prescriptions.
Use Plan Finder with your real list
The official tool at Medicare.gov Plan Finder lets you enter each prescription (name, strength, how often you fill it) and your preferred pharmacies. It estimates total yearly drug cost, not just the plan premium. That is the comparison worth making in Idaho, Oregon, Texas, and Washington—counties and plan offerings differ, but the workflow is the same.
- Build a current medication list (include over-the-counter items only if your doctor prescribes them for coverage).
- Add your pharmacy or pharmacies.
- Compare a few plans side by side on estimated drug cost and note whether your drugs appear on each formulary.
- Read the plan’s Summary of Benefits and drug coverage rules for anything Plan Finder flags.
Stand-alone Part D vs Advantage with drugs
If you have Original Medicare plus a Medigap policy, you usually buy a separate Part D plan. If you are in Medicare Advantage, drug coverage may be bundled—still check the formulary for next year even if the plan name stays the same. Switching during Annual Enrollment can change both medical and drug benefits.
Want help running the numbers?
We can walk through Plan Finder with your medication list and compare options in your county at no cost to you.
This article is for general education. It is not a plan recommendation, quote, or guarantee of coverage. Benefits, premiums, networks, and eligibility vary by plan and county and can change. CDA Insurance LLC is an independent insurance agency and is not connected with the U.S. government or the federal Medicare program. Official program information is available at Medicare.gov or 1-800-MEDICARE.