Medicare Part D Open Enrollment: Check Your Drug Plan’s Formulary Before December 7

ByWalt Pearson

Medicare Part D open enrollment runs from October 15 to December 7, and it is the time to make sure your drug plan will still cover your medicines next year. The list of drugs a plan covers is called a formulary, and it can change every year, so a ten-minute check now can save you a surprise at the pharmacy in January.

This guide is based on Medicare.gov and Medicare’s official drug coverage guide, as checked on November 13, 2026. It is general information, not advice for your situation.

What a Medicare Part D Formulary Is

A formulary is simply a plan’s list of covered drugs. Medicare.gov explains that every Medicare drug plan has its own list, so there is no single list that fits all plans. A plan’s list can include both brand-name and generic drugs.

Plans sort the drugs on their list into groups called tiers. A drug in a lower tier generally costs you less than a drug in a higher tier. Medicare gives this example, and notes your plan’s tiers may be different:

  • Tier 1: lowest copayment, most generic drugs.
  • Tier 2: medium copayment, preferred brand-name drugs.
  • Tier 3: higher copayment, non-preferred brand-name drugs.
  • Specialty tier: highest copayment, very high-cost drugs.

Why the Drug List Changes

Plans set their costs and their drug lists for each new year. Medicare also allows a plan to change its list during the year, for example when new drugs are released or new medical information becomes available.

If a change affects a drug you take, Medicare says your plan must tell you. For most changes during the year, the plan must either give you written notice at least 30 days ahead, or give you notice at refill time along with at least a month’s supply under the old rules.

How to Check Your Medicines for Next Year

  1. Write down every medicine you take regularly, with the dose. A pharmacy printout works well.
  2. Find your plan’s Annual Notice of Change. It arrives in the fall and lists what is changing in January. Our guide shows how to read your Annual Notice of Change.
  3. Look up each medicine in your plan’s drug list for next year. You can find the list on the plan’s website, or call the member number on your plan card and ask.
  4. Note the tier for each medicine, and ask whether any coverage rules apply. Common ones are prior authorization (the plan must approve the drug before it pays), step therapy (you try a lower-cost drug first) and quantity limits (a cap on how much you can get at one time).
  5. Check that your pharmacy is still in the plan’s network.

If a Medicine Is Missing or Costs More

You have a few options, and you do not have to sort them out alone.

  • Talk to your prescriber. Medicare says that in most cases a similar drug should be on the list. Your doctor can tell you whether it would work for you.
  • Ask for an exception. If you or your prescriber believe none of the listed drugs will work, you can ask the plan to cover your drug, or to charge a lower-tier price for it.
  • Compare other plans. During open enrollment you can switch. Our step-by-step guide explains how to compare Medicare drug plans with your own medicine list on Medicare.gov.

When Changes Take Effect

If you switch, your new plan must receive your request by December 7, and the new coverage starts January 1. If you stay with your current plan, its new drug list and costs also start January 1.

If you join a new plan and one of your medicines is not on its list, Medicare’s guide says the plan will generally give you a one-time, temporary supply during your first 90 days. That gives you and your prescriber time to find a covered drug or ask for an exception.

Free Help and Help With Costs

  • 1-800-MEDICARE (1-800-633-4227). Medicare.gov says you can talk with a real person 24 hours a day, 7 days a week, except some federal holidays. TTY users can call 1-877-486-2048.
  • Your SHIP. State Health Insurance Assistance Programs give free, one-on-one Medicare counseling. Find yours at shiphelp.org.
  • Help paying. If drug costs are hard to manage, see our guides to Extra Help with drug costs and Medicare Savings Programs.

A safety reminder: no one from Medicare will pressure you to switch drug plans over the phone. If a caller asks for your Medicare Number or pushes you to sign up on the spot, hang up. You can read more in our Scams & Fraud section.

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