Here's the short answer. Every Part D and Medicare Advantage drug plan can change its formulary — the list of covered drugs — every January. Check your plan's Annual Notice of Change, mailed by September 30, for any of your drugs listed as dropped or moved to a higher tier. If your drug isn't covered the way it used to be, you have until December 7 to switch plans during Open Enrollment, with the new plan starting January 1.
Step 1: Find your plan's 2027 drug list
Your plan's formulary for next year shows up in three places:
- The Annual Notice of Change (ANOC), mailed by September 30, which flags what's changing.
- The Evidence of Coverage (EOC), mailed or made available by October 15, with the complete rulebook.
- Medicare Plan Finder, where entering your drugs shows the tier and any coverage rules for each plan in your area.
Step 2: Check every drug against three questions
For each prescription you take, ask:
- Is it still on the formulary at all? Plans can drop a drug entirely from one year to the next.
- Did its tier change? The ANOC flags drugs moved to a higher-cost tier.
- Did a new coverage rule get added? Plans can add prior authorization (approval needed before the plan pays), step therapy (try a cheaper drug first), or a quantity limit, even for a drug that stays on the list.
Do this for every drug you take, not just the most expensive one. A single dropped generic can still mean an unplanned full-price fill in January.
Step 3: Decide what to do about a problem drug
If a drug you need is dropped, moved to a higher tier, or newly restricted, you have two paths:
- Switch plans during Open Enrollment. Compare other plans' formularies in Plan Finder and switch by December 7 so the new coverage starts January 1. See How to Compare Medicare Plans for 2027.
- Ask for a formulary exception. If you'd rather stay in your current plan, your prescriber can request an exception explaining why the drug is medically necessary for you. Our formulary exception and appeal guide walks through the request and the appeal deadlines if the plan says no.
If you miss it: the transition fill
If a covered drug you were taking is dropped or newly restricted when the new plan year starts, you may get a one-time, 30-day transition fill — enough medicine to buy time while you request an exception or switch plans.
Switching Medicare Advantage plans over a formulary problem
If the formulary issue is with a Medicare Advantage plan's drug coverage rather than a standalone Part D plan, the same December 7 deadline and Plan Finder process apply. See Switching Medicare Advantage Plans: What to Check First for the other things worth checking — network and total cost — before you move.
Common questions
Where do I find my Part D plan's 2027 drug list?
In your plan's Annual Notice of Change and Evidence of Coverage, mailed by September 30 and October 15, or on the plan's website, or through Medicare Plan Finder.
What if my drug is dropped and I don't catch it before December 7?
You may still get a one-time, 30-day transition fill when the new plan year starts, which buys time to ask for a formulary exception or switch plans through certain special enrollment periods.
Does a formulary change apply to Medicare Advantage plans too, or just standalone Part D plans?
Both. Any Medicare Advantage plan with drug coverage has its own formulary that can change every January, the same as a standalone Part D plan.
Official sources
- Medicare.gov: Drug plan coverage rules
- Medicare & You (PDF)
- Medicare.gov: Joining a plan
- Medicare Plan Finder