Medicare 2026

Switching Part D Plans? How the Transition Fill Protects You When Your New Plan Doesn't Cover a Drug

Changing Part D plans can feel like a leap of faith, especially if you take a prescription that keeps your days steady. What happens on January 1 if your new plan's formulary looks different from your old one? Federal rules build in a safety net called a transition fill. It gives you time to work things out without going without medication. Here is how it works, who it covers, and what to do next.

Why the transition fill exists

Every Part D plan has its own formulary — the list of drugs it covers and the rules it applies, like prior authorization or step therapy. When you switch plans, join Medicare for the first time, or stay in a plan that changes its formulary for the new year, your longtime prescription may suddenly fall outside the coverage lines. Federal rules recognize this and require every Part D plan to run a transition process so you don't lose access to a medicine while details get sorted out.

The transition process applies to:

• New enrollees after the Annual Enrollment Period
• People newly eligible for Medicare
• People who switch plans after the year starts
• Current members whose drug was affected by a formulary change

It does not apply to changes a plan is allowed to make immediately, such as removing a drug that has been pulled from the market for safety reasons.

What the temporary supply looks like

Within the first 90 days of coverage under your new plan, the plan must give you a one-time, temporary supply of at least a month's worth of a drug you've been taking that isn't on the formulary, or that requires prior authorization or step therapy. Medicare.gov describes this as a one-time 30-day supply. If your prescription is written for less than a month, the plan has to let you refill it up to that one-month amount.

After that fill goes through, the plan must send you a written notice within 3 business days explaining what happened and what your options are. It also has to make reasonable efforts to let your prescriber know.

What a transition fill costs

For people who get Extra Help, a transition fill can cost no more than the statutory maximum copayments. For everyone else, the cost is the same as the plan charges for a drug approved through a formulary exception — or what it would charge once prior authorization or step therapy criteria are met. In other words, the transition fill isn't priced as a penalty for being caught in the middle.

Using the breathing room: ask for an exception

The transition fill is a bridge, not a long-term fix. If you need to stay on a drug the new plan doesn't cover, you or your prescriber can ask the plan for an exception — a decision by the plan to cover a drug that isn't on its formulary, or to waive a coverage rule like prior authorization or step therapy. Your prescriber must provide a supporting statement that explains the medical reason you need this specific drug.

Timelines are set in federal rules:

• A standard coverage request: no later than 72 hours after the plan receives it (for an exception, 72 hours after it receives the prescriber's supporting statement).
• An expedited request (when waiting could seriously harm your health): no later than 24 hours (for an exception, 24 hours after receiving the supporting statement).

If the plan says no, there's a formal appeal process. Medicare.gov walks through each level.

At the pharmacy counter

If your pharmacist tries to fill the prescription and it gets rejected, you should receive a written notice explaining how you or your prescriber can ask the plan for a coverage decision. You don't have to wait for that moment either — you can ask your plan for a coverage decision before you even go to the pharmacy, which can save a trip.

When this comes up most often

The busiest window for transition fills is early January, right after Annual Enrollment choices take effect. Annual Enrollment for 2027 coverage runs October 15 through December 7, 2026, with new coverage starting January 1, 2027. If you chose a different plan during that window, pull out your new plan's formulary before January and compare it to your current drugs. Catching a mismatch early means you can start an exception request on day one rather than scrambling at the pharmacy.

A few other moments can trigger the same protection: becoming newly eligible for Medicare, switching plans mid-year under a Special Enrollment Period, or staying with your plan while its formulary changes for the new year.

A note for people with Medicaid or Extra Help

Since 2025, people with Medicaid or Extra Help have a monthly Special Enrollment Period to move to Original Medicare with a stand-alone Part D plan, or to switch stand-alone Part D plans. Full-benefit dual-eligible individuals can also join an integrated D-SNP in any month. If you use these monthly options to change plans mid-year, the transition fill rules travel with you — your new plan must still provide the temporary supply if a current drug isn't covered.

What should people with Medicare know about drug list changes and the ANOC?

The 2027 Part D out-of-pocket cap is $2,400 (it is $2,100 in 2026), and no Part D plan may charge a deductible higher than $700 in 2027. Those protections matter for everyday affordability, but the transition fill is the specific rule that keeps a plan change from becoming a medication gap. Know it exists, use the 90-day window, and start the exception conversation with your prescriber early.

Where can you get help with Medicare questions?

For plan-specific details, formularies, and coverage decisions, use the official tools at Medicare.gov or call 1-800-MEDICARE (1-800-633-4227), TTY 1-877-486-2048, available 24 hours a day, 7 days a week. This article is educational and independent; it is not from the federal government or any plan.