Transition Supply Part D: The 30-Day Refill Rule When Switching Drug Plans

Your parent just switched Part D plans and showed up at the pharmacy in January only to hear that their blood thinner isn't on the new formulary. They're down to three days of pills. This is the exact scenario CMS's transition supply rules exist to prevent — but most families don't know about them until they're standing at the counter in a panic.

What the Transition Supply Rule Requires

Every Part D plan must provide a one-time, temporary supply of a beneficiary's current medications during certain transition situations, even if those drugs aren't on the new plan's formulary. CMS requires this to prevent dangerous gaps in therapy when coverage changes.

The transition supply is typically a 30-day fill at a retail pharmacy or a 90-day fill through mail order. The plan must cover it at the applicable cost-sharing level (copay or coinsurance) — not at full retail price.

When Transition Supply Applies

The 30-day transition rule kicks in during these situations:

• New enrollment in a Part D plan — switching from one PDP to another during the Annual Election Period, or enrolling in Part D for the first time
• Switching from a Medicare Advantage plan to a standalone PDP (or vice versa)
• Moving into a long-term care facility — residents of nursing homes and other institutions get an extended transition period
• Losing Extra Help status — if your parent's subsidy level changes, triggering a plan reassignment

The rule covers the first 90 days of enrollment in the new plan. During this window, your parent can fill current prescriptions while you and the doctor work on getting the medication either added to the new plan's formulary through an exception request or replaced with a covered alternative.

How to Use the Transition Supply

Step 1: Have the pharmacy submit the claim normally. The pharmacist should process the prescription under the new plan. If the system rejects it, the pharmacist should call the plan's pharmacy help desk and specifically request a transition supply override.

Step 2: Ask for the transition fill explicitly. Not all pharmacy staff know the transition supply rules. If you get pushback, cite the CMS requirement: "Part D plans are required under 42 CFR § 423.120(b)(3) to provide a temporary transition supply for current medications during a plan change."

Step 3: Use the 30-day window strategically. The transition fill buys you time, but it's a one-shot deal for each medication. During those 30 days, contact your parent's doctor to either:

• Submit a formulary exception request asking the new plan to cover the drug
• Identify a therapeutically equivalent medication that is on the new plan's formulary

Long-Term Care Facility Exception

If your parent lives in a nursing home or skilled nursing facility, transition supply rules are more generous. Plans must provide emergency or provisional supplies of non-formulary drugs for residents to prevent medication interruptions that could cause hospitalization. The facility's consulting pharmacist can often coordinate directly with the plan to extend the transition period.

What to Do If the Plan Refuses

If the pharmacy can't process a transition fill and the plan's phone line denies the request, file a formal coverage determination immediately. Request expedited processing (24-hour turnaround) if going without the medication poses a health risk. The initial coverage determination must be decided within 72 hours for standard requests; if it is denied, the first-level redetermination is generally decided within 7 days.

In the meantime, ask the prescribing doctor for samples or a short-term prescription to bridge the gap.

For a printable transition checklist that tracks each medication's formulary status across old and new plans, the Medicare Part D: How to Choose a Drug Plan guide includes a plan-switching workflow designed to prevent pharmacy surprises on day one.

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