Medicare 2026

Switching Medicare Advantage Plans While You're In Treatment: How the 90-Day Transition Rule Protects You

Changing plans in the middle of chemotherapy, physical therapy, or a long course of specialist care is one of the most stressful things a Medicare beneficiary can face. A federal rule finalized by CMS in 2023 is designed to lower that stress. It requires Medicare Advantage coordinated care plans — HMOs and PPOs — to give new members at least a 90-day transition period during which an active course of treatment can continue without the new plan requiring fresh prior authorization. Here is what that means in practice, and how it fits with the enrollment choices you may be weighing for 2027.

What the 90-day transition rule says

In the final rule issued April 5, 2023 (CMS-4201-F) for the 2024 plan year, CMS required Medicare Advantage coordinated care plans to provide a minimum 90-day transition period for new enrollees who are undergoing treatment. The requirement lives in federal regulation at 42 CFR 422.112(b)(8). During those 90 days, the new plan may not require prior authorization for the active course of treatment, and it cannot disrupt care or demand reauthorization just because you switched plans.

The protection applies to basic, Medicare-covered benefits. It covers people who are new to a particular plan and people who are new to Medicare. Importantly, it covers care that began before you enrolled in the new plan — even when the provider furnishing that care is out of the new plan's network.

What counts as an "active course of treatment"

Under the rule, a course of treatment is a prescribed or ordered plan for a specific person with a specific condition, outlined and decided ahead of time by the patient and provider. It is "active" when the patient is actually seeing the provider and following the plan — think ongoing cancer therapy, cardiac rehabilitation, scheduled infusions, dialysis, or a structured post-surgical rehab program. A single appointment scheduled on a whim is not what the regulation is protecting; a documented, ongoing plan of care is.

After the 90 days: approvals that stick

The protections don't end abruptly at day 91. When a Medicare Advantage plan approves prior authorization for a course of treatment, that approval must remain valid for as long as the treatment is medically necessary, based on coverage criteria, your medical history, and your treating provider's recommendation. Medicare.gov is explicit that the plan cannot keep asking you to get additional approvals for the same treatment.

Furthermore, once a plan approves an item or service — whether through prior authorization, a pre-service decision, or a decision made during inpatient or outpatient care — it cannot later deny coverage on medical-necessity grounds and cannot reopen that decision except for good cause or reliable evidence of fraud or similar fault.

Limits on prior authorization

Coordinated care plans may use prior authorization only to confirm diagnoses or other medical criteria that form the basis for coverage, to ensure a basic benefit is medically necessary, or to ensure a supplemental benefit is clinically appropriate. A plan that uses utilization management must also have a utilization management committee, led by the plan's medical director, that reviews those policies at least once a year.

If a plan tries to cut off care

If a Medicare Advantage plan decides to reduce or stop a previously authorized ongoing course of treatment, that is a formal coverage decision — an organization determination. The plan must send you a written notice with the specific reasons, and it must explain your right to ask for a reconsideration, including an expedited (fast) reconsideration when waiting could jeopardize your health. Keep that notice; it is your starting point for an appeal.

How this fits into your enrollment choices

The 90-day transition rule applies to Medicare Advantage coordinated care plans. It is one of several factors to weigh when you compare Medicare Advantage with Original Medicare paired with a stand-alone Part D plan (and possibly a Medigap policy). Medicare Advantage bundles coverage and often includes extra benefits, but typically uses networks and prior authorization. Original Medicare lets you see any provider that accepts Medicare and generally does not use prior authorization for most services, but you manage drug coverage and supplemental coverage separately. Neither path is "better" in the abstract — the right fit depends on your health, providers, and budget.

Key dates to keep in mind: the Annual Enrollment Period for 2027 coverage runs October 15 through December 7, 2026, with changes effective January 1, 2027. For 2027, the Part D annual out-of-pocket cap is $2,400 (up from $2,100 in 2026), the maximum Part D deductible any plan may charge is $700, and the Part D base beneficiary premium — used to calculate the late-enrollment penalty — is $41.33. The 2027 Part B standard premium and deductible, along with the IRMAA income brackets, have not been announced; CMS typically releases those figures in the fall. The Social Security Administration announced a 3.6 percent COLA for benefits payable beginning January 2027.

Special rules for people with Medicaid or Extra Help

If you have Medicaid or qualify for Extra Help with Part D costs, you 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 Dual Eligible Special Needs Plan (D-SNP) in any month. If you are mid-treatment and use one of these opportunities to join a new Medicare Advantage or D-SNP plan, the 90-day transition protection applies to you too.

Where to go next

Before switching plans mid-treatment, talk with your treating providers about documenting your active course of treatment, and ask the plan you are considering how it handles transition-period claims and out-of-network billing during those 90 days. For official, plan-by-plan information and to compare coverage, visit Medicare.gov or call 1-800-MEDICARE (1-800-633-4227); TTY users can call 1-877-486-2048.

This article is educational and is published by a privately owned Medicare education site. It is not affiliated with or endorsed by the federal government or the Medicare program.