Medicare 2026

Part D's Six Protected Drug Classes: The Medicines Plans Must Cover

If you take medication for a serious or ongoing condition, one of the most reassuring things to know about Medicare Part D is that every plan has to cover "all or substantially all" of the drugs in six categories called the protected classes. These are medications where swapping or delaying treatment can cause real harm, so the rules are stricter than for the rest of the formulary. Here is what that means in plain terms, and how to use it when you're comparing or using a plan.

What the six protected classes are

Under Part D program rules, every stand-alone Part D plan and every Medicare Advantage plan that includes drug coverage must include all or substantially all drugs in these six classes:

• Anticonvulsants (for seizure disorders)
• Antidepressants
• Antineoplastics (cancer medications)
• Antipsychotics
• Antiretrovirals (HIV medications)
• Immunosuppressants (to prevent transplant rejection)

Outside these six classes, plans have more flexibility: for other drug categories, a plan must include at least two drugs. That is why one plan's formulary can look quite different from another's for, say, blood pressure or cholesterol medicines, even though the protected-class lists tend to be comprehensive.

"Must cover" does not mean "no rules"

This is the piece people most often miss. A plan covering a protected-class drug still gets to decide:

• Which tier the drug sits on (which affects your cost share), and
• Whether to apply utilization management tools like prior authorization, step therapy, or quantity limits.

So two plans might both cover the same antidepressant, but one may put it on a preferred tier with a modest copay and the other may put it on a higher tier and require prior authorization. The plan's formulary document shows the tier and any rules for each drug. Before enrolling, it's worth looking up every medication you take on the plan's drug list.

Exceptions: your right to push back

If a drug you need isn't on the formulary, or a rule is standing in your way, you can ask the plan for an exception.

• A formulary exception asks the plan to cover a drug that isn't on its list, or to waive a rule such as prior authorization, step therapy, or a quantity limit.
• A tiering exception asks the plan to charge you a lower tier's cost sharing for a non-preferred drug. Plans are allowed to decline tiering exceptions for drugs on their specialty tier.

Your prescriber's supporting statement is usually central to these requests. If the plan says no, there is a formal appeal process; Medicare.gov walks through the steps.

The 90-day transition supply

When you first join a new Part D plan — or when your current plan changes its formulary at the start of a new year — you might find a medication you've been taking is no longer covered the same way. Generally, during your first 90 days in the new plan, you can get a one-time temporary (transition) supply of a drug you already take that isn't on the new plan's formulary. That window gives you time to work with your prescriber to switch to a covered alternative or request an exception.

What you'll pay in 2027

A few national Part D figures are set for 2027:

• The out-of-pocket cap is $2,400. Once your own spending on covered Part D drugs reaches that amount in the year, you pay nothing more for covered Part D drugs for the rest of the year.
• The maximum deductible a plan may charge is $700 (plans may charge less).
• The base beneficiary premium is $41.33. This is a national figure used in calculating the late-enrollment penalty; actual plan premiums are set plan by plan and vary.

Because premiums, deductibles, tiers, and copays vary from plan to plan, the only way to know your real costs is to look at the specific plan's documents.

When you can enroll or switch

The Annual Enrollment Period runs October 15 through December 7, 2026, with choices taking effect January 1, 2027. This is the window most people use to join, drop, or change a Part D or Medicare Advantage plan.

If you have Medicaid or qualify for Extra Help, you have an additional monthly Special Enrollment Period that lets you move to Original Medicare paired with a stand-alone Part D plan, or switch stand-alone Part D plans. Full-benefit dual-eligible individuals may also join an integrated D-SNP in any month.

Original Medicare + Medigap vs. Medicare Advantage: a neutral note

Protected-class rules apply to Part D drug coverage regardless of how you get the rest of your Medicare. With Original Medicare, you typically add a stand-alone Part D plan and may add a Medigap policy to help with Part A and Part B cost sharing; you generally have broad provider choice. With Medicare Advantage, drug coverage is usually bundled in, and plans may add extra benefits but typically use provider networks and plan rules. Neither is "better" in the abstract — the right fit depends on your medications, providers, budget, and preferences.

Where to go next

For official plan details, formularies, and side-by-side comparisons, use the Plan Finder and other tools at Medicare.gov, or call 1-800-MEDICARE (1-800-633-4227), available 24/7 (TTY 1-877-486-2048). Having your drug list and preferred pharmacy on hand will make the comparison much faster — and will help you confirm that the plan you're considering treats your protected-class medications the way you need it to.