Medicare Part D plans are required to cover "all or substantially all" drugs in six protected therapeutic classes to ensure beneficiaries with specific, serious health conditions have access to necessary medications. These protected classes are: immunosuppressants (transplant), antiretrovirals (HIV/AIDS), antidepressants, antipsychotics, anticonvulsants (seizures), and antineoplastics (cancer).
Part D plans are required to cover all drugs in six “protected” classes: immunosuppressants, antidepressants, antipsychotics, anticonvulsants, antiretrovirals, and antineoplastics.
Medicare Part D covers most prescription drugs, including brand-name and generic, through plan-specific lists called formularies, with mandatory coverage for six "protected" drug classes (cancer, HIV/AIDS, antidepressants, antipsychotics, anticonvulsants, immunosuppressants) and most vaccines, but generally excludes drugs for weight loss, fertility, and some vitamins, with coverage tiered by cost.
Medicare Part D generally excludes drugs for weight loss/gain, cosmetic purposes (like hair growth), fertility, and most cough/cold relief, plus non-prescription (OTC) meds and most vitamins (except prenatal/fluoride). Specific examples include Viagra (for ED), Propecia (hair loss), Xenical (weight loss), and Robitussin AC. Coverage varies by plan, but these categories are national guidelines.
Protected Classes
The protected classes include: age, ancestry, color, disability, ethnicity, gender, gender identity or expression, genetic information, HIV/AIDS status, military status, national origin, pregnancy, race, religion, sex, sexual orientation, or veteran status, or any other bases under the law.
A new cap on out-of-pocket costs for prescription drugs
As part of the Inflation Reduction Act in 2026, Medicare Part D enrollees will enjoy the security of a $2,100 cap on out-of-pocket prescription drug costs. This includes any deductibles,* copays and coinsurance paid, but not premiums.
Tier 1 – lowest copay: This tier includes lower-cost, commonly-used generic drugs. Tier 2 – low copay: This tier includes most generic drugs. Tier 3 – medium copay: This tier includes many common brand name drugs (preferred brands) and some higher-cost generic drugs.
Medicare Part D covers most prescription drugs, including brand-name and generic, through plan-specific lists called formularies, with mandatory coverage for six "protected" drug classes (cancer, HIV/AIDS, antidepressants, antipsychotics, anticonvulsants, immunosuppressants) and most vaccines, but generally excludes drugs for weight loss, fertility, and some vitamins, with coverage tiered by cost.
Beginning January 1, 2026, multivitamin combination products will no longer be covered. Single-ingredient vitamins and dry-eye treatments will require prior authorization to demonstrate medical necessity, while coverage of first- and second-generation antihistamines will be restricted to generic formulations.
How do I find if a Medicare Part D plan covers my prescription drugs? The best way to see if your prescription drugs are covered is to check the plan's formulary.
Over-the-counter (OTC) drugs may be purchased without a prescription. Medicare Part D does not cover OTC drugs under their basic prescription drug benefit or as a supplemental benefit under enhanced alternative coverage.
Medicare Part D prescription plans don't cover medications used for cosmetic purposes, erectile dysfunction, and hair loss. Over-the-counter medications also are not covered.
Tier 3 is generally more expensive than Tier 1 in health insurance and prescription drug plans, with Tier 1 being the lowest cost (usually generics) and Tier 3 typically covering preferred brand-name or higher-cost drugs, leading to higher copays or coinsurance, though plan structures can vary.
For 2026, the Medicare Part D maximum out-of-pocket (MOOP) drug cost is capped at $2,100, meaning once you spend that much on covered medications (including deductibles, copays, and coinsurance), your plan pays 100% for the rest of the year. This cap, a change from the Inflation Reduction Act, applies to all Part D plans and Medicare Advantage drug plans and simplifies costs, with no more coverage gap.
You may have to pay more, depending on your income. Who pays a higher Part D premium because of income? You'll pay an extra 1% for each month you could have signed up for Part D, but didn't, and didn't have creditable drug coverage. We'll add this penalty to your monthly Part D premium.
To be eligible for a Medicare Part D plan, you must first have Medicare Part A and/or Part B, and then live in the plan's service area, usually requiring U.S. citizenship or lawful presence. Essentially, you need to already be in the Medicare system and reside where the specific drug plan operates to add prescription coverage.
If you voluntarily enrolled with Part D and you are not considered dual eligible, you may dis-enroll from Medicare Part D. However, you may pay a higher premium, later if you decide to re-enroll with Medicare Part D.