Lesson 4 of 6

Part D Drug Coverage — How It Works

Prescription drug coverage, the 2026 out-of-pocket cap, and why skipping Part D can be a costly mistake even if you don't take medications now.

Written by Kayla Price, Licensed Medicare Agent (NPN 18530055)

Quick Answer

Part D covers prescription drugs through private plans, either standalone or bundled into Medicare Advantage. As of 2026, your out-of-pocket costs on covered drugs are capped at $2,100 per year — after that, covered drugs cost $0 for the rest of the year.

How Part D Coverage Works

Unlike Part A and Part B, which are administered directly by the federal government, Part D is entirely run by private insurance companies operating under CMS rules. You choose a specific plan, and that plan determines your premium, deductible (if any), and which drugs it covers and at what cost — called the plan's formulary.

The 2026 Part D Out-of-Pocket Cap

$2,100 annual cap — once your out-of-pocket spending on covered Part D drugs reaches this amount in 2026, you owe $0 for the rest of the calendar year on those covered drugs. This is one of the most significant recent changes to Medicare, a result of the Inflation Reduction Act's drug pricing reforms, and it replaced the older "donut hole" coverage gap structure that used to leave beneficiaries with unpredictable costs mid-year.

Understanding Drug Formularies

Every Part D and Medicare Advantage plan maintains its own formulary — the specific list of drugs it covers, organized into cost tiers (generally, lower tiers for generics cost less than higher tiers for brand-name or specialty drugs). Two plans can have very different costs for the exact same medication, depending on which tier they place it in.

Formularies aren't fixed forever — plans can and do change their formularies from year to year, sometimes removing a drug or moving it to a higher tier. This is one of the key reasons annual plan comparison matters, even if you're happy with your current plan: a formulary change could quietly increase what you pay for a medication you've been taking for years.

Why Skipping Part D Can Backfire

It's tempting to skip Part D if you don't currently take any prescription medications — why pay a premium for something you're not using? The problem is the late enrollment penalty: if you go 63 or more continuous days without creditable prescription drug coverage (coverage at least as good as standard Medicare drug coverage) after your Initial Enrollment Period ends, enrolling later can trigger a permanent penalty added to your premium — even if the gap was years ago and even if you didn't need medications at the time.

For most people, enrolling in at least a low-cost standalone Part D plan during your Initial Enrollment Period — even with minimal current drug needs — is the safer path than risking a permanent penalty later. See our full breakdown of this and other common Medicare mistakes for more detail.

The penalty itself is calculated as roughly 1% of the national base beneficiary premium for each full month you went without creditable coverage, rounded to the nearest 10 cents, and it's added to your monthly Part D premium for as long as you have Part D coverage. Because the national base premium can change each year, the exact dollar amount of the penalty can shift slightly year to year even though the percentage calculation stays consistent — but the core lesson doesn't change: the earlier you close this gap, the less it costs you over time.

Frequently Asked Questions

What is Medicare Part D?

Part D is Medicare's prescription drug coverage, sold by private insurance companies either as a standalone plan (alongside Original Medicare) or bundled into a Medicare Advantage plan.

What is the Part D out-of-pocket cap in 2026?

As of 2026, Part D has a $2,100 annual out-of-pocket cap on covered drugs. Once you hit that amount in a calendar year, you pay $0 for the rest of the year for covered Part D drugs.

What happens if I don't sign up for Part D?

If you go 63 or more continuous days without creditable prescription drug coverage after your Initial Enrollment Period ends, you can face a permanent late enrollment penalty when you eventually enroll — even if you don't take medications now.

What is a drug formulary?

A formulary is the list of drugs a specific Part D or Medicare Advantage plan covers, organized into cost tiers. Formularies vary by plan and can change year to year, which is why checking your specific medications against a plan's formulary before enrolling matters.

Want help comparing Part D plans for your medications?

Kayla Price is a licensed insurance agent (NPN 18530055) offering free, no-pressure consultations. Call (866) 648-1578.