Medicare and Prescriptions: How Part D Drug Plans Work

If you take prescription medications — and most Medicare beneficiaries do — Part D is one of the most financially significant decisions you'll make during enrollment. A plan that covers your drugs well can mean hundreds of dollars in savings per year. A plan that doesn't can cost you far more than you expected.

Here's how Part D actually works, broken down clearly.

What Part D Is

Medicare Part D is prescription drug coverage. It's offered by private insurance companies that have contracted with Medicare. Plans are regulated by CMS (Centers for Medicare & Medicaid Services), which sets minimum standards — but individual plans vary significantly in which drugs they cover, how much you pay, and what pharmacies they work with.

You can get Part D coverage two ways:

1. Standalone Part D plan — added to Original Medicare (Parts A + B). You'll have a separate insurance card and premium for drug coverage.
2. Bundled in a Medicare Advantage plan — most Medicare Advantage plans include Part D coverage as part of the package.

What Part D Covers

Each Part D plan covers a list of drugs called a formulary. The formulary is organized into tiers, with different cost levels:

• Tier 1 – Preferred generic drugs: Lowest copays, often $0–$5
• Tier 2 – Non-preferred generics: Slightly higher copays
• Tier 3 – Preferred brand-name drugs: Moderate copays or coinsurance
• Tier 4 – Non-preferred brand drugs: Higher coinsurance, often 25–40%
• Tier 5 – Specialty drugs: Very expensive drugs; high coinsurance

If a drug isn't on the formulary, you generally pay the full cost. You can request an exception — asking the plan to cover a drug not on its formulary — but it requires your doctor to provide medical justification.

Formularies change every year. A drug that was covered in 2024 may move to a higher tier or be removed entirely in 2025. This is one key reason to review your Part D coverage every Annual Enrollment Period.

What Part D Costs

Part D has several layers of costs:

Monthly premium: Varies by plan, typically $10–$100+/month. Plans with higher premiums often have lower cost-sharing for specific drugs.

Annual deductible: Most plans charge a deductible before coverage kicks in. In 2025, the maximum deductible is $590. Some plans waive the deductible for lower-tier drugs.

Copays and coinsurance: After the deductible, you share costs with the plan based on the tier your drug falls in.

Out-of-pocket cap (2025 major change): Beginning in 2025, once you've spent $2,000 out of pocket on covered drugs, you pay nothing more for covered prescriptions for the rest of the calendar year. This is a significant protection that didn't exist in this form in prior years.

IRMAA for Part D: Higher-income beneficiaries also pay an income-related surcharge on their Part D premium, similar to the IRMAA applied to Part B.

The Medicare Prescription Payment Plan

A new option in 2025 allows you to smooth out drug costs across the year. Instead of paying large amounts all at once early in the year (when deductibles and cost-sharing can pile up), you can opt into the Medicare Prescription Payment Plan, which spreads your drug cost-sharing into equal monthly payments from January through December.

This doesn't reduce the total amount you owe — it just makes the timing more manageable. It can be especially helpful for people on fixed monthly incomes.

How to Compare Part D Plans

This is where most people go wrong: they pick a plan based on the monthly premium and call it done. That's often a costly approach.

The right way to compare Part D plans:

1. List all your current medications — generic and brand names, dosages, how often you take them
2. Go to medicare.gov and use the Plan Finder tool — it lets you enter your drugs and compare your estimated total annual cost across all plans in your area
3. Check that your preferred pharmacy is in-network — using a preferred pharmacy often significantly reduces your copays
4. Look at the deductible and tier placement for your specific drugs, not just the premium
5. Consider mail-order pharmacy — many plans offer reduced copays for 90-day supplies through mail order

The Plan Finder at medicare.gov is genuinely useful. Use it every fall during Annual Enrollment Period — even if you're satisfied with your current plan — because formularies and costs change.

Extra Help / Low-Income Subsidy (LIS)

If your income and resources are limited, you may qualify for Extra Help (also called the Low-Income Subsidy or LIS). This federal program helps pay for Part D premiums, deductibles, and copays.

In 2025, the income limit for full Extra Help is approximately 135% of the federal poverty level (around $20,783/year for an individual). A partial subsidy is available up to 150% FPL.

People who qualify for Extra Help pay significantly reduced Part D costs — often $0 premiums and very low copays. Extra Help is separate from Medicaid but works alongside it for dual-eligible beneficiaries.

To apply for Extra Help, contact Social Security at 1-800-772-1213 or apply online at ssa.gov/extrahelp.

Late Enrollment Penalty for Part D

If you go without creditable prescription drug coverage for 63 or more consecutive days after your Initial Enrollment Period ends, you'll owe a late enrollment penalty when you do sign up. The penalty is calculated as 1% of the national average premium for each month you were without coverage — and it's permanent.

Even if you don't currently take prescriptions, enrolling in a low-cost Part D plan when you first become eligible is generally worth considering to avoid this penalty.

Understanding Your Medications Before You Enroll

Drug coverage decisions are highly personal. Two people can have the same plan and have very different experiences depending on which medications they take. Before you lock in your Part D choice:

• Run your specific drug list through the Plan Finder
• Call the plan to confirm your medications are covered before enrolling
• Ask your doctor if therapeutic alternatives exist that might be lower-cost on a given formulary

Making an informed Part D choice can be one of the most financially meaningful Medicare decisions you make each year.

---

Have questions? Call 1-877-443-3251 for free, no-obligation help from a licensed agent.

This is an educational website and is not affiliated with or endorsed by Medicare or any government agency. We connect consumers with licensed insurance agents who can help with Medicare enrollment. Not all plans or options are available in all areas. Please contact Medicare.gov, 1-800-MEDICARE, or your local State Health Insurance Program (SHIP) to get information on all of your options.