Prescription Drug Coverage (Medicare Part D)
Your medications can be one of the biggest factors in choosing Medicare coverage.
Medicare drug coverage is not one-size-fits-all. Premiums, pharmacies, formularies, deductibles, copays, and covered medications can vary depending on the plan and the prescriptions you take.
What Is Medicare Part D?
Medicare Part D helps pay for prescription medications. Part D coverage is offered through private insurance companies approved by Medicare.
If you use Original Medicare, you usually choose a separate Part D prescription drug plan. If you choose Medicare Advantage, prescription drug coverage may be included in the plan, but it still needs to be reviewed carefully.
A drug plan that works well for one person may be a poor fit for someone else. The right plan depends on your medications, dosage, pharmacy, and where you live.
How Part D Works
Monthly Cost
Some Part D plans have a monthly premium. A lower premium does not always mean the lowest total drug cost.
What You Pay First
Some plans have a deductible before certain drug coverage begins. Deductibles can change from year to year.
Covered Drug List
A formulary is the list of medications a plan covers. Your medications should be checked every year.
Drug Cost Levels
Plans often place drugs into tiers. A medication's tier can affect what you pay at the pharmacy.
Preferred Pharmacy Rules
Your cost may change depending on whether your pharmacy is preferred, standard, mail-order, or out of network.
What You Pay Per Fill
Copays and coinsurance can vary by drug, plan, pharmacy, and coverage stage.
Before You Choose a Drug Plan
Prescription coverage should start with your actual medication list, not with a plan name or monthly premium.
- What prescription medications do I take?
- What dosage and frequency do I use?
- Which pharmacy do I prefer?
- Do I use mail order?
- Are lower-cost generics available?
- Do I travel or live in more than one state?
- Could my medications change soon?
Why Drug Plans Should Be Reviewed Every Year
Part D plans can change each year. Even if your prescriptions stay the same, your costs may not.
Formularies Can Change
A drug covered this year may have different rules or costs next year.
Pharmacies Can Change
Your pharmacy may not have the same preferred pricing next year.
Premiums Can Change
A plan's monthly cost can increase or decrease from one year to the next.
Drug Tiers Can Change
A medication may move to a different tier, which can affect your cost.
This is why the Annual Enrollment Period, October 15 through December 7, matters. It is the time many people review Medicare Advantage and Part D prescription drug coverage for the next year.
Common Part D Mistakes
Choosing based only on premium
The lowest monthly premium may not be the lowest total cost if your medications are expensive under that plan.
Not checking the formulary
If your medication is not covered, or is covered with restrictions, your costs can change quickly.
Using the wrong pharmacy
Some plans price medications differently depending on the pharmacy you use.
Never reviewing your plan
Drug plans change every year. Staying in the same plan without reviewing it can lead to surprises.
Assuming Medicare Advantage drug coverage is always the same
Many Medicare Advantage plans include prescription coverage, but the covered medications, pharmacy rules, and costs vary by plan.
The Medicare Prescription Payment Plan
Beginning in 2025, Medicare offers the Medicare Prescription Payment Plan. This option allows people with Medicare drug coverage to spread certain out-of-pocket prescription drug costs over monthly payments during the year instead of paying all at once at the pharmacy.
This does not lower the total cost of the medications. It changes how those costs may be paid over the year.
This can be helpful for cash flow, but it is not the same as a discount, subsidy, or plan recommendation.
Bring This With You to a Medicare Review
A prescription review is only as good as the medication information being reviewed. Bring the real list, not your best guess.
- Prescription medication names
- Dosage and frequency
- Preferred pharmacy
- Mail-order pharmacy, if used
- Insulin or injectable medications
- Over-the-counter medications
- Vitamins and supplements
- Any medication you stopped recently or may start soon
Related Resources
Author: Michelle Heberling
Last Reviewed: July 2026
Sources: Medicare.gov, Centers for Medicare & Medicaid Services, Medicare & You Handbook