What Medicare Part D covers

Medicare Part D is prescription drug coverage run by private insurance companies approved by Medicare. It pays toward the cost of medications your doctor prescribes — both brand-name and generic drugs. Part D is optional, but if you don't sign up when you first become may be able to access, you may pay a penalty for as long as you have Medicare.

Part D covers thousands of medications, but not all of them. Each insurance company that offers Part D creates its own list, called a formulary, which shows which drugs are covered and at what cost. Your doctor's medication might be on one company's formulary but not another's, so comparing plans matters if you take specific drugs regularly.

The coverage includes prescription pills, inhalers, injections, and some other medications you pick up at a pharmacy. It does not cover over-the-counter drugs, vitamins, or cosmetic medications. Some medications require your doctor to get prior approval from the insurance company before the pharmacy will fill them.

Key Takeaways

  • Part D is optional prescription drug coverage, but skipping it when you first become may be able to access can result in a permanent penalty added to your premium.
  • Each Part D plan has its own formulary — the list of covered drugs — so you need to check whether your specific medications are covered before you choose a plan.
  • You can change Part D plans once a year during the Annual Enrollment Period (October 15 to December 7), or if you have a may have access to life event.
  • Part D costs include a monthly premium, an annual deductible, copayments or coinsurance, and potentially higher costs once you reach a spending threshold called the coverage gap.

How Part D costs are structured

Part D has four cost layers. First, you pay a monthly premium to the insurance company — this varies by plan and by region. Second, you pay an annual deductible before the plan starts paying anything; this amount also varies by plan and changes each year.

Once you meet your deductible, you pay copayments (a flat dollar amount per prescription) or coinsurance (a percentage of the drug's cost) each time you fill a prescription. These amounts depend on which "tier" your medication falls into — generic drugs are usually the lowest tier and cost less, while brand-name drugs are higher tiers and cost more.

If your total drug spending reaches a certain amount in a calendar year, you enter the coverage gap, sometimes called the "donut hole." In the gap, you pay a larger share of drug costs until your out-of-pocket spending reaches a yearly limit. Once you hit that limit, catastrophic coverage kicks in and the plan pays most of the cost for the rest of the year.

When you can sign up for Part D

You can sign up for Part D when you first become may be able to access for Medicare — usually at age 65. If you are already on Medicare, you can change plans or sign up for the first time during the Annual Enrollment Period, which runs from October 15 to December 7 each year. Changes take effect January 1.

You can also sign up outside the enrollment period if you have a may have access to life event, such as losing other drug coverage, moving to a different state, or a significant change in your income. You have 63 days from the date of the event to sign up. If you miss this window, you may have to wait until the next Annual Enrollment Period.

If you delay signing up for Part D when you first become may be able to access and you don't have other creditable drug coverage, you will owe a late enrollment penalty. This penalty is added to your premium for as long as you have Part D, so signing up on time matters even if you don't take many medications now.

How to find and compare Part D plans

Medicare.gov has a tool called the Medicare Plan Finder where you can enter your medications and see which plans cover them and at what cost. You will need a list of your current prescriptions, including the drug name, strength, and how often you take it. The tool shows you the estimated yearly cost for each plan, including premiums, deductibles, and copayments.

You can also call 1-800-MEDICARE (1-800-633-4227) and speak with a representative who can walk you through plan options. Many states also have State Health Insurance information Programs (SHIPs) that offer free, one-on-one counseling to help you compare plans. You can find your state's SHIP by calling 1-800-MEDICARE or visiting the Eldercare Locator at eldercare.acl.gov.

When comparing plans, look at the total estimated cost for a full year, not just the premium. A plan with a lower premium might have higher copayments or a higher deductible, so the math matters. Also check whether your pharmacy is in the plan's network — some plans have preferred pharmacies where your copayments are lower.

What happens if your medication is not covered

If your Part D plan does not cover a medication your doctor prescribed, you have options. You can ask your doctor whether a different medication on the formulary would work for you. Many plans cover multiple drugs in the same category, so an alternative might be available.

You can also request an exception from the insurance company. Your doctor submits a form explaining why this specific drug is medically necessary for you. The insurance company reviews the request and may approve it, which means the drug becomes covered under your plan. This process usually takes a few days to a week.

If the exception is denied, you can file an appeal. You have the right to ask for a review by someone outside the insurance company. Your doctor or pharmacist can help you understand your options and support your appeal if needed.

Part D and other Medicare coverage

Part D works alongside Original Medicare (Parts A and B) or Medicare Advantage (Part C). If you have Original Medicare, you choose a standalone Part D plan. If you have Medicare Advantage, the plan usually includes drug coverage built in, though you can sometimes switch to a standalone Part D plan instead.

If you have other drug coverage — such as coverage through a current or former employer, a union, or Medicaid — you may not need Part D right away. However, if that coverage ends, you have 63 days to sign up for Part D without a late penalty. Keep records of when your other coverage ends so you know your important date.

Low-income seniors may be able to get help paying Part D costs through the Low-Income Subsidy (LIS) program, also called "Extra Help." This program can lower your premiums, deductibles, and copayments. You can learn whether you may be may be able to access by calling 1-800-MEDICARE or visiting the Social Security Administration website.

Frequently Asked Questions

Can I switch Part D plans if I realize I chose the wrong one?

Yes, during the Annual Enrollment Period (October 15 to December 7), you can switch to a different Part D plan. The new plan takes effect January 1. If you have a may have access to life event — such as losing other coverage or moving — you can switch outside the enrollment period within 63 days of the event.

What if my medication costs more than my plan's copayment?

You pay only the copayment your plan sets, not the full price. The insurance company and pharmacy negotiate the actual price, and you are responsible only for your share. If you think the copayment is too high, ask your pharmacist whether a generic version or a different medication in the same category has a lower copayment.

Do I have to use a specific pharmacy for Part D?

Most Part D plans have a network of pharmacies where your copayments are lower. You can use an out-of-network pharmacy, but you will usually pay more. Check your plan's pharmacy list before you choose a plan, especially if you have a pharmacy you prefer or if it is close to your home.

What if I can't afford my Part D copayments?

If your income is low, you may be may be able to access for the Low-Income Subsidy program, which can reduce or eliminate your copayments. You can also ask your doctor or pharmacist about patient information programs run by drug manufacturers — many offer free or low-cost medications to people who meet income requirements.

Does Part D cover mail-order prescriptions?

Most Part D plans cover mail-order pharmacy services, and many offer lower copayments for 90-day supplies ordered by mail. Check your plan's details to see whether mail-order is available and what the copayment is. Mail-order can be convenient for medications you take regularly and don't need to change often.