Which Part D Plans Work With Original Medicare

Part D plans work with Original Medicare, but not all plans are the same

Part D is prescription drug coverage you can add to Original Medicare (Parts A and B). You can choose any Part D plan offered in your area — there is no single plan that comes with Original Medicare. Each plan has its own list of covered drugs, costs, and pharmacies. The plans change every year, so the one you pick this year may not be the best choice next year.

Part D is run by private insurance companies, not Medicare directly. Medicare sets the rules, but each company decides which drugs to cover and how much you pay. You enroll during your Initial Enrollment Period (when you first become may be able to access for Medicare) or during the annual open enrollment period in the fall.

Key Takeaways

Any Part D plan sold in your state will work with Original Medicare — you do not need a Medicare Advantage plan to get drug coverage.
Part D plans vary widely in cost, deductibles, and which drugs they cover, so comparing plans in your area is necessary each year.
You enroll in Part D through Medicare.gov, by phone, or by mail during your enrollment window — missing it can mean a permanent penalty.
If you do not have prescription drug coverage from work or another source, you should enroll in Part D to avoid a late-enrollment penalty.

How to find Part D plans available in your area

Medicare publishes a list of all Part D plans offered where you live. You can search by ZIP code on Medicare.gov using the Plan Finder tool. The tool shows you each plan's monthly premium, annual deductible, copayments for different drugs, and which pharmacies participate.

The number of plans available varies by state and county. Some areas have 20 or more options; others have fewer. All plans must cover certain drugs (called "protected classes"), but beyond that, each plan's formulary — the list of covered drugs — is different. If you take specific medications, checking whether each plan covers them is the most important step.

You can also call Medicare at 1-800-MEDICARE (1-800-633-4227) and ask for a printed guide to plans in your area, or contact plans directly to request their formularies.

What Part D costs and how the coverage works

Part D has five cost stages: the deductible, the initial coverage period, the coverage gap (also called the "donut hole"), catastrophic coverage, and out-of-pocket maximums. Not all plans have a deductible — some start you in the initial coverage period right away.

During initial coverage, you pay a copayment or coinsurance for each prescription. Once your total drug costs (what you and the plan pay together) reach a certain amount, you enter the coverage gap. In the gap, you pay a larger share of the cost until your out-of-pocket spending reaches the catastrophic threshold. After that, the plan covers most of your drug costs for the rest of the year.

The exact amounts change each year. For 2024, the initial coverage limit was $5,850 in total drug costs, and the out-of-pocket maximum was $8,850. These figures are set by Medicare and explore to all plans, but your monthly premium and deductible depend on which plan you choose.

Enrollment windows and penalties for missing them

Your Initial Enrollment Period is the seven-month window that starts three months before the month you turn 65 (or become may be able to access for Medicare). If you enroll during this period, your coverage can start as early as the month you turn 65. If you miss it, you can still enroll later, but you may pay a permanent penalty.

The Annual Enrollment Period runs from October 15 to December 7 each year. During this time, you can switch to a different Part D plan or enroll in one for the first time. Changes take effect January 1.

If you go without Part D coverage for 63 days or more in a row (and you do not have other creditable prescription drug coverage), Medicare adds a penalty to your premium. The penalty is 1% of the national average Part D premium for each month you were uninsured. This penalty is permanent — it stays on your premium for as long as you have Part D.

Creditable coverage and when you do not need Part D

If you have prescription drug coverage through a current or former employer, a union, the Veterans Health Administration, or another source, that coverage may be creditable. Creditable means it is at least as good as Part D. If your coverage is creditable, you can delay enrolling in Part D without facing a penalty.

Your employer or plan administrator should tell you in writing whether your coverage is creditable. Keep that letter — you will need it if you enroll in Part D later. If you are unsure, contact your plan directly and ask whether your drug coverage meets Medicare's standards.

If you lose creditable coverage (for example, you retire and lose employer coverage), you have 63 days to enroll in Part D without a penalty. After 63 days, the penalty clock starts.

Switching plans and making changes during the year

You can switch to a different Part D plan only during the Annual Enrollment Period (October 15 to December 7) or if you may have access to for a Special Enrollment Period. Special Enrollment Periods are triggered by life events such as losing employer coverage, moving to a new state, or being determined to have low income.

If your current plan stops covering a drug you need, or if your costs change significantly, contact Medicare to see whether you may have access to for a Special Enrollment Period. You cannot switch plans outside these windows just because you want to — the rule exists to keep people from constantly changing coverage.

How Part D coordinates with Original Medicare and other coverage

Part D is separate from Parts A and B. You pay for Part A and B through Medicare, and you pay for Part D through the insurance company running the plan. If you also have supplemental coverage (called Medigap), that coverage works alongside both Original Medicare and Part D — it helps pay some of the costs that Medicare does not cover.

If you have Medicaid (state health insurance for people with low income), Medicaid may help pay your Part D premiums and cost-sharing. The rules vary by state. Contact your state Medicaid office to learn what help is available to you.

If you have Medicare Advantage (Part C) instead of Original Medicare, you cannot enroll in a standalone Part D plan. Medicare Advantage plans include drug coverage built in. You choose your drug coverage when you choose your Medicare Advantage plan.

Frequently Asked Questions

Do I have to enroll in Part D if I have Original Medicare?

Part D is optional, but if you do not have other creditable drug coverage and you do not enroll when you are first may be able to access, you will pay a permanent penalty. The penalty applies even if you enroll later and go years without using it. If you rarely take medications, it is still usually cheaper to enroll in a low-premium plan than to pay the penalty.

Can I switch Part D plans if my drug is no longer covered?

If your plan stops covering a drug you take, you may be able to request a coverage exception from your plan, or you may may have access to for a Special Enrollment Period that lets you switch plans outside the normal enrollment window. Contact your plan first to ask about an exception; if that does not work, call Medicare to ask about your options.

What happens if I move to a different state?

Part D plans are state-specific. If you move, your current plan may not be available in your new state. You have 60 days after you move to enroll in a new plan without a penalty. Use Medicare Plan Finder to see what plans are available in your new location.

How do I know if my employer coverage is creditable?

Your employer or plan administrator must send you a written notice each year stating whether your drug coverage is creditable. If you do not receive one, contact your benefits office or plan directly and ask. Keep the letter — you will need it as proof if you enroll in Part D later.

Can I get help paying for Part D premiums and costs?

If you have limited income and resources, you may be may be able to access for the Low-Income Subsidy program, which helps pay Part D premiums and cost-sharing. You can explore through Social Security, your state Medicaid office, or by calling 1-800-MEDICARE. may be able to access and benefit amounts vary by state and income level.

This guide is for general information only and is not medical, financial, legal, or other professional advice. For decisions specific to your situation, consult a qualified professional. See our Editorial Policy.