Which Part D Plans Work With Original Medicare

Part D Plans Are Separate From Original Medicare, Not Built In

Original Medicare (Part A and Part B) does not include prescription drug coverage. If you want drug coverage under Original Medicare, you must choose and enroll in a Part D plan — a separate insurance policy run by private insurance companies that Medicare approves. Part D is optional, but if you delay signing up when you first become may be able to access, you may pay a penalty for as long as you have Medicare.

Any Part D plan that is available in your state works with Original Medicare. There is no special "Original Medicare version" of Part D. When you enroll in Part D, you keep your Original Medicare coverage exactly as it is — Part D straightforward adds drug coverage on top.

Key Takeaways

Part D is a separate prescription drug plan you choose yourself; it is not automatic with Original Medicare.
You can use any Part D plan offered in your state, regardless of which Original Medicare coverage you have.
Part D plans vary widely in cost, deductibles, and which drugs they cover, so comparing plans before enrollment matters.
If you do not enroll in Part D when first may be able to access and later want it, you will owe a late enrollment penalty that increases the longer you wait.
You enroll in Part D through Medicare.gov or by calling 1-800-MEDICARE, separate from your Original Medicare enrollment.

How Part D Plans Differ From Each Other

All Part D plans cover the same categories of drugs — brand-name and generic medications — but each plan decides which specific drugs it will pay for and at what cost. One plan might cover your blood pressure medication with a $10 copay, while another plan covers the same drug but charges $50. A third plan might not cover it at all and require you to use a different medication instead.

Part D plans also differ in their deductibles (the amount you pay before the plan starts helping), monthly premiums, and how much you pay out of pocket before the plan covers most of your costs. Some plans have no deductible. Others charge $100 to $500 per year. The monthly premium can range from roughly $7 to $100 or more, depending on the plan and your location.

Because plans vary so much, the drugs you take should guide your choice. Medicare provides a plan comparison tool on Medicare.gov where you can enter your medications and see which plans cover them and at what cost. This step alone can save you hundreds of dollars per year.

When You Can Enroll in Part D

You have a seven-month window to enroll in Part D without penalty: the three months before the month you turn 65, the month you turn 65, and the three months after. If you miss this window, you can still enroll, but you will owe a late enrollment penalty that is added to your monthly premium for as long as you have Part D coverage.

The late enrollment penalty is roughly 1 percent of the national average Part D premium for each full month you were not enrolled when you could have been. If you delay for two years, the penalty compounds and becomes permanent. The only way to avoid the penalty is to have had other creditable drug coverage (through an employer, a union, the Veterans Administration, or another source) during the time you were not enrolled in Part D.

If you already have Original Medicare and realize you need drug coverage, you can enroll in Part D during the annual enrollment period from October 15 to December 7 each year. Coverage begins January 1 of the following year.

Where to Find and Compare Part D Plans

Medicare.gov has a plan finder tool that shows all Part D plans available in your zip code. You enter your medications, and the tool shows you which plans cover them, what you will pay at the pharmacy, and the monthly premium for each plan. This is the official source and costs nothing to use.

You can also call 1-800-MEDICARE to speak with someone who can help you compare plans over the phone. They cannot tell you which plan to choose, but they can walk you through the options and explain how each one works with your medications.

Some people work with insurance agents or brokers who specialize in Medicare. These agents are paid by the insurance companies, not by you, so there is no cost to use them. However, not all agents represent all plans, so you may want to check Medicare.gov yourself to make sure you are seeing all available options in your area.

What Happens After You Enroll in Part D

Once you enroll, you will receive a membership card in the mail. You show this card at the pharmacy when you fill a prescription. The pharmacy checks which drugs your plan covers and what you owe. You pay your share (copay, coinsurance, or the full price if the drug is not covered), and the plan pays the rest to the pharmacy.

Your Part D coverage runs on a calendar year. On January 1 each year, your deductible resets and you start over. If you reach a certain out-of-pocket spending limit during the year, the plan covers most of your drug costs for the rest of that year — this is called catastrophic coverage. The out-of-pocket limit changes each year.

You can change Part D plans once per year during the annual enrollment period. If your current plan no longer covers a drug you need, or if a cheaper plan becomes available, you can switch. You cannot change plans mid-year unless you have a may have access to life event, such as moving to a different state or losing other drug coverage.

Part D and Medigap or Medicare Advantage

If you have Original Medicare plus a Medigap (supplemental insurance) policy, you still need to enroll in Part D separately. Medigap does not include drug coverage. You choose and pay for Part D on your own, and it works alongside your Medigap policy.

If you have Medicare Advantage (Part C) instead of Original Medicare, drug coverage is usually included in your Medicare Advantage plan. You do not enroll in a separate Part D plan. However, some Medicare Advantage plans do not include drug coverage, so check your plan documents or call the plan to confirm.

Questions to Ask Your Doctor or Pharmacist

Before you enroll in a Part D plan, ask your doctor or pharmacist these questions to make sure you choose a plan that works for your medications:

Are there any generic versions of my current medications that work just as well?
If my plan does not cover one of my drugs, what alternative would you recommend?
Do you know which Part D plans in my area cover my medications at the lowest cost?
Will my insurance change affect my current prescriptions or refill schedule?

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 enroll when first may be able to access and later want it, you will owe a late enrollment penalty. The penalty is permanent and increases the longer you wait. If you are certain you will never need prescription drugs, you can skip Part D, but most people find they need medications eventually.

Can I use any pharmacy with my Part D plan?

Most Part D plans have a network of pharmacies where your copays and coinsurance are lowest. You can use pharmacies outside the network, but you will pay more. Check your plan's pharmacy list before you enroll to make sure your preferred pharmacy is included.

What if my Part D plan stops covering a drug I need?

Plans can change their drug lists each year. If your plan removes a drug you take, you can request an exception from the plan, asking them to cover it anyway. If they refuse, you can switch to a different Part D plan during the annual enrollment period that does cover the drug.

Will my Part D premium increase every year?

Part D premiums change annually and vary by plan and location. Some plans increase by a few dollars; others increase more. You can compare plans each year during enrollment and switch to a cheaper option if you find one that still covers your medications.

Can I enroll in Part D after I turn 65?

Yes, but if you enroll after your initial seven-month window, you will owe a late enrollment penalty. The sooner you enroll, the lower your lifetime penalty will be. If you had creditable drug coverage from an employer or other source, you may not owe a penalty — ask your previous plan for proof of coverage.

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.