Medicare Part D Plans

Medicare Part D provides prescription drug coverage for Medicare enrollees. Part D plans are offered by private insurers, not the federal government.

Part D is optional coverage that works with many other forms of insurance, including Original Medicare, Medicaid, employer health plans, and, in some cases, Medicare Advantage plans.

Each Part D prescription drug plan may have varying benefits, costs, and rules.

You can compare Part D plans available where you live and enroll in a Medicare prescription drug plan online in as little as 10 minutes when you visit

Enroll in Medicare Part D at


Who is eligible for Part D plans?

About 20.6 million people were enrolled in stand-alone Medicare Part D plans in 2019.2

In order to qualify for Medicare Part D coverage, you first must be enrolled in Medicare Part A and/or Part B.

Once you are eligible, you need to apply during a Part D enrollment period. If you do not sign up for a Part D plan when you are first eligible and you do not have creditable coverage, you may be required to pay a monthly late enrollment penalty once you do enroll.

If you already have a Medicare Advantage plan, you may not be eligible for a Part D plan, depending on the type of plan you are enrolled in.

If you have a Medicare Advantage plan with drug coverage, you can't add a standalone prescription drug plan.

When can I enroll in a Part D plan?

Medicare Part D enrollment periods
Enrollment period Dates What you can do during this period
Initial Enrollment Period (IEP) Starts 3 months before the month you turn 65
Ends 3 months after the month you turn 65
Sign up for a Medicare Part D plan
Medicare Open Enrollment Period (aka the Annual Enrollment Period, or AEP) Starts October 15
Ends December 7
- Sign up for a Medicare Part D plan
- Switch Medicare Part D plans
- Leave a Medicare Part D plan
Special Enrollment Period (SEP) Depends on your personal situation Depends on your personal situation

You must wait for an enrollment period to sign up for, make changes to, or leave a Medicare Part D plan.

Initial Enrollment Period

Each beneficiary is granted an Initial Enrollment Period (IEP) when they first become eligible for Medicare.

This seven-month period begins three months before you turn 65 years old, includes the month of your birthday and continues for three additional months.

During your IEP, you may sign up for a Medicare Part D plan or a Medicare Advantage plan. 

Medicare Open Enrollment Period for Medicare Advantage and prescription drug coverage

Also called the Annual Enrollment Period (AEP), this period takes place every year between October 15 and December 7.

During AEP, you may:

  • Enroll in a Medicare Part D plan
  • Switch from one Part D plan to another
  • Disenroll in a Part D plan
  • Enroll in a Medicare Advantage plan
  • Switch from one Medicare Advantage plan to another
  • Disenroll from a Medicare Advantage plan

Special Enrollment Period

A Special Enrollment Period (SEP) may be granted at anytime throughout the year for people who have specific qualifying circumstances.

These qualifying situations include, but are not limited to:

  • Losing creditable drug coverage through no fault of your own
  • Moving outside of your drug plan’s service area
  • Experiencing contract or enrollment errors or violations
  • Moving into or out of a skilled nursing facility or nursing home
  • Gaining or losing eligibility for a Special Needs Plan

A licensed insurance agent can help you find out if you qualify for a Special Enrollment Period. Depending on your qualifying circumstance, you may or may not be eligible to enroll in a Part D plan during a certain Special Enrollment Period.

Five-Star Special Enrollment Period

Each year, the Centers for Medicare and Medicaid Services (CMS) rates all Medicare Part D and Medicare Advantage plans on a set of criteria and assigns a rating between one and five stars, with five being the highest rating.3

The Five-Star Enrollment Period runs each year from December 8 to November 30 of the following year.

Any beneficiary who is a member of a Part D or Medicare Advantage plan that does not hold a five-star rating may use this enrollment period to enroll in a plan that has a five-star rating.

You can only enroll in a five-star plan if one is available where you live.

What is the Part D late enrollment penalty?

If you need prescription drug coverage, it is important to enroll in a Part D plan during your Initial Enrollment Period or when you are first eligible. If not, you may face a late penalty.

If your IEP ends and there is a period of 63 days or more in a row when you do not have creditable prescription drug coverage, you may have a late enrollment penalty added to your monthly premium for as long as you have Medicare prescription drug coverage.

Drug coverage is creditable if it pays – on average – at least as much as the standard Medicare prescription drug coverage.

What does Medicare Part D cover?

Part D plans have different formularies, tiers, coverage rules, and pharmacy networks.

Coverage rules such as quantity limits, prior authorization, and step therapy may limit how and when you receive your prescription drugs.

Part D plans also may have pharmacy networks, which may impact the cost of your prescription drugs.

More info: Part D benefits

How much do Part D plans cost?

Medicare Part D prescription drug plans don't pay for everything.

If you have a Part D plan, you may have to pay premiums, "donut hole" drug costs, and other out-of-pocket costs like deductibles and copayments.

More info: Part D costs - Premiums, deductibles, and the donut hole

How do I compare Medicare prescription drug plans?

There are many Part D plans to choose from. In 2020, there are 948 plans offered across 34 regions nationwide (excluding U.S. territories).2

You should make sure to compare the following 3 factors when choosing your Part D plan:

  • Benefits
  • Costs
  • Star ratings3

Our online plan comparison tool can help you easily evaluate all of these factors for available plans in your area offered through this website.

Compare Medicare prescription drug plans

Compare Plans

Or call TTY Users: 711 24/7 to speak with a licensed insurance agent.

Medicare Part D plans by state

Medicare Advantage plans and Medicare Part D plans are both offered by private insurance companies, and plan availability varies from state to state. Learn more about Medicare Part D plan enrollment nationwide and in your state.

You can also find more Medicare prescription drug coverage information and resources for your state.

More info: Medicare Part D plans by state

What is a Medicare formulary?

A Medicare formulary is the list of prescription drugs that are covered by a particular Medicare Part D or Medicare Advantage plan.

Each plan includes its own formulary that determines which drugs are covered by the plan and how much the drugs cost based on which tier the drug is classified into.

Drugs on a Medicare formulary are divided into tiers that determine the cost paid by beneficiaries.

For example, a tier 1 drug might consist of low-cost, generic drugs and require only a small copayment in order to fill a prescription. A tier 4 drug, however, might be a more expensive name brand drug that requires a higher copayment.

The number of drug tiers and the cost breakdown will vary according to each plan.

Drugs may be added or removed from the market at any time, and therefore drugs may be added or removed from a plan’s formulary. Drugs may also remain for sale on the market but be removed from a plan’s formulary for a variety of reasons.

Beneficiaries reserve the right to request that a Medicare plan cover a particular drug. You can also request to pay a lower amount for a covered drug.

All Medicare formularies generally must include coverage for at least two different drugs within most drug categories, and they must include all available drugs for the following categories:

  • HIV/AIDS treatments
  • Antidepressants
  • Antipsychotic medications
  • Anticonvulsive medications to treat seizure disorders
  • Immunosuppressants
  • Anticancer drugs not covered by Medicare Part B

A Medicare formulary won’t include over-the-counter drugs or weight-loss drugs.

Some drugs on a Medicare formulary come with certain types of restrictions, such as:

  • Prior authorization
    Beneficiaries may be required to show that they meet certain criteria for consuming the particular drug.

  • Step therapy
    Beneficiaries must first try a less-expensive form of a drug that has been proven effective before being covered for the more expensive version.

  • Quantity limits
    There may be a restriction on the dosage amount of a drug or the frequency that the prescription may be filled.

  • Opioid safety limits
    Opioids often contain restrictions for coverage, and doctors will usually work with a beneficiary and a pharmacist to determine a safe level of opioid prescription for each patient.

Find a Medicare plan that offers the prescription drugs you need

You may be able to find Medicare plan options in your area that feature a drug formulary that fits your prescription drug coverage needs.

To compare plans where you live, call to speak with a licensed insurance agent.

Compare Medicare prescription drug plans

Compare Plans

Or call TTY Users: 711 24/7 to speak with a licensed insurance agent.