Medicare Part D, also known as prescription drug coverage, is the part of Medicare that helps you pay for prescription drugs. When you enroll in a Part D plan, you are responsible for paying your deductible, premium, copayment, and coinsurance amounts. The maximum Medicare Part D deductible for 2021 is $445.

Let’s take a closer look at what Medicare Part D is all about and what enrolling in a Medicare Part D plan might cost you in 2021.

Once you are enrolled in Medicare Part A and Part B, original Medicare, you can enroll in Medicare Part D. Medicare prescription drug plans help cover any prescription drugs that are not covered under your original Medicare plan.


The Medicare Part D deductible is the amount that you will pay each year before your Medicare plan pays its portion. Some drug plans charge a $0 yearly deductible, but this amount can vary depending on the provider, your location, and more. The highest deductible amount that any Part D plan can charge in 2021 is $445.


The Medicare Part D premium is the amount you will pay monthly to be enrolled in your prescription drug plan. Like $0 deductibles, some drug plans charge a $0 monthly premium.

The monthly premium for any plan can vary depending on a variety of factors, including your income. If your income is above a certain threshold, you may have to pay an income-related monthly adjustment amount (IRMAA). This adjusted amount for 2021 is based on your 2019 tax return.

Here are the 2021 Part D IRMAAs based on income level as an individual filing on your tax return:

  • $88,000 or less: no additional premium
  • > $88,000 to $111,000: +$12.30 per month
  • > $111,000 to $138,000: +$31.80 per month
  • > $138,000 to $165,000: +$51.20 per month
  • > $165,000 to $499,999: +$70.70 per month
  • $500,000 and above: +$77.10 per month

The thresholds are different for people filing jointly and those who are married and file separately. However, the monthly increase will only ever range from $12.40 to $77.10 extra per month, depending on your income and filing status.

Copays and coinsurance

The Medicare Part D copayment and coinsurance amounts are the costs you pay after your Part D deductible has been met. Depending on the plan you choose, you will either owe copayments or coinsurance fees.

A copayment is a set amount that you pay for each drug, while coinsurance is the percentage of the drug cost that you are responsible for paying.

The Part D copayment and coinsurance amounts can vary depending on the “tier” that each drug is in. The price of each drug within the drug plan’s formulary goes up as the tiers increase.

For example, your prescription drug plan may have the following tier system:

Tier Copayment/coinsurance costTypes of drugs
tier 1lowmostly generic
tier 2mediumpreferred brand-name
tier 3highnonpreferred brand-name
specialty tierhighesthigh-cost brand-name

Most Medicare Part D plans have a coverage gap, also called a “donut hole.” This coverage gap happens when you’ve reached the limit of what your Part D plan will pay for your prescription drugs. This limit is lower than your catastrophic coverage amount, however, which means that you will have a gap in your coverage.

Here’s how the coverage gap for Medicare Part D works in 2021:

  • Yearly deductible. $445 is the maximum deductible that Medicare Part D plans can charge in 2021.
  • Initial coverage. The initial coverage limit for Medicare Part D plans in 2021 is $4,130.
  • Catastrophic coverage. The catastrophic coverage amount kicks in once you have spent $6,550 out of pocket in 2021.

So, what happens when you’re in the coverage gap of your Part D plan? That depends on the following:

Brand-name drugs

Once you hit the coverage gap, you will owe no more than 25 percent of the cost of the brand-name prescription drugs covered by your plan. You pay 25 percent, the manufacturer pays 70 percent, and your plan pays the remaining 5 percent.

Example: If your prescription brand-name drug costs $500, you will pay $125 (plus a dispensing fee). The drug manufacturer and your Part D plan will pay the remaining $375.

Generic drugs

Once you hit the coverage gap, you will owe 25 percent of the cost of the generic drugs covered by your plan. You pay 25 percent and your plan pays the remaining 75 percent.

Example: If your prescription generic drug costs $100, you will pay $25 (plus the dispensing fee). Your Part D plan will pay the remaining $75.

Catastrophic coverage

To make it out of the coverage gap, you must pay a total of $6,550 in out-of-pocket costs. These costs can include:

  • your drug deductible
  • your drug copayments/coinsurance
  • your drug costs in the gap
  • the amount the drug manufacturer pays during the donut hole period

Once you’ve paid this out-of-pocket amount, your catastrophic coverage kicks in. After that, you’ll only be responsible for a minimal copayment or coinsurance. In 2021, the coinsurance amount is 5 percent and the copayment amount is $3.70 for generic drugs and $9.20 for brand-name drugs.

When you enroll in Medicare, you have the option of choosing a Medicare Part D or a Medicare Advantage (Part C) to meet your prescription drug coverage needs.

Medicare Advantage pros and cons

Most Medicare Advantage plans include prescription drug coverage in addition to other coverage options such as dental, vision, hearing, and more. This additional coverage can lead to an increase in overall costs, and you may end up paying more for a Medicare Advantage plan than just adding Part D to your original plan.

In addition, some Medicare Advantage HMO plans may limit your coverage to in-network doctors and pharmacies. This means that your current doctor or pharmacy may not be covered by the Medicare Advantage plan in which you want to enroll.

Late enrollment penalty

No matter whether you choose Medicare Part D or a Medicare Advantage plan, Medicare requires that you have some form of prescription drug coverage. If you go without prescription drug coverage for a period of 63 consecutive days or more after you initially enroll in Medicare, you will be charged a permanent Medicare Part D late enrollment penalty. This penalty fee is added to your prescription drug plan premium each month you are not enrolled.

The Medicare Part D late enrollment penalty is calculated by multiplying the “national base beneficiary premium” by 1 percent and then multiplying that amount by the number of full months you went without coverage. The national base beneficiary premium is $33.06 in 2021, so let’s a look at what this penalty might look like for someone who enrolls late in 2021:

  • Mr. Doe’s initial enrollment period ends on January 31, 2021.
  • Mr. Doe does not enroll in creditable prescription drug coverage until May 1, 2021 (3 months later).
  • Mr. Doe will owe a penalty of $0.33 ($33.06 x 1%) per month that he went without coverage (3 months).
  • Mr. Doe will pay a $1.00 monthly premium penalty ($.33 x 3 = $.99, rounded to the nearest $0.10) going forward.

The late enrollment penalty is subjectto change as the national base beneficiary premium changes each year.

You are eligible to enroll in a Medicare Part D plan during your initial Medicare enrollment period. This period runs 3 months before, the month of, and 3 months after your 65th birthday. There are also additional Medicare Part D enrollment periods, such as:

  • October 15 to December 7. You can sign up if you are already enrolled in parts A and B but have not yet enrolled in Part D, or if you want to switch to another Part D plan.
  • April 1 to June 30. You can sign up if you enrolled in Medicare Part B during the general Part B enrollment period (January 1 to March 31).

Each Medicare Part D plan has a list of prescription drugs that it covers, called a formulary. Prescription drug plan formularies cover both brand-name and generic drugs from the commonly prescribed drug categories. Before you enroll in a Part D plan, check that your medications are covered under the plan’s formulary.

When you enroll in Part D, there are plan fees in addition to your original Medicare costs. These fees include a yearly drug deductible, monthly drug plan premium, drug copayments, and coinsurance.

Medicare beneficiaries who have trouble meeting prescription drug costs may benefit from the Extra Help program. Extra Help is a Medicare Part D program that assists in paying premiums, deductibles, and coinsurance costs associated with your prescription drug plan.

To qualify for Medicare Extra Help, your resources must not exceed a set total amount. Your resources include cash on hand or in the bank, savings, and investments. If you qualify for Extra Help, you can apply through your prescription drug plan with supporting documents, such as an official Medicare notice.

Even if you don’t qualify for Extra Help, you may still qualify for Medicaid. Medicaid provides healthcare coverage for people with low income who are under age 65. However, some Medicare beneficiaries are also eligible for Medicaid coverage, depending on income level. To see if you qualify for Medicaid, visit your local social services office.

Medicare Part D coverage is mandatory as a Medicare beneficiary, so it is important to choose a plan that works for you. When shopping around for prescription drug coverage, consider which of your medications are covered and how much they will cost.

Over time, prescription drug plan costs can add up, so if you are having trouble paying your costs, there are programs that can help.

To compare Medicare Part D or Medicare Advantage (Part C) prescription drug plans near you, visit Medicare’s find a plan tool to learn more.