What Is Medicare Part D?

Medicare Part D provides prescription drug coverage to Medicare beneficiaries. Sometimes referred to as a Medicare PDP (for prescription drug plan), the policies are sold by private insurance companies.

You may add a Part D plan to Original Medicare or to a Medicare Advantage (MA) plan that does not include coverage for prescription drugs. However, most MA plans – around 90 percent – cover prescription medications. When comparing Medicare Advantage plans, the designation MA-PD indicates that the plan includes Part D.

Medicare Part D Requirements

Medicare Part D eligibility includes anyone who is eligible for Original Medicare (Parts A and B). You may enroll in a standalone Part D plan if you have either Medicare Part A or Medicare Part B (or both).

As Part D drug plans are provided by private insurers, you must also meet the plan’s requirements. This usually means living within the Part D plan’s service area.

When Can You Join a Medicare Prescription Drug Plan?

You may only join a Medicare Part D plan during certain enrollment periods.

Initial Enrollment Period (IEP)

Begins 3 months before your 65th birthday and ends 3 months after your birth month. If you sign up for either Part A or Part B – or both – during your IEP, you may also enroll in a prescription drug plan. This period also applies if you were already enrolled in Medicare before turning 65 due to disability or qualifying illness.

Medicare due to a disability

You may enroll in a PDP starting in your 22nd month of getting benefits from either Social Security or the Railroad Retirement Board (RRB). This enrollment period extends for 3 months past your 25th month of disability benefits.

Part B General Enrollment Period

If you don’t have Medicare Part A but enrolled in Part B during the Part B General Enrollment Period (January 1 to March 31), you may sign up for a Part D plan anytime between April 1 and June 30.

Medicare Annual Enrollment Period (AEP)

You may sign up for a Part D plan during the Medicare Annual Enrollment Period (AEP), which lasts from October 15 through December 7.

Medicare Advantage Open Enrollment Period (OEP)

Lasts from January 1 through March 31. If you have an Advantage plan and decide to change to an MA plan that does not include prescription drug coverage OR change back to Original Medicare, you may purchase a Part D plan at this time.

You may also purchase a Part D plan if you qualify for a Special Enrollment Period (SEP). There are literally dozens of ways you may qualify for an SEP. The most common are moving, losing your current coverage, and qualifying for Extra Help. Find the full list on Medicare.gov here.

What Is the Medicare Part D Premium?

Your Medicare Part D out-of-pocket costs typically include a monthly premium, yearly deductible, and either a copayment or coinsurance that you pay at the time of purchase. The amount of your Part D premium varies depending on the plan and provider you choose.

If you collect Social Security benefits, you can have your Part D premium deducted directly from your monthly payment. It typically takes 2 to 3 months before deductions begin. Once they do, your first payment will likely include all skipped payments. Once you’re caught up, Social Security only deducts one payment per month.

You may qualify for Extra Help if your income or resources are limited. This Medicare program helps beneficiaries pay a variety of their out-of-pocket costs for prescription drugs, including the Part D premium.

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What Is the Part D Late Enrollment Penalty?

If you go 63 days or more without Medicare prescription drug coverage (or another type of creditable coverage), you face lifelong penalties.

The Part D late enrollment penalty is 1 percent of the national base beneficiary premium times the number of months you went without prescription drug coverage. That total is then rounded to the nearest dime and added to your monthly premium. The national base beneficiary premium changes every year. In 2022, it is $33.37.

If you went 14 months without Medicare prescription drug coverage, your Part D late enrollment penalty would be $4.70. The calculation looks like this:

$33.37 x 1% x 14 = $4.6718

Rounded to the nearest dime = $4.60

What Drugs Are Covered by Medicare Part D?

Medicare Part D coverage varies according to your plan. When comparing your Part D plan options, look carefully at the drug formulary. This is the list of prescription medications covered by the plan.

In addition to the formulary, most Medicare PDPs use a tier system to help manage drug costs. The tier your medication lands on gives you an idea what it will cost. Most Part D plans use 3 to 5 tiers, with costs rising along with the tier. A 4-tier example may look like this:

Tier 1

Where you find generic prescriptions and the lowest copayment, usually under $10

Tier 2

Have a few non-preferred generic drugs as well as preferred brand name prescriptions drugs, with copays between $20 and $40

Tier 3

Your non-preferred brand name drugs, with copays figured as a percent of the drug’s cost to your plan – expect to pay around 50 percent

Tier 4

Includes specialty drugs and has the highest copayment, typically around 30 percent of the retail cost

The more tiers there are, the lower your copayment usually is on the bottom tiers. For example, a 5-tier plan usually leaves you with copays under $5 for the first tier and under $15 for the second tier.

Medicare Part D Catastrophic Coverage

Catastrophic coverage is the fourth and final phase of Medicare Part D.

You start in the deductible phase. During this time, you pay 100 percent of all costs until you meet your yearly deductible. Again, since private insurance companies provide Part D plans, the yearly deductible varies. However, Medicare does set limit, which may change from year to year. In 2022, the maximum Part D deductible is $480.

Once you meet your yearly deductible, you enter the initial coverage phase, where your share of costs is 25 percent, with your plan making up the other 75 percent. You stay here until you and your plan spend a combined $4,430 (in 2022).

Only around 10 percent of Medicare Part D enrollees advance to the third phase. This is the coverage gap, better known as the donut hole. Your out-of-pocket costs do not change while you’re in the coverage gap – you continue paying 25 percent. But the coverage gap is important because it defines how you reach the catastrophic coverage phase.

Although your out-of-pocket doesn’t change while you’re in the donut hole, cost-sharing for brand name drugs does. It looks like this:

  • You pay 25 percent
  • Your plan pays 5 percent
  • The drug’s manufacturer pays 70 percent

To leave the coverage gap, your out-of-pocket plus the drug manufacturer’s spending must total $7,050. Your monthly premium does NOT count toward entering or leaving the coverage gap.

Once you enter catastrophic coverage, you pay only 5 percent of prescription costs for the rest of the year.

Medicare Tracks Your Spending

Medicare tracks your out-of-pocket spending throughout the year. It may feel Big Brother-ish, but this is why you don’t wind up paying your yearly deductible twice. Even if you move to a new state and have to buy a new plan, Medicare knows you already paid the Part D deductible.

Tracking is also how Medicare knows when you’ve reached the $7,050 out-of-pocket that takes you to the catastrophic coverage phase.

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