How Medicare Covers Prescription Drugs: What Part B, Part D, and Discounts Mean for Your Costs

Prescription drugs can be one of the most confusing parts of Medicare. Many retirees assume that once they enroll in Medicare, their medications will automatically be covered. But the reality is far more complex.

Different medications fall under different parts of Medicare, and some drugs may not be covered at all.

Understanding how Medicare handles prescription coverage and how to reduce costs when coverage falls short can make a significant difference in your healthcare expenses during retirement.

The New Medicare Prescription Drug Spending Cap

One of the biggest recent changes to Medicare prescription coverage involves the introduction of a spending cap for Medicare Part D drug plans.

Beginning in 2025, Medicare limited annual out-of-pocket prescription drug costs to $2,000. That cap increased slightly to $2,100 this year.

For many retirees, this change provides meaningful protection against extremely high drug costs.

However, there are important limitations.

The spending cap does not automatically apply to every medication. Certain situations may fall outside the cap, including:

• Newly released medications
• Drugs not listed on a plan’s formulary
• Situations where patients cannot afford required out-of-pocket costs

Because of these restrictions, some retirees still encounter expensive medications despite the new cap.

Understanding the Difference Between Medicare Part B and Part D

Medicare prescription drugs are generally covered through two different programs.

Medicare Part D

Part D plans cover most retail prescription medications, including:

• blood pressure medications
• cholesterol drugs
• diabetes medications
• inhalers and other self-administered treatments

These drugs are typically purchased at pharmacies and paid for through prescription drug plans.

Each Part D plan maintains its own formulary, which is a list of medications it covers. If a drug is not on that list, coverage may be limited or unavailable.

Medicare Part B

Part B covers medications that are administered in clinical settings or involve specialized equipment.

Examples include:

• infusion medications
• injectable biologics
• medications administered in outpatient clinics
• certain inhaled medications delivered through a nebulizer
• insulin delivered through an insulin pump

In many cases, Part B can be significantly cheaper than Part D when paired with a Medicare Supplement plan.

Part B typically covers 80 percent of costs, while supplemental plans such as Plan G or Plan N can cover the remaining balance after the annual deductible.

Vaccines Covered by Medicare

Vaccines are also split between Medicare coverage categories.

Covered by Part B:

• Flu vaccine
• Pneumonia vaccine
• Hepatitis B vaccine
• COVID-19 vaccines

Covered by Part D:

• Shingles vaccine
• RSV vaccine
• Tdap vaccine

Understanding which part of Medicare covers a vaccine helps avoid unexpected pharmacy bills.

What Happens When a Drug Isn’t Covered

Sometimes Medicare plans refuse coverage for certain medications.

This can happen when:

• the medication is new
• the drug is not listed on the formulary
• the plan requires additional medical justification

Fortunately, beneficiaries still have options.

Requesting a Formulary Exception

Doctors can request a formulary exception when a medication is medically necessary but not listed on a plan’s approved drug list.

If approved, the plan may cover the medication despite its absence from the standard formulary.

Switching Plans During Open Enrollment

Medicare beneficiaries can also change drug plans during Medicare Open Enrollment, which runs October 15 through December 7 each year.

Any changes take effect January 1 of the following year, allowing beneficiaries to select a plan that better covers their medications.

Paying Cash Can Sometimes Be Cheaper

In some cases, the most affordable option may be paying cash for prescriptions rather than using Medicare coverage.

Several discount platforms allow consumers to compare drug prices across pharmacies.

Popular options include:

• GoodRx
• SingleCare
• Amazon Pharmacy

These services can dramatically reduce the cost of medications, sometimes lowering prices by hundreds of dollars.

For example, a medication with a retail price of $1,056 may be available for roughly $79 per month through manufacturer discounts after an initial free prescription fill.

Manufacturer Discount Programs

Drug manufacturers often offer direct discount programs for patients.

These programs can include:

• free introductory prescriptions
• reduced monthly pricing
• assistance programs for high-cost medications

While not every drug qualifies, these programs can provide substantial savings when Medicare coverage is limited.

Alternative Prescription Coverage Options

Not everyone needs to enroll in a Medicare Part D plan.

Some retirees have “credible coverage” through other programs, including:

• employer-sponsored health plans
• union healthcare benefits
• VA healthcare coverage
• Tricare for Life
• federal employee health benefits

These programs provide prescription drug coverage comparable to Medicare Part D.

As long as coverage is considered credible, beneficiaries can avoid late enrollment penalties.

Why Understanding Medicare Drug Coverage Matters

Prescription costs can add up quickly during retirement.

Without proper planning, some retirees may spend thousands of dollars each year on medications.

Understanding how Medicare Parts B and D work and knowing when alternative options like discounts or plan changes make sense can help reduce those costs significantly.

Healthcare expenses are one of the largest financial risks retirees face. Learning how prescription coverage works is one of the most effective ways to protect both your health and your retirement budget.