Medicare Part D coverage is Medicare’s optional prescription-drug benefit, offered through stand-alone drug plans and Medicare Advantage plans with drug coverage. In simple terms, Part D helps pay for medicines on a plan’s formulary, but beneficiaries may still face premiums, deductibles, copayments, coinsurance, utilization rules, and costs for drugs the plan does not cover. The former “donut hole” coverage gap was eliminated in 2025, when a $2,000 annual out-of-pocket limit began for covered Part D drugs; that limit rises to $2,100 in 2026. Because more than 50 million Medicare beneficiaries use Part D coverage, understanding its phases and remaining gaps is important for budgeting and avoiding unexpected bills.

Medicare Part D Coverage Structure

Medicare Part D coverage is the insurance arrangement that helps pay for outpatient prescription drugs obtained through retail, mail-order, and some specialty pharmacies. Medicare.gov describes Part D as prescription-drug coverage provided by private Medicare-approved plans, rather than as a drug benefit administered directly by traditional Medicare. Each plan sets a premium, formulary, pharmacy network, cost-sharing rules, and utilization requirements within federal standards.

The main Part D plan types are stand-alone Prescription Drug Plans, commonly called PDPs, and Medicare Advantage Prescription Drug plans, commonly called MA-PDs. A beneficiary with Original Medicare may generally select a PDP, while most people enrolled in Medicare Advantage receive drug coverage through their Medicare Advantage plan. Beneficiaries should compare plans annually because formularies, pharmacy networks, premiums, and drug prices can change for the next plan year.

Covered Drugs and Formularies

A formulary is the plan’s approved list of covered prescription drugs. Plans must cover at least two drugs in most therapeutic categories and substantially all drugs in certain protected classes, including medications for cancer, HIV/AIDS, depression, psychosis, and transplant-related conditions. However, one plan may place a drug on a preferred tier while another plan places the same drug on a higher-cost tier or requires additional approval.

Formularies commonly group medicines into tiers. Generic drugs generally have the lowest cost, preferred brand-name drugs may cost more, nonpreferred drugs usually cost still more, and specialty drugs often involve coinsurance. A drug can be technically covered but still create a significant financial burden if it is assigned to a high tier or is subject to coinsurance rather than a fixed copayment.

Pharmacy Networks and Utilization Rules

A pharmacy network identifies the pharmacies where a beneficiary can obtain plan-covered drugs at the plan’s standard cost. Preferred pharmacies may offer lower prices than standard network pharmacies, while out-of-network pharmacies may not be covered except in limited circumstances. Mail-order pharmacies can also offer different quantities or prices for maintenance medications.

Utilization management refers to rules that control how a plan approves payment. Prior authorization requires the prescriber or pharmacy to obtain plan approval before payment. Step therapy requires a beneficiary to try a lower-cost alternative before the plan covers another drug. Quantity limits restrict the amount covered during a specified period. These rules are not the same as a complete coverage exclusion, but they can create a practical gap between having insurance and receiving immediate access to a medicine.

Medicare Part D Payment Phases

Part D payment phases describe how drug costs are divided between the beneficiary, the plan, drug manufacturers, and Medicare. The Inflation Reduction Act substantially changed these phases. The traditional coverage-gap phase, often called the donut hole, ended in 2025. Beneficiaries can still experience changing costs during the year, but the old requirement to pay a larger share after passing an initial coverage limit no longer applies.

Deductible Phase

During the deductible phase, the beneficiary pays the plan’s negotiated price for covered drugs until reaching the annual deductible. The standard maximum deductible is $615 in 2026, although a particular plan may charge less or use a different deductible structure for certain tiers. Some plans do not charge a deductible for lower-cost generic drugs but apply one to brand-name or specialty medicines.

The deductible is separate from the monthly premium. Paying the premium does not satisfy the deductible, and the deductible generally resets at the beginning of each calendar year. Beneficiaries should therefore review January costs even when they stayed with the same plan.

Initial Coverage and Shared Costs

After the deductible, the plan and beneficiary share the cost of covered Part D drugs through copayments or coinsurance. A copayment is a fixed amount, such as a set dollar charge for a preferred generic. Coinsurance is a percentage of the drug’s negotiated price and can be less predictable, particularly for specialty medicines.

The beneficiary’s covered prescription spending accumulates toward the annual Part D out-of-pocket threshold. Generally, premiums do not count toward this threshold, and spending on drugs excluded from Part D does not count either. Manufacturer discounts and other statutory contributions may affect the calculation, so the amount paid at the pharmacy is not always the only factor determining when a beneficiary reaches the limit.

Catastrophic Coverage

Catastrophic coverage begins after a beneficiary reaches the annual out-of-pocket threshold for covered Part D drugs. In 2026, that threshold is $2,100. After reaching it, the beneficiary generally pays no cost sharing for covered Part D drugs for the rest of the calendar year, although the monthly premium continues.

This protection is one of the most significant changes to Part D. Before 2025, beneficiaries could face continuing cost sharing after entering catastrophic coverage. The Centers for Medicare & Medicaid Services explains that the redesigned benefit places a firm annual limit on covered Part D out-of-pocket spending, but it does not make every prescription free or cover every medicine.

Medicare Part D Coverage Gaps

The phrase “coverage gap” now has two meanings. In its historical sense, it referred to the donut hole, which was the former phase in which beneficiaries paid a larger share of prescription costs after passing an initial coverage limit. In everyday use, it can also mean any situation in which a person has Part D but must pay more than expected because of plan rules, exclusions, timing, or eligibility issues.

The Donut Hole Is Closed

The federal Part D redesign eliminated the traditional donut hole beginning in 2025. Beneficiaries now move from the deductible and initial cost-sharing phase directly toward the annual out-of-pocket threshold and then catastrophic coverage. This change is especially important for people taking expensive brand-name or specialty drugs because their covered spending is now limited by a defined annual ceiling.

The end of the donut hole does not mean that beneficiaries pay the same amount all year. Costs may still be highest early in the year while a deductible applies, and a plan may charge different amounts for different tiers. The practical lesson is that the old coverage-gap label should not be used to assume that all prescription costs are predictable or fully covered.

Noncovered Drugs and Excluded Benefits

Part D generally does not cover every medication or every type of prescription-related product. Drugs excluded by federal law may include many medications for weight loss, certain over-the-counter products, fertility treatment, cosmetic purposes, or hair growth. Some medications are covered under Medicare Part B instead of Part D, especially drugs administered in a physician’s office or certain supplies used with durable medical equipment.

If a drug is not covered by Part D, the beneficiary may have to pay the full price, and that spending usually does not count toward the Part D out-of-pocket limit. A prescriber may be able to request a formulary exception when a noncovered drug is medically necessary, but approval is not automatic.

Premiums, Income Adjustments, and Penalties

The Part D premium is another cost that remains outside the annual out-of-pocket limit. Premiums vary by plan and location. Higher-income beneficiaries may also pay an income-related monthly adjustment amount, known as Part D IRMAA, in addition to the plan premium. The Social Security Administration determines this adjustment using federal income information, generally from an earlier tax year.

A late-enrollment penalty can apply when someone goes without Part D or other creditable prescription coverage for 63 days or more after becoming eligible. The penalty is generally calculated from the number of uncovered months and can continue as long as the person has Part D. Employer, union, Veterans Affairs, and other coverage should be checked carefully because not all prescription coverage is considered creditable for Medicare purposes.

Temporary Access and Transition Problems

A beneficiary may experience a temporary coverage gap when changing plans, moving, entering a long-term-care facility, or taking a drug that is newly excluded from a formulary. Medicare rules provide transition supplies in many situations, allowing time for the prescriber and plan to resolve the issue. The beneficiary may still need to request an exception, switch drugs, or file an appeal.

Emergency fills and transition supplies are important safeguards, but they do not guarantee permanent coverage. Beneficiaries should keep records of denial notices, prescription receipts, prescriber communications, and appeal deadlines. Those documents can help establish whether the plan applied its rules correctly.

Medicare Part D Affordability Assistance

Extra Help

Extra Help is the federal Low-Income Subsidy program for people with limited income and resources. Depending on eligibility, it can reduce or eliminate Part D premiums and deductibles and lower the cost of covered prescriptions. The Social Security Administration and Medicare administer related parts of the application and eligibility process.

The Inflation Reduction Act expanded full Extra Help beginning in 2024 by extending assistance to people with incomes up to 150% of the federal poverty level, subject to resource limits. People who qualify for Medicaid, a Medicare Savings Program, or Supplemental Security Income may be enrolled automatically or receive streamlined assistance.

Medicare Prescription Payment Plan

The Medicare Prescription Payment Plan allows eligible Part D enrollees to spread their out-of-pocket prescription costs across monthly payments during the calendar year. It does not lower the total cost of the drugs and does not cover premiums, but it can improve cash-flow management for someone who expects substantial expenses early in the year.

The payment plan is voluntary. A beneficiary should compare the monthly payment obligation with household income and ask the plan for an estimate before enrolling. People with low income should first investigate Extra Help because a subsidy may reduce the underlying cost more effectively than spreading payments.

How to Reduce Medicare Part D Cost Gaps

A simple annual review can identify many avoidable expenses. Medicare’s Plan Compare tool can show estimated yearly costs, premiums, deductibles, pharmacies, and formulary information for available plans. The lowest premium is not necessarily the lowest total cost, especially when a beneficiary uses several brand-name or specialty drugs.

• Prepare a complete list of prescriptions, including dosage and quantity, before comparing plans.
• Check whether each drug is covered and which tier applies.
• Compare preferred pharmacies with standard pharmacies and mail-order options.
• Ask the prescriber whether a covered generic or therapeutic alternative is appropriate.
• Confirm whether prior authorization, step therapy, or quantity limits apply.
• Review Extra Help eligibility and consider the Medicare Prescription Payment Plan if costs are difficult to manage.
• Recheck coverage during Medicare Open Enrollment because plans can change their formularies and prices each year.

Beneficiaries who disagree with a coverage decision can request a redetermination from the plan and pursue additional levels of appeal. A State Health Insurance Assistance Program counselor can provide free, personalized counseling. Pharmacists and prescribers may also help identify an exception request or a lower-cost alternative, but a beneficiary should not stop a medically necessary drug without consulting the prescriber.

Conclusion: Medicare Part D Coverage and Gaps

Medicare Part D coverage is built around formularies, pharmacy networks, deductibles, shared cost phases, and catastrophic protection. The traditional donut hole disappeared in 2025, and the 2026 annual out-of-pocket limit for covered Part D drugs is $2,100. Nevertheless, important gaps remain: premiums are not included in the limit, noncovered drugs may require full payment, utilization rules can delay access, and higher-income beneficiaries may owe additional charges.

The most effective response is active plan management. Beneficiaries should compare total annual costs rather than premiums alone, verify formulary status and pharmacy networks, investigate Extra Help, and use appeals when a plan denies an appropriate medicine. For further guidance, consult Medicare.gov, a State Health Insurance Assistance Program counselor, the plan’s evidence of coverage, or a qualified benefits adviser before making coverage decisions.

Sources: Centers for Medicare & Medicaid Services, Medicare Part D Improvements, https://www.cms.gov/inflation-reduction-act-and-medicare/part-d-improvements; Medicare.gov, Costs for Medicare Drug Coverage, https://www.medicare.gov/drug-coverage-part-d/costs-for-medicare-drug-coverage; Centers for Medicare & Medicaid Services, Calendar Year 2026 Announcement for the Medicare Advantage and Part D Prescription Drug Programs, https://www.cms.gov/newsroom/fact-sheets/calendar-year-2026-announcement-medicare-advantage-and-part-d-prescription-drug-programs; Medicare.gov, Medicare Prescription Payment Plan, https://www.medicare.gov/prescription-payment-plan; Social Security Administration, Medicare Part D Extra Help Program, https://www.ssa.gov/medicare/part-d-extra-help; Medicare.gov, How to Get Prescription Drug Coverage, https://www.medicare.gov/drug-coverage-part-d