What is Medicare Part D?
Medicare Part D is prescription drug coverage offered through Medicare-approved private insurance companies. You can get it through a standalone drug plan with Original Medicare or through many Medicare Advantage plans.
Standalone Drug Plan
Works alongside Original Medicare and is commonly paired with a Medicare Supplement policy.
Medicare Advantage
Many Medicare Advantage plans include Part D coverage in the same plan, though benefits and rules vary.
Coverage Is Plan-Specific
Each plan has its own covered-drug list, pharmacy network, cost sharing, and medication-management rules.
When can you enroll?
You may be able to enroll when you first become eligible for Medicare, during an applicable annual enrollment period, or when you qualify for a Special Enrollment Period. The correct timing depends on your situation and current coverage.
Your costs can change as you move through the calendar year.
The amounts below describe the 2026 defined standard Part D benefit. Your plan may charge a smaller deductible, cover certain drugs before the deductible, or use copays and coinsurance that differ from the standard design.
Annual Deductible
Up to $615 in 2026
Under the standard benefit, you pay the full negotiated cost of covered prescriptions until the deductible is met. Some plans have a lower or $0 deductible, and some drug tiers may be covered before it is met.
Initial Coverage
Standard cost sharing: 25%
After the deductible, you pay your plan’s copay or coinsurance for covered drugs. The defined standard benefit uses 25% coinsurance. This phase continues until your qualifying out-of-pocket spending reaches $2,100 in 2026.
Catastrophic Coverage
$0 for covered Part D drugs
Once qualifying out-of-pocket spending reaches the $2,100 threshold, you pay no cost sharing for covered Part D drugs for the rest of the calendar year.
Lower tiers generally cost less, but every plan organizes its formulary differently.
A formulary is a plan’s list of covered drugs. Plans group those drugs into cost levels called tiers. The examples below are common, but your plan may use different names, a different number of tiers, or different copays and coinsurance.
Tier 1 · Preferred Generics
Usually includes common, lower-cost generic medications and typically has the plan’s lowest copays.
Tier 2 · Generics Or Preferred Brands
May include non-preferred generics or brand-name drugs the plan prefers. Costs are generally higher than Tier 1 but lower than non-preferred brands.
Tier 3 · Non-Preferred Brands
Often includes brand-name drugs when the plan prefers a lower-cost alternative. These medications generally have higher copays or coinsurance.
Specialty Tier · High-Cost Drugs
Often includes high-cost medications such as certain biologics, injectables, or specialty drugs. Cost sharing is commonly a percentage of the drug’s price.
Additional Plan-Specific Tiers
Some plans add tiers for preferred specialty drugs, high-cost non-specialty medications, select insulin, vaccines, or other preventive drugs. Review the plan formulary for the exact structure.
A Tier Exception May Be Available
If your prescriber believes you need a higher-tier drug, you may be able to ask the plan to cover it at a lower cost-sharing level. Approval is not automatic.
Some covered prescriptions require an extra step before the plan will pay.
Prior Authorization
You or your prescriber must get approval from the plan before it will cover certain medications. The prescriber may need to show that the drug is medically necessary and that the plan’s requirements are met.
Step Therapy
The plan may require you to try a lower-cost drug that is generally effective for your condition before it covers a more expensive medication. You or your prescriber may request an exception when medically appropriate.
Quantity Limits
The plan may limit how much medication it covers during a certain period, such as a specific number of tablets per month. Your prescriber may request an exception if the limit is not appropriate for your condition.
Coverage rules are plan-specific. Check the formulary and contact the plan or your prescriber before filling a prescription that has a restriction.
Review Medicare Drug Plan Rules(opens in new tab)
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Send a MessagePart D FAQs
Common questions about how prescription coverage works.
A formulary is the plan's list of covered drugs. Formularies can differ by plan and can change, so check every prescription by exact name, dose, and form before selecting or renewing coverage.
Tiers group covered drugs by cost-sharing. Preferred generics are often on lower-cost tiers, while non-preferred or specialty drugs may cost more. Each plan sets its own tier structure and copay or coinsurance amounts.
These are plan rules that may require approval before coverage, trying another drug first, or limiting how much is covered at one time. Your prescriber can help with exceptions or supporting information when appropriate.
Part D can include an annual deductible, an initial coverage stage, and catastrophic coverage after your covered out-of-pocket spending reaches the year's limit. Current costs are set annually and plan details still vary.
Plans negotiate different pricing and may identify preferred and standard network pharmacies. Your cost can also depend on the drug's tier, quantity, refill timing, and whether mail order is available.
No. Each plan has its own formulary, tiers, pharmacy network, and coverage rules. Two plans with similar premiums can produce very different yearly costs for the same medication list.
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