Glossary
Medicare Part D
Medicare's optional prescription drug coverage — almost always unnecessary if you have TRICARE For Life.
Also known as: Drug Plan, PDP, Prescription Drug Plan, Part D
What is it?
Part D is voluntary outpatient prescription drug coverage offered by private insurers under contract with Medicare. It has its own monthly premium, deductible, and tiered formulary.
Why does it matter?
For retired military, Part D is usually a mistake. The TRICARE Pharmacy Program (administered by Express Scripts) is **creditable coverage** — meaning it's considered as good as or better than Part D. You do not need Part D, and signing up can disrupt your TRICARE pharmacy benefits.
When you'll encounter it
You'd encounter Part D when comparing standalone drug plans (PDPs) or when an MA plan bundles drug coverage (MAPD). On TFL, the only time you'd seriously consider Part D is if a specific MA-PD plan offers it as part of the package.
Impact on Medicare
Part D is administered by private plans, not Medicare directly. It has a coverage gap ('donut hole') structure that resets annually.
Impact on TRICARE For Life
TFL beneficiaries should generally NOT enroll in a standalone Part D plan. TRICARE Pharmacy already covers your prescriptions through MTF, home delivery, network, and non-network channels.
Impact on Medicare Advantage
Many MA plans for veterans are MA-PD (include Part D drug coverage). You can use both the MA plan's drug benefits and TRICARE Pharmacy without losing either.
Common misconceptions
- "I have to enroll in Part D at 65 or pay a penalty." — Not if you have TRICARE. TRICARE Pharmacy is certified as creditable coverage, so no late-enrollment penalty applies.
Related lessons
Related glossary terms
Related questions
Official sources
Last reviewed January 2026 against the 2026 Medicare & You and TRICARE For Life handbooks.