When Part D is a separate decision
If you enroll in a Medicare Advantage plan, drug coverage is usually built in and you're done. If you keep Original Medicare — with or without a Medigap policy — then prescriptions are not covered at all until you add a standalone Part D plan, and that's a separate enrollment you make yourself.
The two paths are mutually exclusive in practice: you can't hold a standalone Part D plan alongside most Medicare Advantage plans. Picking one is part of the same decision. Our comparison of the coverage routes lays out the trade-off.
The penalty is the reason not to skip it
People who take no prescriptions often decide to skip Part D and add it later. That decision has a price. The Part D late enrollment penalty is 1% of the national base beneficiary premium for every month you went without creditable drug coverage, it's added to your premium, and it is permanent — it doesn't stop once you've paid it off.
The national base premium is $38.99 a month in 2026, so each year of delay adds roughly $4.70 a month, forever, and the base figure rises over time. A cheap plan now is usually cheaper than the penalty later. Our detailed breakdown of how the Part D penalty is calculated has the arithmetic.
The exception: if you have other drug coverage that Medicare considers creditable — many employer and retiree plans, and VA coverage — no penalty accrues while you have it. Your plan has to tell you in writing each year whether it's creditable. Keep that letter.
Doing it: three places, all free
You can compare and enroll at [medicare.gov/plan-compare](https://www.medicare.gov/plan-compare), which shows every Part D plan in your ZIP code and prices your actual drug list against each. You can enroll on the plan's own website. Or you can use our plan finder, which covers the carriers we're contracted with — fewer plans than Medicare's tool, and we'd rather say so plainly.
Whichever you use, enter your prescriptions first. Sorting Part D plans by premium alone is how people end up on the wrong one; sorting by estimated total yearly cost is the point of the exercise.
Timing
Your first chance is the Initial Enrollment Period — the seven months around your 65th birthday. After that, the annual window is October 15 to December 7, with coverage starting January 1. Special Enrollment Periods open if you lose creditable coverage, move out of the plan's service area, or in a handful of other situations.
A detail people miss: if you're on a Medicare Advantage plan that includes drugs and you join a standalone Part D plan, you'll usually be disenrolled from the Advantage plan and returned to Original Medicare automatically. That's occasionally what someone wants and frequently a shock, so know which one you're doing.
Frequently Asked Questions
Do I need Part D if I don't take any prescriptions?
You're not required to have it, but going without creditable drug coverage builds a permanent late enrollment penalty of 1% of the national base premium per month. Many people take a low-cost plan purely to stop that clock.
Can I have a standalone Part D plan and Medicare Advantage?
Generally no. Joining a standalone Part D plan while on most Medicare Advantage plans will disenroll you from the Advantage plan and return you to Original Medicare.
What counts as creditable drug coverage?
Coverage Medicare considers at least as good as standard Part D — often employer, retiree, or VA drug coverage. The plan must notify you in writing each year whether it's creditable, so keep those letters.
When can I enroll in Part D?
During the seven-month Initial Enrollment Period around your 65th birthday, during October 15 to December 7 each year for a January 1 start, or during a Special Enrollment Period triggered by an event like losing other creditable coverage.
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