Part D is the prescription drug coverage piece of Medicare. It looks simple from the outside and gets confusing fast — formularies, tiers, deductibles, late enrollment penalties that follow you for life. Here's what actually matters and how to think about it.
Part D is the prescription drug part of Medicare. It's separate from Part A (hospital), Part B (medical), and Medigap — the supplement plan some people buy to fill in the gaps Original Medicare leaves behind. None of those cover your retail prescriptions. Part D does.
You get Part D one of two ways. Either you buy a stand-alone Part D plan that pairs with Original Medicare, or you enroll in a Medicare Advantage plan that has prescription drug coverage built in. Most people on Original Medicare with a Medigap plan also have a stand-alone Part D plan running alongside both of them — three pieces working together.
Part D plans are sold by private insurance companies approved by Medicare. The plans follow federal rules, but each carrier decides which specific medications are on their list, what tier each medication is in, and how much you pay for it. That's why two Part D plans with similar premiums can give you wildly different experiences depending on what prescriptions you actually take.
This is the part of Medicare where most people make a mistake just by guessing. A licensed agent can compare plans against your actual prescription list in about ten minutes. It's free.
Talk to an agentHere's the part of Part D nobody warns people about until it's too late. We're going to tell you up front.
Part D is technically optional. You don't have to enroll. But if you don't enroll when you're first eligible — and you don't have other prescription drug coverage that Medicare considers "creditable" — you can be hit with a late enrollment penalty when you finally do enroll later.
That penalty isn't a one-time fee. It gets permanently added to your Part D premium. Every month. For the rest of your life on Medicare. The longer you went without coverage, the bigger the penalty. People who skip Part D for a few years thinking "I don't take any prescriptions right now" can end up paying significantly more for the rest of their lives once they finally need a plan.
There are exceptions. If you have prescription drug coverage through an employer plan, the VA, or another source that meets Medicare's definition of "creditable coverage," that counts. You won't get penalized for skipping Part D while you have it. But the moment that coverage ends, you have a 63-day window to enroll in a Part D plan. Miss the window, and the penalty clock starts running.
This is the single biggest reason we tell people approaching 65 to talk to an agent before their initial enrollment window closes — even if they take zero prescriptions today.
Part D plans have a few moving parts. Once you understand them, comparing plans gets a lot easier.
The formulary is the plan's list of covered medications. Every plan has its own. A medication that's covered on one plan might not be covered on another, or might be on a more expensive tier. This is why we always tell people: never enroll in a Part D plan without first checking that your specific prescriptions are on the formulary. We do this for you when we run a comparison.
Plans organize their formularies into tiers — usually four or five. Lower tiers are generally generic medications and cost less per fill. Higher tiers tend to be brand-name and specialty medications and cost more. Two plans can both cover your medication but put it on different tiers, which means very different costs to you over a year.
Some plans add rules to certain medications even when they're on the formulary. The most common ones are prior authorization (your doctor has to get the plan's approval before you can fill it), quantity limits (the plan caps how much you can get at once), and step therapy (the plan requires you to try a less expensive medication first). These rules can be a real headache at the pharmacy counter if you don't know about them up front.
Part D used to have four cost phases including a "coverage gap" most people called the donut hole. That phase was eliminated in 2025. The structure now is simpler.
If your plan has an annual deductible, you pay full price for your covered medications until you've met it. Some plans waive the deductible entirely. Some apply it only to certain tiers.
After you meet the deductible, you pay just the copay or coinsurance for each prescription based on which tier it's in. You stay here until your total out-of-pocket spending hits a federal cap.
Once you hit the annual out-of-pocket cap, you don't pay anything for your covered medications for the rest of the calendar year. This cap was one of the biggest changes in recent Medicare legislation.
Everything resets January 1. New year, clean slate.
Trying to figure out which Part D plan would actually save you money on your specific prescriptions? That's exactly what a comparison call does. No charge.
Get a free comparisonWhen people ask how to pick a Part D plan, the honest answer is: don't pick by premium alone. The cheapest plan on paper can be the most expensive in real life if it doesn't cover your medications well. Here's what actually matters.
This is the first question. Not "does the plan cover most things" — does it cover your medications. Always check before enrolling.
A medication can be on one plan's formulary at a low tier and on another at a high tier. Same drug, very different cost over a year.
If your plan requires prior authorization or step therapy on a medication you take, that's a friction point you'll deal with every refill.
Plans handle deductibles differently. Some waive them. Some apply them only to certain tiers. Some hit you with the full deductible on day one.
Most plans have preferred pharmacies where your costs are lower. If your pharmacy isn't in the preferred network, that adds up over a year.
Premium + deductible + copays + coinsurance over a full year on your specific prescriptions. That's the number we run for you.
The 7-month window around your 65th birthday — three months before, the month of, and three months after. This is when most people first enroll in Part D. Missing this window without other creditable coverage starts the late enrollment penalty clock.
October 15 through December 7 every year. During this window, you can switch Part D plans, switch Medicare Advantage plans, or move between Original Medicare and Medicare Advantage. Changes take effect January 1.
Triggered by life events — moving to a new area, losing creditable drug coverage from another source, qualifying for assistance programs, and others. SEPs give you a window to enroll or switch outside the standard windows.
Every September, your Part D carrier sends you an Annual Notice of Change — a booklet showing exactly how your plan is changing for the next year. Premium changes, formulary changes, tier changes, new utilization rules. Most people don't read it. They should. The plan that fit you this year might not fit you next year, and AEP is when you do something about it.
Not sure which window applies to you? That's one of the first things a licensed agent can clear up. It's a quick conversation.
Talk to an agentThat's the cue to do a Part D review. We do them for free during AEP every year.
Talk to an agentNo hard sell. Three steps and a real conversation.
Your medications, dosages, and the pharmacy you usually use. That's most of what we need to run a real comparison.
A licensed agent runs your medications through Part D plans in your area — checking formularies, tiers, utilization rules, and total annual spending — and shows you the strongest matches.
You pick what fits. We handle the paperwork, and we run a fresh comparison for you every fall during AEP — because Part D plans change every year.
It costs you nothing. We're paid by the carrier you enroll with. Your premium is the same whether you enroll through us, through the carrier directly, or through anyone else.
Tell us a bit about your situation and a licensed agent will reach out within one business day. Bring your prescription list and we'll compare plans for you. No pressure to enroll in anything.
This is the part of Medicare where guessing costs people the most money — either through a permanent late enrollment penalty or through a plan that doesn't cover their medications well. A free comparison call clears it up in minutes.
By calling the number above, you will be connected to a licensed insurance agent. Mon–Fri 8am–8pm CT.
