Choosing Medicare prescription drug coverage can look simple at first.
You find a Medicare Part D plan, look at the monthly premium, and enroll.
But that can be one of the biggest mistakes people make when choosing Medicare drug coverage.
A plan with a very low monthly premium may not be the least expensive plan for your prescriptions. The medications you take, their dosages, the plan’s formulary, drug tiers, pharmacy network, coverage rules, deductible and copayments can all affect what you actually spend during the year.
That’s why I tell my clients not to ask:
“Which Part D plan is the cheapest?”
A better question is:
“Which Part D plan is the most cost-effective for the prescriptions I actually take?”
Those are two very different questions.
In this guide, I’ll explain how Medicare Part D works, what it may cost in 2026, how formularies and drug tiers affect your prescriptions, why your pharmacy matters, and some of the mistakes to avoid when choosing prescription drug coverage.
What Is Medicare Part D?
Medicare Part D is Medicare prescription drug coverage.
It helps pay for covered prescription medications, including both brand-name and generic drugs.
Part D coverage is offered through private insurance companies approved by Medicare. Because different plans can have different premiums, formularies, pharmacy networks and cost-sharing, two Part D plans available in the same area can work very differently for the same person.
If you have Original Medicare, you can generally get prescription drug coverage by enrolling in a stand-alone Medicare Part D prescription drug plan.
If you have Medicare Advantage, prescription drug coverage is included in many Medicare Advantage plans.
Quick Answer
Medicare Part D helps cover prescription drugs, but there is no single Part D plan that is automatically best for everyone.
The right plan can depend heavily on:
- The prescriptions you take
- Your medication dosages
- Whether your medications are on the plan’s formulary
- Which drug tiers your medications are placed in
- Your preferred pharmacy
- The plan’s deductible
- Copayments or coinsurance
- Coverage restrictions
- Your estimated total annual prescription costs
That is why comparing Part D plans should be personal.
Why the Cheapest Part D Premium May Not Be the Cheapest Plan
This is one of the most important things to understand about Medicare Part D.
Imagine you are comparing two plans.
One has a very low monthly premium.
The other costs a little more each month.
At first glance, the lower-premium plan may seem like the obvious choice.
But what happens if one of your medications is on a higher drug tier under that plan?
What if your pharmacy is not a preferred pharmacy?
What if one of your prescriptions requires prior authorization?
Or what if a medication you regularly take is not on the plan’s formulary at all?
Suddenly, the plan that looked cheaper may not be cheaper anymore.
From My Office
When I help someone compare Medicare prescription drug coverage, I don’t want to know only what they’re paying for the plan.
I want to know what medications they actually take.
That includes the medication name, dosage, how often it is taken and where they prefer to fill their prescriptions.
Those details matter.
I would rather help someone evaluate the whole year’s potential costs than choose a plan simply because its monthly premium looked attractive.
What Is a Part D Formulary?
One Medicare term that every beneficiary should understand is formulary.
A formulary is simply the list of prescription drugs a Medicare drug plan covers.
Every Part D plan has its own formulary.
That means a medication covered by one plan may be handled differently by another plan.
Medicare requires drug plans to cover a wide range of medications, and plans must cover most drugs in certain protected classes. However, that does not mean every Part D plan covers every prescription in exactly the same way.
Before choosing a plan, check each prescription you take against that plan’s current formulary.
What If My Prescription Isn’t on the Formulary?
Don’t automatically assume you have no options.
Depending on the situation, you and your prescriber may be able to request a coverage exception. Your doctor or other prescriber generally needs to provide medical support explaining why the requested medication is medically necessary.
But this is exactly why checking your medications before enrolling is so important.
You don’t want to discover at the pharmacy counter that a medication you rely on isn’t covered the way you expected.
How Medicare Part D Drug Tiers Can Affect What You Pay
Many Part D plans divide covered medications into different levels called tiers.
Generally, medications on lower tiers have lower cost-sharing, while medications on higher tiers can cost more.
A plan might structure its tiers to include categories such as:
- Preferred generic drugs
- Generic drugs
- Preferred brand-name drugs
- Non-preferred drugs
- Specialty drugs
The exact structure varies by plan.
So simply asking whether a drug is covered isn’t always enough.
You also want to ask:
“What tier is my medication on, and what will I pay for it?”
Aja’s Medicare Tip
When comparing prescription drug plans, don’t stop when you see a checkmark showing that your medication is covered.
Look deeper.
Check the tier, cost-sharing and coverage rules attached to that prescription.
That’s where some of the biggest differences between Part D plans can appear.
Your Pharmacy Can Change What You Pay
Here’s another Part D detail that surprises people:
The pharmacy you use can affect the price you pay for your prescriptions.
Medicare drug plans contract with networks of pharmacies. Some plans also designate certain pharmacies as preferred in-network pharmacies.
Using a preferred pharmacy may result in lower copayments or coinsurance for certain medications than using another pharmacy in the same plan’s network.
That’s why someone can choose a Part D plan that appears to cover all of their medications and still end up paying more than expected.
The prescriptions may not be the problem.
The pharmacy may be.
Don’t Automatically Assume Your Current Pharmacy Is the Best Choice
If you have used the same pharmacy for years, you may understandably want to keep using it.
But before choosing a Part D plan, check:
- Is the pharmacy in the plan’s network?
- Is it a preferred pharmacy?
- Would another nearby preferred pharmacy lower your prescription costs?
- Does the plan offer mail-order options for medications you take regularly?
Convenience matters.
But so does knowing what that convenience may cost you.
What Does Medicare Part D Cost in 2026?
There is no single price for Medicare Part D.
Your costs can depend on the plan you choose, the prescriptions you take, the pharmacy you use and how the plan covers your medications.
Part D costs may include:
- A monthly plan premium
- An annual deductible
- Copayments
- Coinsurance
- Costs associated with the specific drugs you take
In 2026, the maximum deductible a Part D plan can charge is $615. Some plans may have a lower deductible or no deductible, and a plan may apply its deductible differently depending on the drugs involved.
But one of the biggest changes to Medicare prescription drug coverage in recent years is the annual limit on out-of-pocket spending for covered Part D drugs.
The $2,100 Medicare Part D Out-of-Pocket Cap in 2026
In 2026, people with Medicare Part D have a $2,100 annual out-of-pocket cap for covered Part D drugs.
Once your applicable out-of-pocket spending reaches that amount, you generally won’t pay additional out-of-pocket costs for covered Part D drugs for the remainder of the calendar year.
This protection can be particularly important for people who take expensive medications.
But there is an important detail that can easily be misunderstood.
The $2,100 Cap Does Not Mean Every Prescription Is Automatically Covered
The out-of-pocket cap applies to covered Part D drugs.
It does not mean you can fill any prescription medication and automatically have it count toward the $2,100 limit.
Your plan’s formulary and coverage rules still matter.
That’s another reason I emphasize checking your prescriptions before choosing a plan.
A strong out-of-pocket protection doesn’t eliminate the need to understand what your particular plan covers.
Aja’s Medicare Tip
Don’t choose a Part D plan simply because Medicare now has an annual out-of-pocket cap.
The cap provides important financial protection, but your goal should still be to find coverage that works well before you ever get close to that limit.
Look at your medications, pharmacy and estimated yearly costs together.
How Medicare Part D Coverage Works in 2026
Part D used to be commonly explained using several coverage stages, including the infamous “donut hole.”
That old explanation is no longer the best way to understand today’s Part D benefit.
Under the redesigned Part D benefit, the coverage gap phase has been eliminated.
For 2026, it’s more useful to think about Part D in three stages:
1. The Deductible Stage
Depending on your plan, you may need to pay a deductible before the plan begins paying its share for certain covered medications.
The maximum Part D deductible in 2026 is $615, although individual plans can charge less.
2. The Initial Coverage Stage
After the applicable deductible, you generally pay the copayment or coinsurance required by your plan for covered prescriptions.
How much you pay can depend on factors such as the medication’s tier and the pharmacy you use.
3. The Catastrophic Coverage Stage
Once your applicable annual out-of-pocket spending for covered Part D drugs reaches $2,100 in 2026, you enter catastrophic coverage.
At that point, you generally pay $0 for covered Part D drugs for the rest of the calendar year.
What Happened to the Medicare Part D Donut Hole?
If you’ve had Medicare for several years, you may remember hearing a lot about the Part D coverage gap, commonly called the donut hole.
That terminology still causes confusion.
The traditional coverage gap phase was eliminated beginning in 2025 as part of the Part D benefit redesign.
So if you’re reading older Medicare articles that spend a lot of time explaining how to get through the donut hole, make sure you’re looking at current Medicare information.
Part D has changed significantly.
Prior Authorization, Step Therapy and Quantity Limits: Three Rules You Should Know
Finding your prescription on a plan’s formulary is important.
But it isn’t always the end of the story.
A Part D plan may place certain coverage requirements on a medication.
Three terms you may encounter are prior authorization, step therapy and quantity limits.
Prior Authorization
Prior authorization means the plan may require your prescriber to provide additional information or obtain approval before the plan will cover a particular medication under its rules.
Step Therapy
Step therapy may require you to try another covered medication first before the plan covers a different drug.
There can be exceptions depending on the circumstances.
Quantity Limits
A quantity limit restricts how much of a medication the plan will cover during a particular period.
These rules are another reason two plans that both list your prescription as covered may not necessarily work the same way for you.
From My Office
This is where I encourage people to look beyond:
“Yes, my drug is covered.”
The next question should be:
“Are there any restrictions attached to it?”
If you take an important medication regularly, knowing about prior authorization, step therapy or quantity limits before enrolling can prevent an unpleasant surprise later.
What Is the Medicare Prescription Payment Plan?
Another Part D feature people should understand is the Medicare Prescription Payment Plan.
This program gives people with Medicare prescription drug coverage the option to spread their out-of-pocket prescription drug costs across monthly payments during the calendar year instead of paying the entire amount at the pharmacy when the prescription is filled.
This can be helpful for someone who has high prescription costs early in the year and would rather spread those costs out.
But there is a very important distinction.
The Medicare Prescription Payment Plan Does Not Lower Your Drug Costs
The program is a payment option, not an additional drug discount.
It changes when you pay your out-of-pocket prescription costs.
It doesn’t necessarily change how much you ultimately owe.
For example, someone who fills an expensive medication early in the year may prefer not to pay a large amount at the pharmacy all at once.
The Medicare Prescription Payment Plan may allow that person’s applicable out-of-pocket costs to be divided into payments over the remaining months of the calendar year.
Who Might Benefit From It?
The program may be particularly worth investigating if you expect to have significant out-of-pocket prescription costs early in the year.
However, whether it helps depends on your individual situation.
Someone with relatively small and predictable prescription costs may not receive the same cash-flow benefit.
Key Takeaway
Remember the difference:
The $2,100 Part D out-of-pocket cap limits applicable annual out-of-pocket spending on covered Part D drugs in 2026.
The Medicare Prescription Payment Plan provides another way to pay those out-of-pocket costs over time.
They are related to prescription spending, but they are not the same thing.
A Part D Plan Can Change From One Year to the Next
One of the biggest mistakes Medicare beneficiaries can make is assuming that because their Part D plan worked well this year, it will automatically be their best option next year.
Part D plans can change.
Depending on the plan and year, changes may involve things such as:
- Monthly premiums
- Deductibles
- Drug formularies
- Drug tiers
- Copayments or coinsurance
- Pharmacy networks
- Preferred pharmacies
- Coverage restrictions
Your own prescriptions can change too.
That is why Medicare prescription drug coverage deserves an annual review.
From My Office
I don’t believe in changing Medicare coverage simply for the sake of changing it.
If your current coverage continues to fit your needs, staying with it may make sense.
But there is a difference between choosing to stay after reviewing your coverage and simply assuming nothing changed.
Every year, compare what the plan will look like for the upcoming year against the medications you’re currently taking.
That simple review can sometimes uncover changes that would otherwise show up unexpectedly at the pharmacy.
Do You Have to Enroll in Medicare Part D?
Medicare Part D is optional, but that does not mean you should automatically ignore prescription drug coverage if you don’t currently take many medications.
One of the questions I hear is:
“Why should I pay for prescription drug coverage if I barely take any prescriptions?”
The answer involves something many people don’t learn about until it’s too late: the Medicare Part D late enrollment penalty.
You generally want to make sure you have either Medicare drug coverage or other prescription drug coverage that Medicare considers creditable.
The Medicare Part D Late Enrollment Penalty
You may owe a Part D late enrollment penalty if, after your Initial Enrollment Period is over, you go 63 days or more in a row without Medicare drug coverage or other creditable prescription drug coverage.
The penalty is generally added to your Part D premium.
And unlike a one-time late fee, you may have to pay the penalty for as long as you have Medicare drug coverage.
How Is the Part D Late Enrollment Penalty Calculated?
Medicare calculates the penalty based on how long you went without Part D or other creditable prescription drug coverage.
The calculation generally uses 1% of the national base beneficiary premium for each full uncovered month, rounded to the nearest $0.10.
Because the national base beneficiary premium can change each year, the dollar amount of your penalty can change too.
That is why delaying Part D without understanding the rules can become an expensive mistake.
From My Office
If someone tells me:
“I don’t take any medications, so I don’t need Part D,”
my next question is:
“Do you have other creditable prescription drug coverage?”
Those are two very different situations.
Not needing prescriptions today doesn’t necessarily protect you from a future Part D late enrollment penalty.
What Is Creditable Prescription Drug Coverage?
Creditable prescription drug coverage is coverage that is expected to pay, on average, at least as much as Medicare’s standard prescription drug coverage.
Examples may include certain:
- Employer or union prescription coverage
- Retiree coverage
- Federal employee coverage
- TRICARE coverage
- VA prescription drug coverage
However, don’t assume coverage is creditable simply because it includes prescription benefits.
Your plan or benefits administrator should tell you whether the prescription coverage is considered creditable for Medicare Part D purposes.
Keep Your Creditable Coverage Notice
If you receive a notice stating that your prescription coverage is creditable, keep it with your important Medicare documents.
You may need to show proof of that coverage later.
Aja’s Medicare Tip
If you’re approaching Medicare eligibility and plan to keep employer, union or retiree coverage, don’t ask only:
“Do I have prescription coverage?”
Ask:
“Is my prescription drug coverage creditable for Medicare Part D?”
That one word—creditable—can make a very important difference.
How to Compare Medicare Part D Plans the Right Way
Now we get to the question that matters most:
How should you actually choose a Part D plan?
I recommend starting with your prescriptions—not the insurance company and not the monthly premium.
Step 1: Make a Complete Medication List
For every prescription, write down:
- Exact medication name
- Dosage
- Quantity
- How often you take it
Be specific.
Different strengths and quantities can produce different costs.
Step 2: Check Each Plan’s Formulary
Make sure your medications are covered.
Then go one step further.
Look at the tier assigned to each drug and whether there are restrictions such as prior authorization, step therapy or quantity limits.
Step 3: Check Your Pharmacy
Find out whether your preferred pharmacy participates in the plan’s network and whether it is considered a preferred pharmacy.
Then compare the estimated costs at other convenient pharmacies.
You may be surprised by the difference.
Step 4: Look Beyond the Monthly Premium
Consider:
- Monthly premium
- Deductible
- Copayments
- Coinsurance
- Medication tiers
- Pharmacy pricing
- Coverage restrictions
- Estimated annual drug costs
This gives you a much more meaningful comparison.
Step 5: Consider What Could Change
No one can predict every medication they may need in the future.
But you can choose based on the best information you have today and review your coverage annually.
That’s much better than choosing based on an advertisement or premium alone.
The Part D Comparison Checklist I Use With Clients
Before choosing prescription drug coverage, I would want answers to these questions:
- Are all of your current prescriptions covered?
- What tier is each medication on?
- What will you pay for each prescription?
- Does the plan have a deductible?
- Which medications does the deductible apply to?
- Are there prior authorization, step therapy or quantity-limit requirements?
- Is your pharmacy in the network?
- Is your pharmacy preferred?
- Would another convenient pharmacy lower your costs?
- What is your estimated total annual cost, not just your monthly premium?
If you can answer those questions, you’re doing a much more meaningful Part D comparison.
Common Medicare Part D Mistakes to Avoid
Understanding what not to do can be just as important as understanding how Part D works.
Mistake #1: Choosing the Lowest Monthly Premium
A lower premium doesn’t automatically mean lower total prescription costs.
Mistake #2: Checking Whether a Drug Is Covered but Ignoring Its Tier
Coverage is only part of the equation.
Tier placement can affect what you pay.
Mistake #3: Ignoring the Pharmacy Network
Your pharmacy can influence your prescription costs.
Mistake #4: Assuming You Don’t Need Part D Because You Take No Medications
If you don’t have other creditable prescription drug coverage, delaying enrollment could potentially result in a future late enrollment penalty.
Mistake #5: Assuming Your Current Plan Will Stay the Same
Plans and formularies can change from year to year.
Review your coverage annually.
Mistake #6: Choosing a Plan Based on Someone Else’s Prescriptions
Your spouse, neighbor or friend may love a particular drug plan.
That doesn’t mean it’s the right plan for you.
Their medications may be completely different from yours.
Mistake #7: Forgetting About Coverage Restrictions
Prior authorization, step therapy and quantity limits can matter just as much as seeing your medication listed on the formulary.
Frequently Asked Questions About Medicare Part D
Does Medicare Part D Cover Every Prescription Drug?
No.
Each Part D plan has a formulary, or list of covered medications. Medicare establishes requirements for the types of drugs plans must cover, but formularies and coverage rules can differ among plans.
That’s why you should check your individual prescriptions before enrolling.
What Is the Medicare Part D Out-of-Pocket Cap for 2026?
For 2026, the annual out-of-pocket cap for covered Part D drugs is $2,100.
After you reach the applicable threshold, you generally pay $0 out of pocket for covered Part D drugs for the remainder of the calendar year.
What Is the Maximum Part D Deductible in 2026?
The maximum Part D deductible for 2026 is $615.
Individual plans may charge a lower deductible, and some may have no deductible.
Does the $2,100 Cap Include My Part D Premium?
No.
Your monthly Part D plan premium does not count toward the $2,100 out-of-pocket threshold.
The cap relates to applicable out-of-pocket spending for covered Part D drugs.
Can I Get Part D With Original Medicare?
Yes.
If you have Original Medicare, you can generally enroll in a stand-alone Medicare prescription drug plan.
If you also have Medigap, remember that Medigap policies sold today generally don’t include outpatient prescription drug coverage, so you may need a separate Part D plan.
Do Medicare Advantage Plans Include Part D?
Many Medicare Advantage plans include prescription drug coverage.
These are often referred to as Medicare Advantage Prescription Drug plans, or MA-PDs.
However, not every Medicare Advantage plan works the same way, so always check the plan’s drug coverage.
Can I Change My Part D Plan?
Yes, during applicable Medicare enrollment periods.
For example, Medicare Open Enrollment runs from October 15 through December 7 each year, with changes generally taking effect January 1.
Certain circumstances may also qualify you for a Special Enrollment Period.
Can My Part D Formulary Change During the Year?
There are circumstances in which a plan’s formulary can change.
Medicare has rules governing these changes and how plans notify affected members. Depending on the situation, you may have rights or options if a change affects a medication you’re taking.
Always pay attention to notices from your plan.
Is the Medicare Prescription Payment Plan a Discount Program?
No.
The Medicare Prescription Payment Plan can help spread eligible out-of-pocket prescription costs into monthly payments over the calendar year.
It changes when you pay, not necessarily how much you pay.
What Happens If I Wait to Enroll in Part D?
If you go 63 consecutive days or more after your Initial Enrollment Period without Medicare drug coverage or other creditable prescription drug coverage, you may owe a Part D late enrollment penalty if you enroll later.
That’s why it’s important to understand whether other prescription coverage you have is creditable.
Questions to Ask Before You Choose a Part D Plan
Before enrolling, ask yourself:
- What prescriptions do I currently take?
- Are all of them on the plan’s formulary?
- What tiers are they on?
- Are there coverage restrictions?
- What is the plan’s deductible?
- What will I pay at my preferred pharmacy?
- Is another convenient pharmacy less expensive?
- What is my estimated annual prescription cost?
- Am I choosing this plan because it fits my medications—or simply because the premium looks attractive?
- Do I understand how my coverage could change next year?
The goal isn’t simply to find a Part D plan.
The goal is to choose prescription drug coverage that makes sense for you.
Final Thoughts: Medicare Part D Really Isn’t One-Size-Fits-All
Medicare Part D can seem complicated because there are premiums, deductibles, formularies, tiers, pharmacies, copayments, coinsurance and coverage rules to consider.
But the decision becomes much easier when you know what to focus on.
Start with your medications.
Then look at the formulary.
Check the tiers and restrictions.
Compare pharmacies.
Review the deductible and cost-sharing.
And finally, look at the estimated total cost—not simply the monthly premium.
A plan that works beautifully for one person may be a poor fit for someone taking completely different prescriptions.
That’s why Medicare Part D really isn’t one-size-fits-all.
About the Author
Aja Link is a licensed Medicare insurance agent serving Medicare beneficiaries in New York and New Jersey.
Aja focuses on helping people understand Medicare in plain English so they can make informed decisions about their coverage.
Her approach starts with the individual—not an insurance company or a particular plan. When helping someone evaluate prescription drug coverage, she considers their medications, dosages, preferred pharmacies, budget and overall Medicare needs.
She believes Medicare guidance should be educational, personal and pressure-free.
Whether someone is approaching 65, reviewing Medicare prescription drug coverage or trying to understand how their existing Medicare coverage works, Aja’s goal is to make Medicare easier to understand and help each person evaluate the options available for their individual situation.
Need help understanding your Medicare prescription drug coverage?
Aja Link
Licensed Medicare Insurance Agent
New York & New Jersey
Phone: 516-313-8918
Email: ajaglink@gmail.com
There is no obligation to enroll when requesting information.
References
Medicare.gov — Medicare Prescription Drug Coverage (Part D)
Medicare.gov — Drug Formularies and Coverage Rules
Medicare.gov — Part D Late Enrollment Penalty
Medicare.gov — Creditable Prescription Drug Coverage
Medicare.gov — Medicare Prescription Payment Plan
Centers for Medicare & Medicaid Services — 2026 Medicare Part D Benefit Information
Medicare Disclaimer
This article is for educational purposes only and is not intended to provide legal, medical or tax advice.
Medicare Part D plan availability, premiums, deductibles, formularies, pharmacy networks, drug tiers, copayments, coinsurance and coverage requirements vary by plan and may change from year to year.
The costs and Medicare rules discussed in this article are based on 2026 Medicare information and may change in future years.
Always review current Medicare information and official plan documents before enrolling in or changing Medicare prescription drug coverage.
Not connected with or endorsed by the U.S. government or the federal Medicare program.