The best Part D plan for you depends on which drugs you take, which pharmacies are near you, and how much you are willing to spend out of pocket

There is no single "best" Part D plan because the right choice is different for every person. A plan that costs almost nothing for someone taking blood pressure medication might cost hundreds of dollars a month for someone on a cancer drug. The same plan might have your preferred pharmacy in-network at one location and out-of-network at another. Your job is to find the plan that costs you the least for your specific situation — and that plan may change every year.

The fastest way to do this is to use the Medicare Plan Finder tool on Medicare.gov. You enter the drugs you take (or will take), your preferred pharmacies, and your zip code. The tool shows you every Part D plan available in your area, ranked by your estimated out-of-pocket cost for the year. You can compare plans side by side, see which pharmacies are in-network, and check the formulary — the list of drugs each plan covers — before you choose.

Key Takeaways

  • Use the Medicare Plan Finder on Medicare.gov to compare plans based on your actual drugs and pharmacies, not on plan names or star ratings alone.
  • Part D plans vary widely in monthly premium, deductible, and copay amounts, so the cheapest premium is not always the cheapest plan overall.
  • Your drugs must be on a plan's formulary to be covered, and formularies change every year, so you need to check each January.
  • Mail-order pharmacies and 90-day supplies often cost less per dose than 30-day fills at retail pharmacies, even if the upfront cost looks higher.
  • You can switch Part D plans once a year during the annual enrollment period (October 15 to December 7), and you should compare plans every year because costs and coverage change.

How Part D plans charge you: premiums, deductibles, and copays

Every Part D plan has three costs you need to understand. The monthly premium is what you pay to the insurance company whether you fill a prescription or not. The deductible is the amount you pay out of pocket before the plan starts to help pay for drugs — some plans have no deductible. The copay (or coinsurance) is what you pay at the pharmacy each time you fill a prescription.

A plan with a low premium might have a high deductible and high copays. A plan with no deductible might have a higher premium. The Plan Finder tool adds these up for you based on your drugs, so you can see the total cost, not just the premium. This matters because a plan that costs $15 a month might end up costing you $300 more per year than a plan that costs $35 a month, depending on what you take.

Copays also depend on the drug's tier. Tier 1 drugs (usually generics) have the lowest copay. Tier 2 drugs (brand-name with a generic available) cost more. Tier 3 and Tier 4 drugs (brand-name with no generic, or specialty drugs) have the highest copays. If you take a Tier 4 drug, the copay can be $100 or more per fill. Check the formulary to see which tier your drugs are on before you choose a plan.

Using the Medicare Plan Finder to compare your options

Go to Medicare.gov and select "Find care providers and suppliers" or search for "Medicare Plan Finder." You will see a box that says "Find health and drug plans." Click on it. You will need your zip code and the names and doses of every drug you take (or expect to take in the next year). If you do not know the dose, check your prescription bottle or call your pharmacy.

Enter your drugs one at a time. The tool will show you a list of Part D plans ranked by your estimated yearly out-of-pocket cost. The top of the list is usually the cheapest option for your specific drugs. Scroll down to see other plans. Click on any plan name to see the full details: the monthly premium, deductible, copay for each drug, and which pharmacies are in-network.

Check the pharmacy section carefully. Some plans have your local pharmacy in-network but charge a higher copay there than at a mail-order pharmacy. Some plans do not include your preferred pharmacy at all. If a plan does not show your pharmacy, call the plan's customer service number (on the plan details page) and ask whether your pharmacy is in-network. In-network pharmacies cost less; out-of-network pharmacies cost significantly more.

Why formularies change and why you must check every year

A formulary is the official list of drugs a plan covers. It changes every January 1. A drug that was on your plan's formulary last year might not be this year. A drug might move to a higher tier, which means a higher copay. A drug might be removed entirely, which means you would have to switch to a different drug or switch to a different plan.

This is why you cannot assume your current plan will work next year. Every October, during the annual enrollment period, you should run the Plan Finder again with your current drugs. If your plan is still the cheapest option, you can stay. If a different plan is now cheaper, or if your drugs are no longer covered the same way, you can switch. You have until December 7 to make the change, and it takes effect January 1.

If a drug is removed from your plan's formulary mid-year and you have no other option, you can request an exception. Call your plan and ask for a formulary exception or prior authorization. The plan may cover the drug anyway, or it may require you to try a different drug first. This process takes time, so do not wait until you run out of medication to ask.

Mail-order and 90-day supplies often cost less than retail

Many Part D plans offer a lower copay if you use mail-order pharmacy or fill a 90-day supply instead of a 30-day supply. For example, a plan might charge $10 for a 30-day fill at a retail pharmacy but only $20 for a 90-day fill by mail. That is $20 for three months instead of $30, which saves you money over the year.

Mail-order pharmacies take longer — usually 7 to 14 days — so plan ahead and do not wait until you are out of medication. Some people use mail-order for maintenance drugs (blood pressure, cholesterol, diabetes) that they take every day and do not need to change, and use retail pharmacy for short-term drugs (antibiotics, pain medication) that they might need quickly.

Check the Plan Finder to see which copay applies to mail-order and which to retail for each of your drugs. Some plans charge the same copay either way. Some plans do not offer mail-order at all. If mail-order saves you money and you are willing to wait, it is worth using.

Star ratings and customer service: what they tell you

Medicare publishes star ratings for every Part D plan based on customer satisfaction, drug pricing, and service quality. Plans are rated from 1 to 5 stars. A 5-star plan is considered excellent; a 1-star plan has more complaints. However, a 5-star plan might not be the cheapest for your drugs, and a 3-star plan might be.

Star ratings are useful as a tie-breaker. If two plans cost you about the same amount, choose the one with higher stars. But do not choose a more expensive plan just because it has more stars. Your out-of-pocket cost matters more than the rating.

Customer service quality also matters if you have questions about coverage or need to request an exception. Look at the plan's customer service phone number and hours on the plan details page. Some plans have 24-hour phone support; others have limited hours. If you think you will need help, a plan with longer hours might be worth a slightly higher cost.

What to do if your drug is not covered or costs too much

If a drug you need is not on any plan's formulary, or if every plan charges a copay you cannot afford, you have options. First, ask your doctor whether a generic or lower-tier drug would work instead. Many brand-name drugs have generic versions that cost much less. Your doctor might be willing to switch you if the generic is medically equivalent.

Second, ask your plan for a formulary exception. Call the plan's customer service number and explain that the drug is medically necessary and that you cannot afford the copay or that the plan does not cover it. The plan may approve an exception, especially if you have tried other drugs and they did not work. This process can take a few days to a few weeks.

Third, look into patient information programs run by drug manufacturers. Many pharmaceutical companies offer free or low-cost drugs to people who cannot afford them. You can search for programs on the manufacturer's website or call the drug's customer service line. You will usually need to provide proof of income.

Frequently Asked Questions

Can I switch Part D plans in the middle of the year?

No, except in rare cases. You can switch during the annual enrollment period (October 15 to December 7) and the change takes effect January 1. If you have a life event like losing employer coverage or moving to a new state, you may be able to switch outside this window. Call Medicare at 1-800-MEDICARE to ask.

What happens if I do not choose a Part D plan?

If you are on Original Medicare and do not choose a Part D plan when you first become may be able to access, you may pay a late enrollment penalty for as long as you have Part D coverage. The penalty is about 1% of the national average Part D premium per month of delay. If you already have drug coverage through an employer or union, you may not have to pay the penalty.

Do I have to use the Plan Finder, or can I call a plan directly?

You can do either. The Plan Finder is faster and shows you all plans at once, ranked by cost. If you prefer to talk to someone, call Medicare at 1-800-MEDICARE and a counselor can help you compare plans over the phone. Some local Area Agencies on Aging also offer free one-on-one help with plan selection.

What if my preferred pharmacy is out-of-network?

You can still use it, but you will pay more — usually the full price of the drug, or a much higher copay. Some plans allow you to request an exception to add your pharmacy to the network, though this is not may provide. Call the plan and ask. If the plan will not add your pharmacy, you may need to switch plans or switch to a pharmacy that is in-network.

How do I know if a generic drug is the same as the brand-name drug?

The FDA requires generic drugs to have the same active ingredient, strength, and form as the brand-name drug. They work the same way in your body. The difference is usually the inactive ingredients (fillers, dyes) and the appearance. If a generic does not work for you, ask your doctor to request a brand-name exception from your Part D plan.