Medicare covers prescription drugs through Part D, but the specific medications covered depend on which plan you choose

Medicare Part D is the prescription drug coverage piece of Medicare. Every Part D plan has a formulary — a list of medications the plan covers — and that list differs from plan to plan. Your plan might cover a drug that another plan does not, or it might cover the same drug but require you to pay more for it. This means you need to check your own plan's formulary, not a general list, to know what you will pay.

Part D covers most prescription drugs, including brand-name and generic medications. It does not cover over-the-counter drugs, vitamins, or drugs used for cosmetic purposes. Some drugs require your doctor to get prior approval from your plan before you fill the prescription, and some drugs have quantity limits — meaning the plan will only cover a certain amount per month or per year.

Key Takeaways

  • Every Part D plan publishes its own formulary online, and you can search it by drug name to see if your medication is covered and what tier (price level) it sits on.
  • If your plan does not cover a drug your doctor prescribed, you can ask your doctor to request a coverage exception, which the plan must review within 72 hours.
  • Some drugs require prior authorization — your doctor must get approval from the plan before the pharmacy will fill the prescription.
  • Your out-of-pocket costs for the same drug vary widely between plans, so comparing formularies during the annual enrollment period can save you hundreds of dollars per year.

How to find your plan's formulary and check coverage

The fastest way is to go to Medicare.gov and use the Plan Finder tool. You enter your medications, and the tool shows you which plans cover each one and what you will pay. You can also visit your plan's website directly — every Part D plan publishes its formulary as a searchable PDF or database. Search by the drug name (brand name or generic), and the formulary will tell you the tier and any restrictions.

If you are already enrolled in a plan, you can call the customer service number on your insurance card. A representative can tell you whether a specific drug is covered, what your copay or coinsurance will be, and whether your doctor needs to request prior authorization. Keep the drug name, strength, and quantity handy when you call — for example, "metformin 500 mg, 90 tablets per month."

Understanding drug tiers and what you pay

Part D plans organize drugs into tiers, usually four or five levels. Tier 1 drugs (often generic) have the lowest copay. Tier 2 and 3 drugs (preferred brand-name and non-preferred brand-name) cost more. Tier 4 and 5 drugs (specialty drugs) have the highest copays, sometimes $100 or more per prescription. Your plan's formulary lists which tier each drug is on.

Your actual out-of-pocket cost also depends on where you are in the coverage year. Early in the year, you pay your copay or coinsurance. Once your total drug costs reach a certain amount (called the initial coverage limit), you enter the coverage gap, where you pay a higher percentage of the drug cost. Once your out-of-pocket spending reaches the catastrophic threshold, Medicare covers most of the cost for the rest of the year.

What happens if your medication is not covered

If your plan's formulary does not include your drug, you have options. First, ask your doctor whether a covered alternative medication in the same drug class might work for you. Many plans cover multiple drugs for the same condition — for example, several blood pressure medications — so switching to a covered one may be possible.

If you and your doctor believe the covered alternatives will not work, you can request a coverage exception. Your doctor submits a written request to your plan explaining the medical reason why you need that specific drug. The plan must respond within 72 hours (or 24 hours if it is urgent). If the plan denies the exception, you can appeal the decision. During the appeal, your pharmacy can usually fill the prescription while the plan reviews it, so you do not run out of medication.

Prior authorization and quantity limits

Some drugs require prior authorization, meaning your doctor must contact the plan and get approval before the pharmacy will fill the prescription. This is not a denial — it is a safety check. Your doctor's office usually handles this, but it can add a few days to getting your prescription filled. Ask your doctor's office to submit the request as soon as possible if you are running low on medication.

Quantity limits mean the plan will only cover a certain amount of a drug per month or per year. For example, a plan might cover only 30 tablets of a pain medication per month. If your doctor prescribes 60 tablets, you will have to pay out of pocket for the extra 30, or your doctor can request an exception. Again, your doctor's office can handle this request.

Changing your plan if your drugs are not covered well

If your current plan does not cover your medications well or your copays are too high, you can switch plans during the annual enrollment period, which runs from October 15 to December 7 each year. Use Medicare.gov's Plan Finder again, enter your medications, and compare what each plan will charge you. Sometimes switching saves hundreds of dollars per year, even though you pay a monthly premium for the new plan.

If you have a life-changing event — such as a new diagnosis, a move to a different state, or loss of other insurance — you may be able to change plans outside the annual enrollment period. Call Medicare at 1-800-MEDICARE to ask whether you may have access to for a special enrollment period.

Brand-name drugs and generic alternatives

Most Part D plans charge less for generic drugs than for brand-name drugs. A generic drug has the same active ingredient, strength, and form as the brand-name version but costs less because the manufacturer did not have to develop and test it. If your plan covers both a generic and a brand-name version of the same drug, the generic will usually be on a lower tier.

If your doctor prescribes a brand-name drug and a generic is available, ask your pharmacist what the copay difference is. Sometimes the difference is small enough that the brand-name makes sense to you. Other times, the generic saves you significant money. Your pharmacist can also tell you whether the generic is chemically identical or whether there are any known differences in how people respond to it.

Frequently Asked Questions

Can I get my prescription filled while my doctor requests a coverage exception?

Many plans allow the pharmacy to fill the prescription while the exception is being reviewed, especially if it is urgent. Ask your pharmacist whether they can do this. If not, your doctor's office should submit the exception request right away — the plan has 72 hours to respond.

What if I move to a different state during the year?

You can change to a Part D plan available in your new state. Contact Medicare at 1-800-MEDICARE or visit Medicare.gov to see which plans serve your new address. You may be able to switch outside the annual enrollment period because of your move.

Do all Part D plans cover the same drugs?

No. Each plan creates its own formulary, so coverage varies. Two plans from the same insurance company may have different formularies. Always check your specific plan's formulary, not a general list.

What if my copay is so high I cannot afford my medication?

Talk to your doctor and pharmacist about lower-cost alternatives. You can also ask your plan about patient information programs or manufacturer discounts. Some drug makers offer free or reduced-cost medications to people who meet income requirements.

How often can I check my plan's formulary?

You can check it anytime. Plans update their formularies annually, and the new formulary takes effect January 1. If a drug you take is removed from the formulary, your plan must notify you before the change happens, and you can request a coverage exception or switch plans.