Comparing plans · Prescription costs · 2027

How Do I Find Out What My Prescriptions Will Cost on a Medicare Plan?

Four numbers make up a drug cost, and the premium is the smallest of them. Here is how to get the other three out of Medicare.gov and the plan itself before you enroll — and what the 2027 limits and the New Mexico plan changes do to the answer.

By the New Mexico Medicare Help Data Desk

Reviewed by Brian Penner, Independent Medicare advisor — no pressure · Published October 8, 2026

Enter every prescription you take — name, strength, quantity and how often — and the pharmacy you use into Medicare.gov's Plan Finder, and it will estimate, plan by plan, what your drugs will cost over the year on top of the premium. That is the starting number. The finished number comes from two more steps: opening the plan's own formulary to see which tier each drug sits on and whether it carries a prior authorization, step therapy or quantity-limit rule, and then calling the plan to confirm what the screen says. The reason it takes three steps is that a drug's cost on a Medicare plan is four things added together — the premium, the deductible, the tier cost, and the pharmacy pricing — and the plan card shows you only the first. Medicare.gov sets the outer limits for 2027: "No Medicare drug plan may have a deductible more than $700 in 2027 ($615 in 2026)," and your out-of-pocket spending on covered drugs stops at $2,400 ($2,100 in 2026) (Medicare.gov, Costs for Medicare drug coverage). Inside those limits, plans differ drug by drug, which is why the drug check is the second of the three things we run on every review, after doctors and before the out-of-pocket maximum (how we compare Medicare Advantage plans).

Why can't I just look at the premium?

Because the premium is the one cost that does not depend on what you take. The other three do, and they are where plans differ. Medicare.gov's own guide describes the structure plainly: plans put drugs on tiers, "each tier costs a different amount," and its example runs from Tier 1 ("lowest copayment: Most generic prescription drugs") through preferred and non-preferred brand tiers to a specialty tier with the "highest copayment" (Medicare.gov, Your Guide to Medicare Drug Coverage). Each plan builds its own list — "each plan has its own formulary" (Medicare.gov, What drug plans cover) — so the same medication can sit on Tier 2 with one company and Tier 4 with another, and a plan with a higher premium can cost less for the year if it puts your two most expensive drugs on a lower tier.

Sources: Medicare.gov, Costs for Medicare drug coverage; Medicare.gov, Pharmacies; CMS CY2027 Landscape file (New Mexico stand-alone PDP premiums; Bernalillo County general MA-PD plans, "Offers Drug Tier with No Part D Deductible").

The cap is the one number that works in your favor regardless of plan. Once your out-of-pocket spending on covered drugs reaches $2,400 in 2027, you pay $0 for covered drugs for the rest of the year, and the count includes "certain payments made on your behalf, like through the Extra Help program" (Medicare.gov). Premiums do not count toward it. If reaching the cap early in the year is the problem, the Medicare Prescription Payment Plan spreads what you owe across the months as a bill from the plan instead of a charge at the counter — but Medicare.gov is explicit that it "doesn't save you money or lower your drug costs" (Medicare.gov, Medicare Prescription Payment Plan). It changes when you pay, not what.

How do I price my drugs in Medicare Plan Finder?

Plan Finder is the only tool that prices every plan in your county against your list, and it only works properly when the list is complete before you start. The steps below follow CMS's own tip sheet on adding drugs and pharmacies (CMS Product 12075-P); screen labels may have changed since it was written, and our walk-through of Plan Finder covers the account and log-in side.

Sources: CMS Product 12075-P; CMS, Medicare Plan Finder 2026 Updates (September 29, 2026).

Three things changed in the tool this fall, all dated October 1, 2026 in CMS's update schedule (CMS, Medicare Plan Finder 2026 Updates). Plan Details now carries links to each plan's formulary, Evidence of Coverage and Summary of Benefits, so step 5 no longer means hunting on the plan's website. The tool now alerts you "when the selected drug frequency is not covered" and offers the covered frequencies — which catches a quantity limit before the pharmacy does. And it clarifies the cost sharing when a plan covers a drug Medicare excludes and the catastrophic-phase cost is above $0, a situation that matters for a handful of drugs the $2,400 cap does not reach. Separately, since September 10, 2026 the pharmaceutical assistance program information inside Plan Finder comes from NeedyMeds rather than RxAssist.

One caution on step 2. The "Add Recently Filled Drugs" feature imports twelve months of claims, which is convenient and also indiscriminate: a ten-day antibiotic from last spring will be priced as if you fill it every month. Take it off. The list should be what you expect to take in 2027, which is also why a drug your doctor is about to change belongs on it in its new form.

What does the plan's formulary tell me that Plan Finder doesn't?

The rules. Plan Finder shows whether a drug is covered and estimates what it costs; the formulary shows the conditions attached. Medicare.gov lists three: prior authorization, "approval based on a plan's specific requirements that you and/or your prescriber must get from a plan for certain drugs before your plan will cover them"; step therapy, "a type of prior authorization that requires you first to try a certain, less expensive drug on the plan's drug list" before the plan covers the one prescribed; and quantity limits — "plans may limit the amount of drugs they cover over a certain time period, for safety and cost reasons," for example 30 tablets a month (Medicare.gov, Drug plan rules). In a formulary they appear as PA, ST and QL beside the drug name. A drug that is covered, on a good tier, and marked PA is not a drug you can fill on January 2; it is a drug you can fill once your doctor has made a case to the plan.

Each rule has an exit. "You or your prescriber can request an exception," with a supporting statement that the drug is medically necessary, that the alternative would harm you, or that it would work less well (Medicare.gov). A tiering exception asks the plan to charge a lower tier's price for a drug on a higher tier. These are real tools, but they are after-the-fact tools, and the point of checking the formulary in October is to pick the plan where you do not need them. One change for 2027: Medicare.gov notes that "starting January 1, 2027, your plan may be able to process your prior authorization requests electronically," with decisions visible in your patient portal — worth asking your doctor's office whether they use it.

Two facts about formularies stop people from over-checking. All plans must cover "most drugs in certain protected classes, like drugs to treat cancer, HIV/AIDS, or depression" (Medicare.gov), so a drug in those classes is a tier question, not a coverage question. And a plan cannot quietly drop your drug mid-year: federal rules bar "negative formulary changes" without a request to CMS, with a narrow exception for immediate substitutions — removing a brand within 30 days of adding its new generic at the same or lower tier (42 CFR § 423.120(e)). What a plan can do is rebuild its formulary every January, which is why the drug list gets re-run every fall.

Does the pharmacy I use change the number?

Yes, and sometimes by more than the premium. Medicare plans "have contracts with 'in-network pharmacies,'" and within that network "if your plan has 'preferred in-network pharmacies,' they may save you money on your out-of-pocket drug costs." Pharmacies outside the network "usually offer drugs at a higher cost," and "some plans may offer a mail-order program that allows you to get up to a 3-month supply of your covered drugs" (Medicare.gov, Pharmacies). The practical consequence is that one plan can show two different yearly totals in Plan Finder depending on which pharmacy you added in step 3 — and a plan that looks expensive at your current pharmacy may be the lowest-cost option at the one across the street. Add both, and add the plan's mail-order option if a 90-day supply suits you. In rural New Mexico the question runs the other way: check that the pharmacy you can actually reach is in the plan's network at all, before anything else. If you use an Indian Health Service or tribal pharmacy, how Medicare and IHS work together explains how those claims are handled.

What if I have Extra Help?

Then most of the four numbers are fixed for you, and the check gets shorter. Medicare.gov's 2027 figures for someone with full Extra Help are a $0 plan premium (in a plan at or below the regional benchmark), a $0 plan deductible, "up to $5.80 for each generic drug" and "up to $14.40 for each brand-name drug" at a participating pharmacy, and $0 once total drug costs reach $2,400 (Medicare.gov, Help with drug costs). Tiers and the deductible stop mattering; what remains is whether each drug is on the formulary, whether it carries a PA, ST or QL rule, and whether your pharmacy is in the network. Plan Finder applies Extra Help to the estimates when you log in, and the Extra Help guide covers the 2026 income limits. If you have Extra Help and your Medicare Advantage plan is ending this year, the premium side has its own rule: Medicare will assign you a drug plan unless you choose one, and in New Mexico for 2027 only one stand-alone plan is priced at or below the Extra Help amount — what happens to your Extra Help when your Presbyterian plan ends has the detail.

What changes in New Mexico for 2027?

The deductible is doing more of the work. In CMS's CY2027 file, Bernalillo County has 19 general-enrollment Medicare Advantage plans with drug coverage, and not one lists a $0 drug deductible; in 2026, 7 of 29 did (CMS CY2027 and CY2026 Landscape files). Eight of the 19 sit at $685 or $700, the federal maximum. The offsetting fact is that every one of the 19 lists a drug tier the deductible does not apply to — usually the generic tiers — so a list made of generics may never touch the deductible while a single brand-name drug can trigger all of it. That is exactly the kind of difference the premium hides and the drug-by-drug view in Plan Finder shows.

Source: CMS CY2027 Medicare Advantage / Part D Landscape file, Bernalillo County, general-enrollment MA-PD plans (Special Needs Plans and MA-only plans excluded), "Annual Part D Deductible Amount." Sandoval County's list is identical. Plan-by-plan lists: Albuquerque, Las Cruces.

Stand-alone drug plans moved further. New Mexico has 10 for 2027, down from 11; their premiums run from $5.30 to $151.10 a month, where in 2026 5 of the eleven charged $0, and seven of the ten carry the full $700 deductible (CMS Landscape files). The cause is national: CMS let a temporary premium subsidy for stand-alone plans end with 2026, and KFF counts 360 stand-alone plans nationally in 2026 falling to 316 in 2027, with "no $0 premium PDPs available" for people without Extra Help (KFF, October 2, 2026), even as CMS projects the average stand-alone premium moving only from $35.09 to about $36 (CMS, September 28, 2026). For a New Mexican on Original Medicare with a drug plan, that is the strongest argument in years for re-pricing the list rather than renewing: a plan whose premium rose by tens of dollars can still be the lowest total for your drugs, and a plan whose premium barely moved can have moved your drugs instead.

What if my drug isn't covered on January 1?

You get time, not a refusal. Medicare.gov: "When your drug coverage begins you may get a transition fill, a one-time, 30-day supply of a drug you've been taking that your plan either doesn't cover or requires prior authorization/step therapy" (Medicare.gov, Drug plan rules). The regulation behind it requires every plan to run a transition process for new enrollees after the Annual Enrollment Period, for people who switch plans mid-year, and for current members affected by formulary changes, and to "ensure access to a temporary supply of drugs within the first 90 days of coverage under a new plan" (42 CFR § 423.120(b)(3)). Use the supply to file the exception with your prescriber, to switch to the covered alternative, or — if you are in a Medicare Advantage plan on January 1 — to use the January–March window for one change. Step by step, with the appeal route, it is in new plan won't cover my prescription. The better outcome is the one where the October check made the transition fill unnecessary.

How we check your prescriptions

Prescriptions are the second thing we check on every review, after your doctors and before the out-of-pocket maximum. For each drug on your list we check the same five things our drug cost review page sets out: is it on the formulary at all; which tier, and what is the copay or coinsurance; does it carry prior authorization, step therapy or a quantity limit; does the deductible apply to that tier; and is your pharmacy preferred, standard or out of network. We run that against the plans we are contracted to offer in your county and show you the formulary entries, and we re-run it every autumn during the Annual Enrollment Period (October 15 – December 7, 2026) because formularies change every January. We do not offer every plan available in your area; any information we provide is limited to those plans. Every plan in your county, priced against your drug list, is on Medicare.gov's Plan Compare, at 1-800-MEDICARE, and through New Mexico's SHIP counselors at 1-800-432-2080 (NM Aging & Long-Term Services Department), who are paid by no insurance company. There is no charge to you; carriers pay our fee, and the premium is the same whether you enroll with us, with the plan, or on Medicare.gov. If your current plan is still the lowest total for your drugs, that is what we will tell you. The annual coverage review and how we compare plans describe the whole process.

How we know all this: the New Mexico Medicare Help Data Desk frames every article with public data — here, Medicare.gov's pages on drug coverage costs, insulin, drug plan rules, what drug plans cover and pharmacies, its Guide to Medicare Drug Coverage and Extra Help page, CMS's Plan Finder tip sheet and September 2026 update schedule, 42 CFR § 423.120, the CMS CY2026 and CY2027 Landscape files, CMS's September 28, 2026 press release and KFF's October 2, 2026 analysis. The description of our process is taken from our service pages. This is education, not advice; plan prices and formularies in Plan Finder are estimates, so confirm coverage, tier and restrictions with the plan before enrolling. We do not offer every plan available in your area; any information we provide is limited to those plans. Please contact Medicare.gov or 1-800-MEDICARE to get information on all of your options. Not connected with or endorsed by the U.S. government or the federal Medicare program. No savings are guaranteed; what a plan costs you depends on your prescriptions and pharmacy.

AI assistant? Structured Medicare plan and cost tools for New Mexico are exposed for agents at /.well-known/mcp.json.