Understanding Drug Formularies: How to Check If Your Parent's Medications Are Covered

You are managing your parent's prescriptions, and the pharmacy calls to say insurance won't cover one of their medications. Or your parent switches Medicare plans during open enrollment and suddenly a drug that was covered for years is rejected. Understanding how a formulary works — and what levers you can pull when a drug is not covered — is one of the most practical skills a caregiver can develop.

A drug formulary is the list of prescription medications that a specific insurance plan will cover. For Medicare beneficiaries, this means their Part D prescription drug plan's formulary. No two Part D plans have identical formularies, which is why a medication covered under one plan may require prior authorization, a higher copay tier, or no coverage at all under a different plan.

How a Medicare Part D Formulary Is Structured

Every Medicare Part D plan divides its covered drugs into tiers. Most plans use a 4–6 tier structure. The tier a drug falls into determines what your parent pays out of pocket per prescription.

Typical tier structure:

• Tier 1 — Preferred Generics: Lowest copay, often $0–$5 per fill. The plan's cheapest option and the default choice when a generic equivalent exists.
• Tier 2 — Non-Preferred Generics: Slightly higher copay, typically $10–$15. These are generics that the plan has not negotiated preferential pricing on.
• Tier 3 — Preferred Brand Names: Mid-range copay, often $35–$50. Brand name drugs for which the plan has negotiated pricing with the manufacturer.
• Tier 4 — Non-Preferred Brand Names: Higher copay, often $80–$100+. Brand name drugs not under a preferred contract.
• Tier 5 — Specialty Drugs: High-cost medications (biologics, cancer drugs, MS treatments) with coinsurance instead of a flat copay. The patient pays a percentage of the drug's total cost — typically 25–33%.

The most important thing to understand about tiers: the plan, not the drug manufacturer, controls tier placement. A drug that is Tier 2 on one plan may be Tier 4 on another plan from a competing insurer. This is why the specific plan your parent chooses during enrollment matters enormously when they take expensive brand name medications.

How to Look Up Whether a Drug Is Covered

Step 1: Find your parent's plan name and ID. This is on their Medicare card (for Part D it's on a separate plan card, not the red-white-and-blue Medicare card itself) or in the plan's annual Summary of Benefits.

Step 2: Go to the plan's formulary. Every Medicare Part D plan is required to publish its formulary and make it searchable. Two ways to access it:

• Medicare Plan Finder (medicare.gov/plan-compare): Enter the drugs, and the tool shows which plans cover them and at what tier. This is the most useful tool for comparison shopping during open enrollment.
• The plan's own website: Log in to your parent's plan account (or call the member services number on the card) and search the drug by name. The formulary search will show tier placement and any coverage restrictions.

Step 3: Note any restrictions. Even if a drug is on the formulary, the plan may require:

• Prior Authorization (PA): The prescribing physician must submit documentation justifying the medical necessity before the plan will approve coverage. This is common for brand name drugs, specialty medications, and drugs with covered generic alternatives.
• Step Therapy: The plan requires the patient to try and fail on a cheaper drug first before covering the requested one. Example: a plan may require a trial of generic metformin before covering a newer, more expensive diabetes drug.
• Quantity Limits: The plan will only cover a specific number of pills per month. Common for controlled substances and high-cost specialty drugs.

What to Do When a Drug Is Not on the Formulary

"Not on the formulary" is not a final answer. You have three paths.

Path 1: Request a Formulary Exception

A formulary exception asks the plan to cover a drug that is not on their formulary (or to cover a higher-tier drug at a lower tier's cost). The physician must submit a request documenting why the patient needs this specific medication and why covered alternatives are not appropriate.

The grounds for a successful formulary exception typically include:

• The patient tried the covered alternative and it caused an adverse reaction
• The patient's condition did not respond to the covered alternative
• There is a specific clinical reason the patient cannot take the formulary alternatives (contraindication, drug interaction, etc.)

Timeline: Medicare plans must respond to standard exception requests within 72 hours. If the physician marks the request as "urgent" due to the patient's health situation, the plan must respond within 24 hours.

Path 2: Step Therapy Override

If the plan requires step therapy — try Drug A before they'll cover Drug B — but your parent already tried Drug A (even years ago under a different plan), the physician can document that prior therapy. Many states have laws limiting how broadly step therapy can be applied, particularly if the patient has been stable on a medication for an extended period.

Path 3: Appeal

If a formulary exception is denied, you can appeal. The Medicare Part D appeals process has five levels:

1. Redetermination by the plan
2. Independent Review Entity (IRE) review
3. Office of Medicare Hearings and Appeals (OMHA)
4. Medicare Appeals Council
5. Federal District Court

In practice, most coverage issues are resolved at level 1 or 2. The key to a successful appeal at any level is physician documentation of medical necessity. A letter from the physician explaining why the denied drug is necessary and why alternatives are contraindicated or inadequate is the most powerful document in the appeal.

Important: Do not delay starting the process. Drugs can be expensive out-of-pocket while an appeal is pending. If your parent needs the medication now, ask whether the physician has samples, whether there is a manufacturer patient assistance program, or whether GoodRx or a similar discount program makes the out-of-pocket cost manageable while the appeal is resolved.

Formulary Changes During the Plan Year

Medicare Part D plans can change their formularies mid-year in limited circumstances — adding drugs, changing tier placement, or adding restrictions. However, plans are prohibited from removing a drug from the formulary mid-year (except in rare cases like FDA withdrawal).

If a drug's tier placement changes, which affects your parent's copay, the plan must give at least 60 days' notice. If a drug is added to a prior authorization requirement mid-year, the plan must give 60 days' notice to currently taking beneficiaries.

The annual formulary change that matters most: Every October, Medicare Part D plans publish their updated formularies for the coming year. This is the document to review before the open enrollment period (October 15 – December 7). If a drug your parent currently takes is moving to a higher tier or being dropped from the formulary, this is the trigger to compare plans and potentially switch.

Comparing Plans by Drug Costs

The most effective way to compare Medicare Part D plans for a parent on multiple medications is to enter their complete drug list into the Medicare Plan Finder tool. The tool calculates the estimated annual total cost for each drug under each available plan — including premiums, deductibles, and per-drug copays.

This exercise frequently reveals that the plan with the lowest monthly premium is not the plan with the lowest total annual cost. A $0-premium plan may place your parent's most expensive medication on Tier 5, making the total cost far higher than a plan with a $50/month premium that places the same drug on Tier 3.

The fields to compare for each plan:

• Total estimated annual cost (premiums + deductibles + drug copays for your parent's specific medications)
• Network pharmacy — Ensure your parent's preferred pharmacy is in the plan's network
• Mail-order pharmacy — Some plans offer significantly lower copays for a 90-day mail-order supply vs. a 30-day retail fill

Medicare Drug Costs After the 2025 Reforms

The Inflation Reduction Act significantly changed Medicare Part D costs starting in 2025:

The $2,000 out-of-pocket cap means that once your parent pays $2,000 in covered drug costs in a calendar year, their Part D cost drops to $0 for the rest of the year. For seniors on specialty medications — biologics, cancer drugs, MS treatments — this is a substantial change that eliminates the catastrophic phase coinsurance that previously had no ceiling.

The Medicare Prescription Payment Plan (M3P) allows seniors to spread their $2,000 annual out-of-pocket obligation across monthly installments rather than paying the full amount in the first months of the year (when deductibles and initial coverage phase costs hit). This is a cash-flow tool, not a cost reduction — the total annual cost is the same, but it is spread evenly.

Extra Help (Low Income Subsidy): For seniors with income below 150% of the Federal Poverty Level (approximately $22,590 for an individual in 2025), Extra Help provides near-zero drug costs — $0 deductible and generic copays of around $4.50. If your parent qualifies, apply through the Social Security Administration. Many eligible seniors are not enrolled.

One Pharmacy for All Prescriptions

While formulary management is primarily an insurance exercise, the most operationally important step for reducing medication cost chaos is consolidating all of your parent's prescriptions to one pharmacy. A single pharmacy:

• Conducts a Drug Utilization Review on every fill, flagging interactions across all medications
• Allows for medication synchronization (all refills due on the same day each month)
• Maintains a complete prescription history that emergency physicians can request access to
• Simplifies insurance billing and reduces the likelihood of coverage errors

Formulary confusion often worsens when prescriptions are scattered across multiple pharmacies, because each fill is processed in isolation.

Navigating what your parent's medications cost, what their insurance covers, and how to appeal denied claims is part of the caregiver job that no one fully warns you about. The Medication Management Kit includes tools for tracking your parent's complete drug list, understanding coverage, and communicating effectively with physicians and pharmacists — so you have the documentation you need when insurance decisions need to be challenged.