If you have Medicare and take medications for diabetes, thyroid disease, osteoporosis, or other endocrine conditions, understanding how Part D works can save you hundreds — sometimes thousands — of dollars per year. This guide explains the 2024–2025 Part D structure and what it means specifically for the medications we prescribe.
📋 Important: Medicare Part D costs change every year. This page reflects 2025 figures. Always verify current costs with your specific plan at medicare.gov or by calling 1-800-MEDICARE.
What Is Medicare Part D?
Medicare Part D is the prescription drug benefit — either a standalone plan added to Original Medicare (Parts A & B), or built into a Medicare Advantage plan (Part C). It is run by private insurers approved by Medicare, which is why costs and formularies (the list of covered drugs) vary by plan.
The 2025 Part D Cost Structure
Part D has four phases. Understanding where you are in the cycle helps you anticipate costs:
| Phase | What It Means | 2025 Amounts |
|---|---|---|
| Deductible Phase | You pay 100% of drug costs until you meet your deductible | Up to $590/year (some plans waive this for Tier 1–2 drugs) |
| Initial Coverage Phase | You pay your plan's copay or coinsurance per drug | Varies by drug tier (see below) |
| Catastrophic Coverage | After $2,000 out-of-pocket, you pay $0 for covered drugs for the rest of the year | $2,000 OOP cap (new in 2025 — a major improvement) |
🎉 2025 Major Change: The "donut hole" (coverage gap) has been eliminated. And a new $2,000 annual out-of-pocket cap means once you spend $2,000 on covered drugs, your Part D cost is $0 for the rest of the year. This is a significant improvement for patients on expensive medications.
Drug Tiers — What You'll Pay Per Prescription
Part D plans organize drugs into tiers. Higher tiers mean higher cost-sharing:
| Tier | Drug Type | Typical Cost |
|---|---|---|
| Tier 1 | Preferred generics | $0–$5 copay |
| Tier 2 | Non-preferred generics | $5–$15 copay |
| Tier 3 | Preferred brand-name drugs | $35–$50 copay |
| Tier 4 | Non-preferred brand-name drugs | $70–$100+ copay |
| Tier 5 | Specialty drugs (highest cost) | 25–33% coinsurance — often $500–$1,000+/month before cap |
Common Endocrine Medications & What to Expect
🩸 Diabetes Medications
| Medication | Typical Tier | Notes |
|---|---|---|
| Metformin (generic) | Tier 1 | Usually very low cost — $0–$5/month |
| Glipizide, glimepiride (generic sulfonylureas) | Tier 1–2 | Low cost |
| Januvia, Janumet (sitagliptin) | Tier 3–4 | Moderate cost; generic sitagliptin now available |
| Jardiance (empagliflozin) | Tier 3–5 | Varies widely by plan; prior auth often required |
| Farxiga (dapagliflozin) | Tier 3–5 | Similar to Jardiance |
| Ozempic / Rybelsus (semaglutide for diabetes) | Tier 4–5 | Covered for Type 2 diabetes (not for weight loss alone); prior auth common |
| Mounjaro / Zepbound (tirzepatide) | Tier 4–5 | Mounjaro covered for T2D; Zepbound (weight loss) often NOT covered by Medicare |
| Insulin (vials, pens) | Special rule | Insulin is capped at $35/month per Part D — regardless of plan or tier |
| Trulicity, Victoza (older GLP-1s) | Tier 3–5 | Varies; some plans prefer these over newer agents |
💉 Insulin $35 Cap: Since 2023, Medicare Part D caps insulin copays at $35 per month per covered insulin product — regardless of which plan you have. This applies to all covered insulins at any pharmacy.
🦋 Thyroid Medications
| Medication | Typical Tier | Notes |
|---|---|---|
| Levothyroxine (generic) | Tier 1 | Usually $0–$5/month — very affordable |
| Synthroid (brand levothyroxine) | Tier 3–4 | Much higher cost than generic; most patients do well on generic |
| Methimazole (generic) | Tier 1–2 | Low cost |
| Cytomel / liothyronine (T3) | Tier 2–3 | Generic available; moderate cost |
| Tapazole (brand methimazole) | Tier 3–4 | Higher cost than generic methimazole |
🦴 Osteoporosis Medications
| Medication | Typical Tier | Notes |
|---|---|---|
| Alendronate (generic Fosamax) | Tier 1–2 | Very affordable — often $0–$10 |
| Risedronate (generic Actonel) | Tier 1–2 | Low cost |
| Prolia (denosumab) | Part B — not Part D | Given by injection in office; covered under Part B at 80% after deductible |
| Reclast (zoledronic acid IV) | Part B — not Part D | Infusion in office; covered under Part B |
| Evenity (romosozumab) | Part B — not Part D | Office injection; Part B coverage |
| Forteo / Tymlos (injectables) | Tier 5 | Very high cost without assistance; manufacturer programs may help |
| Yorvipath (palopegteriparatide) | Tier 5 specialty | New drug; prior auth required; check plan formulary |
🏥 Part B vs. Part D: Drugs given in our office (like Prolia, Reclast, Evenity, and Tepezza infusions) are usually billed under Medicare Part B — not Part D. Part B covers 80% after your deductible; your supplemental plan (Medigap) typically covers the remaining 20%.
👁️ Tepezza (Thyroid Eye Disease)
Tepezza is administered as an IV infusion in an outpatient infusion center and billed under Medicare Part B. Medicare covers it for FDA-approved thyroid eye disease. You pay 20% coinsurance after the Part B deductible ($257 in 2025) unless you have a Medigap supplement. Prior authorization is required. Our office handles the PA process.
Prior Authorization (PA) — What It Is and Why It Happens
Prior authorization means your insurance requires your doctor to submit medical documentation proving the medication is medically necessary before they'll cover it. PA is extremely common for:
- GLP-1 medications (Ozempic, Mounjaro, Trulicity) — diabetes diagnosis, A1c level, and prior medication trials are typically required
- SGLT2 inhibitors (Jardiance, Farxiga) — especially for CKD or heart failure indications
- Tepezza — TED diagnosis and clinical activity score documentation required
- Forteo, Tymlos, Yorvipath — severe osteoporosis and prior bisphosphonate trial usually required
- Kerendia — T2D + CKD documentation required
Our office initiates and manages PA requests. If a PA is denied, we can file an appeal. PA approvals typically take 3–14 business days; urgent cases can be expedited. Contact our office if you're waiting more than 2 weeks for a PA decision.
CGM Coverage Under Medicare Part B
Continuous glucose monitors (CGMs) are covered under Medicare Part B — not Part D — as durable medical equipment (DME). Key rules:
- You must be on insulin OR have hypoglycemia unawareness OR have two hypoglycemic episodes documented in the prior 6 months to qualify
- Medicare covers CGMs at 80% of the Medicare-approved amount after the Part B deductible
- Covered CGMs include: Dexcom G6, Dexcom G7, Abbott FreeStyle Libre 2 and 3
- Your endocrinologist must document medical necessity and write a CGM order
- Supplies (sensors, transmitters) are also covered under Part B DME benefit
Insulin Pumps Under Medicare Part B
Insulin pumps and related supplies are covered under Medicare Part B DME. Requirements:
- Must have Type 1 diabetes OR Type 2 diabetes requiring intensive insulin management
- Must be on multiple daily injections (MDI) before pump approval
- C-peptide level and other documentation required
- Medicare covers the pump at 80% after Part B deductible; insulin for the pump is covered under Part D at the $35/month insulin cap
Strategies to Reduce Your Costs
- Ask about generics: Generic metformin, levothyroxine, alendronate, and glipizide are pennies compared to brand names
- Use the Medicare Plan Finder: At medicare.gov, compare plans based on your specific drug list — costs vary dramatically between plans
- Extra Help (Low Income Subsidy): If your income and resources are limited, you may qualify for Extra Help — which can reduce Part D costs to nearly $0
- Manufacturer assistance: For drugs not well covered, many manufacturers offer patient assistance programs (PAPs) even for Medicare patients in specific circumstances
- Medicare Savings Programs: State programs that help pay Medicare premiums, deductibles, and copays for qualifying low-income beneficiaries
- $2,000 cap benefit: If you're on expensive specialty drugs, you'll now hit the $2,000 out-of-pocket cap and pay $0 for the rest of the year — plan large fills accordingly
Key Takeaways
- The 2025 Part D out-of-pocket cap is $2,000 — after that, your covered drugs are free for the year
- Insulin is capped at $35/month under Part D for all Medicare beneficiaries
- Drugs given in our office (Prolia, Reclast, Tepezza) are covered under Part B — not Part D
- CGMs and insulin pumps are Part B DME benefits — not Part D
- Prior authorization is required for most GLP-1s, specialty osteoporosis drugs, and Tepezza — our office handles this
- Generic endocrine drugs (metformin, levothyroxine, alendronate) are very affordable under Part D
Our Team Can Help with Your Medications
All five of our providers prescribe and manage endocrine medications. Book with any member of our team:
Book an Appointment → or call 832-968-7003