Tirzepatide (Mounjaro, Zepbound)

How Medicare covers it

Part D (once-weekly self-injection pens used at home). Part A during a covered inpatient stay. No Part B clinician-administered form in the CMS Part B spending file.

What it treats

As Mounjaro, tirzepatide is used along with diet and exercise to improve blood sugar control in adults and children 10 years and older with type 2 diabetes. In adults with type 2 diabetes who are at high risk, it is also used to lower the risk of major cardiovascular events — cardiovascular death, non-fatal heart attack, and non-fatal stroke. It is a once-weekly injection under the skin. This package also lists the same drug as Zepbound, the form used for weight management and obstructive sleep apnea.

What it is for, in depth

Mounjaro (tirzepatide) is a once-weekly dual GIP/GLP-1 injection for type 2 diabetes. The Mounjaro label covers two uses: as an add-on (adjunct) to diet and exercise to improve blood sugar control in adults and pediatric patients 10 years and older with type 2 diabetes, and to reduce the risk of major adverse cardiovascular events (cardiovascular death, non-fatal heart attack, or non-fatal stroke) in adults with type 2 diabetes who are at high risk for these events. It fits in the treatment path as a weekly injectable used alongside diet and exercise, on its own or with other diabetes medicines as the prescriber directs; dosing starts low at 2.5 mg and steps up every 4 weeks or more as needed and tolerated. The forms in this package are 0.5 mL single-dose auto-injectors for both brands — Mounjaro and Zepbound — at 5, 10, 15, 20, 25, and 30 mg/mL, which deliver the 2.5 mg, 5 mg, 7.5 mg, 10 mg, 12.5 mg, and 15 mg weekly doses, plus Zepbound 2.4 mL pen injectors at 4.17, 8.33, 12.5, 16.7, 20.8, and 25 mg/mL. The Zepbound forms in the package are the same drug sold for weight management and obstructive sleep apnea under a separate label.

How it works

Tirzepatide is a dual GIP and GLP-1 receptor agonist — it activates the receptors for two natural gut hormones, GIP and GLP-1. It increases insulin release from the pancreas in a glucose-dependent way (both the first and second phases) and lowers glucagon levels, which lowers blood sugar. A fatty-acid part of the molecule binds to albumin in the blood and prolongs its half-life, which is why it can be given once a week. It also delays gastric emptying (slows how fast the stomach empties).

How it is taken

Injected under the skin (subcutaneously) once a week, at any time of day, with or without meals, in the abdomen, thigh, or the back of the upper arm (by another person), rotating sites with each dose. The starting dose is 2.5 mg once weekly; if more blood sugar control is needed, the dose is raised in 2.5 mg steps, waiting at least 4 weeks on each dose. The maximum is 15 mg once weekly in adults and 10 mg once weekly in children. If a dose is missed, take it within 4 days (96 hours); if more than 4 days have passed, skip it and take the next dose on the regular day.

Common side effects

The most common side effects in trials (5% or more of adults) were stomach-related: nausea (12% to 18% across the 5 mg, 10 mg, and 15 mg doses), diarrhea (12% to 17%), decreased appetite (5% to 11%), vomiting (5% to 9%), constipation (6% to 7%), indigestion (dyspepsia, 5% to 8%), and abdominal pain (5% to 6%). These effects are most likely when treatment starts and when the dose is raised, which is why the dose goes up slowly.

Serious warnings

Mounjaro can cause acute pancreatitis (inflammation of the pancreas), which has sometimes been fatal — stop it and get care for persistent or severe abdominal pain. Severe stomach and bowel reactions occur, and it is not recommended in severe gastroparesis (stomach paralysis). Vomiting and diarrhea can cause dehydration and acute kidney injury. Gallbladder disease (gallstones, gallbladder inflammation), temporary worsening of diabetic retinopathy, and serious allergic reactions (anaphylaxis, angioedema) have been reported. Because it delays stomach emptying, it has been linked rarely to pulmonary aspiration during general anesthesia or deep sedation — tell the surgical team you take it. Never share a Mounjaro KwikPen between patients.

Boxed warning

BOXED WARNING — RISK OF THYROID C-CELL TUMORS: In rats, tirzepatide causes dose-dependent and treatment-duration-dependent thyroid C-cell tumors at clinically relevant exposures. It is unknown whether Mounjaro causes thyroid C-cell tumors, including medullary thyroid carcinoma (MTC), in humans. Mounjaro must not be used by patients with a personal or family history of MTC or with Multiple Endocrine Neoplasia syndrome type 2 (MEN 2). Patients should be told about the possible risk and about symptoms of thyroid tumors — a mass in the neck, trouble swallowing, shortness of breath, or persistent hoarseness.

Who should be careful

Do not use Mounjaro if you have a personal or family history of medullary thyroid carcinoma or MEN 2, or a known serious allergy to tirzepatide or its ingredients. It is not recommended if you have severe gastroparesis. People with a history of diabetic retinopathy should be monitored for worsening. In pregnancy, animal studies showed harm to the fetus (growth reductions and abnormalities), and the label says it should be used only if the potential benefit justifies the potential risk to the fetus. Tell your prescriber about any planned surgery or procedure requiring anesthesia or deep sedation.

Major interactions

Using Mounjaro with insulin or an insulin secretagogue (such as a sulfonylurea) raises the risk of low blood sugar (hypoglycemia), including severe hypoglycemia; the prescriber may lower the dose of the insulin or secretagogue when Mounjaro is started. Because Mounjaro delays gastric emptying, it can change how oral medicines are absorbed — extra care is needed with oral medicines that need a certain blood level to work or have a narrow therapeutic index (for example, warfarin). Oral birth control pills may not work as well: patients are advised to switch to a non-oral method or add a barrier method for 4 weeks after starting Mounjaro and for 4 weeks after each dose increase.

Why it is in its tier

Tirzepatide is most often placed on Tier 3 in 2027 Medicare Part D formularies — the modal tier, used by 91.62% of listing plans — and it is listed by 97.12% of plans (5,337 of 5,495). Tier 3 is the preferred brand tier, with mid-level copays or coinsurance. That fits tirzepatide's status as a brand-only drug (Mounjaro and Zepbound) with no generic version. The CMS Part D dashboard put average program spending for Mounjaro at $7,083.70 per beneficiary for 2024, a high cost level. That dashboard figure is a program average, not your copay. The tier shown is the most common one; individual plans vary, so check your own plan's formulary.

Sources

• MOUNJARO (TIRZEPATIDE) INJECTION, SOLUTION MOUNJARO KWIKPEN (TIRZEPATIDE) INJECTION, SOLUTION [ELI LILLY AND COMPANY] — DailyMed
• MedlinePlus — National Library of Medicine
• MedlinePlus — Tirzepatide

What official patient guides say

Tirzepatide comes as a liquid in a vial or in a pre-filled single-use pen or single-patient-use Kwikpen, and it is injected under the skin once a week, with or without meals, at any time of day. It can be injected in the abdomen, thigh, or upper arm, and you should rotate the injection site with each dose. If you miss a dose, inject it as soon as you remember within 4 days, but if more than 4 days have passed, skip the missed dose and continue your regular schedule, and do not inject two doses within 3 days of each other. Store tirzepatide in the refrigerator between 36 and 46 degrees Fahrenheit in its original carton to protect it from light, though single-dose pens or vials can be stored at room temperature for 21 days if needed.

Source: MedlinePlus — Tirzepatide

Part D formulary coverage

Source: CMS Prescription Drug Plan Formulary, Pharmacy Network, and Pricing Information Files — Monthly file 2026-10-15 (plan year 2027), file 2027_20261008.zip (data.cms.gov dataset ed1496ea-23e7-41f1-9292-172fa842ccfb): basic drugs formulary file + plan information file, both dated 20261031 inside the zip; downloaded and aggregated 2026-10-30. Medication RxCUI sets resolved through the NLM RxNav (RxNorm) API.

What you pay

Without insurance, the cash benchmark is $538.7578 per unit (MOUNJARO 10 MG/0.5 ML PEN) — about $16162.73 for 30 units. NADAC benchmark — the average price pharmacies pay (CMS, as of 2026-11-04). Pharmacy shelf prices vary.

A tier is not a price; what you pay depends on your plan, pharmacy, and benefit stage; Extra Help or Medicaid can lower it further.

Sources: CMS Plan Benefit Package + formulary data; CMS NADAC · Checked 2026-11-08

Coverage by plan and tier

Of the 5,495 Medicare drug plans we track for 2027, 5,337 list Tirzepatide (Mounjaro, Zepbound) — 97.1% of plans. Most of those plans put it on Tier 3: 4,890 plans, 91.6% of the plans that list it. Other plans place it on Tier 4 (274 plans), Tier 1 (122 plans) or Tier 2 (45 plans). For example: Aetna Medicare Dual Extra (HMO D-SNP) puts it on Tier 3; Aetna Medicare Dual Extra Care (PPO D-SNP) puts it on Tier 3; Aetna Medicare Value Plus (PPO) puts it on Tier 3. You can compare these plans side by side on our Medicare Advantage hub. A tier is not a price. What you pay also depends on whether you have met your plan's deductible, whether the drug costs a flat copay or a share of the price, and whether you get Extra Help or Medicaid.

Read next

• Part D in 2027: The $700 Deductible, the $2,400 Cap, and the $35 Insulin Rule
• Extra Help in 2027: Lower Drug Copays and Who Qualifies
• Checking Medicare Savings Programs and Extra Help

Part D spending averages (2024)

Source: CMS Medicare Part D Spending by Drug (Drug Spending Dashboard), release RY26 P04 V10, data through 2024 (DSD_PTD_RY26_P04_V10_DY24_BGM.csv), downloaded 2026-10-30

Companies covering this drug

Part D and Medicare Advantage plan sponsors that list this drug on a formulary, 50 at a time.