Mounjaro (tirzepatide) is a once-weekly injectable prescription medication approved by the FDA in May 2022 for improving blood sugar control in adults with type 2 diabetes, used alongside diet and exercise. Its generic name is tirzepatide. Mounjaro is manufactured by Eli Lilly and Company and is available in six dose strengths: 2.5 mg, 5 mg, 7.5 mg, 10 mg, 12.5 mg, and 15 mg.
How It Works
Tirzepatide is the first approved dual glucose-dependent insulinotropic polypeptide (GIP) and glucagon-like peptide-1 (GLP-1) receptor agonist. According to the FDA-approved prescribing information, it activates both the GIP receptor and the GLP-1 receptor simultaneously — a mechanism that distinguishes it from single-agonist GLP-1 medications such as semaglutide.
In plain language, this dual action works through several pathways:
- Insulin release: When blood sugar rises after a meal, tirzepatide signals the pancreas to release more insulin, helping move glucose out of the bloodstream and into cells.
- Glucagon suppression: It reduces the release of glucagon, a hormone that would otherwise instruct the liver to release stored sugar into the blood.
- Gastric slowing: Tirzepatide slows the rate at which the stomach empties food into the small intestine, blunting post-meal blood sugar spikes.
- Appetite and satiety: Acting on receptors in the brain, tirzepatide increases feelings of fullness and reduces appetite, which contributes to the body weight reductions observed in clinical trials including SURMOUNT-1 (Jastreboff AM et al., N Engl J Med, 2022).
Because both GIP and GLP-1 receptor activation are glucose-dependent, insulin is only released when blood sugar is elevated, which limits the risk of hypoglycemia when tirzepatide is used without insulin or sulfonylureas, per FDA labeling.
Side Effects by Week
| Time Period | Common Side Effects | What Helps |
|---|---|---|
| Weeks 1–2 (2.5 mg starting dose) |
Nausea (reported in up to 18% of patients in SURPASS-2), decreased appetite, mild injection-site reactions (redness, itching), fatigue | Eat smaller, bland meals; avoid high-fat foods immediately after injection; rotate injection sites per FDA labeling guidance |
| Weeks 3–4 (still at 2.5 mg or first titration) |
Nausea may persist or increase, vomiting (reported in up to 6% in SURPASS-2), diarrhea, constipation, abdominal discomfort | Stay well hydrated; eat slowly; avoid lying down immediately after meals; track bowel habits to discuss with prescriber |
| Months 2–3 (dose escalation phase) |
Gastrointestinal symptoms typically peak during dose increases (per FDA label); dyspepsia, belching, gastroesophageal reflux | Dose escalation is intentionally gradual (every 4 weeks per labeling) to allow GI tolerance; antacids may be discussed with prescriber |
| Long-term (Month 4 onward) |
GI side effects generally decrease at stable doses per SURPASS-1 trial data; hair thinning (telogen effluvium associated with rapid weight loss, noted in SURMOUNT-1); injection-site bruising | Adequate protein intake supports hair health; consistent injection technique reduces site reactions; regular lab monitoring per prescriber schedule |
Most Common Side Effects
- Nausea: The most frequently reported adverse reaction across SURPASS clinical trials, occurring in up to 18% of participants at the 15 mg dose in SURPASS-2 (Frías JP et al., N Engl J Med, 2021).
- Diarrhea: Reported in up to 17% of patients at the 15 mg dose in SURPASS-2; typically mild to moderate in severity per FDA labeling.
- Decreased appetite: Noted consistently across SURPASS and SURMOUNT trial populations; contributes to observed weight reduction per study data.
- Vomiting: Reported in up to 6% of tirzepatide-treated patients in SURPASS-2; most common during dose escalation periods per FDA label.
- Constipation: Reported in up to 6% of patients across SURPASS trials; linked to slowed gastric motility per FDA labeling mechanism description.
- Abdominal pain: Reported in approximately 6% of patients in SURPASS trials; typically described as mild cramping or bloating per trial adverse event reporting.
- Dyspepsia (indigestion): Reported at lower frequencies across the SURPASS program; associated with slowed gastric emptying per FDA-approved prescribing information.
- Injection-site reactions: Including redness, bruising, and itching at the site of subcutaneous injection; reported across all SURPASS trials per FDA labeling.
- Hypoglycemia: Risk is low when tirzepatide is used as monotherapy; however, the FDA label warns of increased risk when combined with insulin or sulfonylurea agents.
Serious Side Effects
- ⚠️ BOXED WARNING — Thyroid C-Cell Tumors: The FDA prescribing information carries a Boxed Warning stating that tirzepatide caused thyroid C-cell tumors in rodents at clinically relevant exposures; it is unknown whether tirzepatide causes thyroid C-cell tumors, including medullary thyroid carcinoma (MTC), in humans. Mounjaro is contraindicated in patients with a personal or family history of MTC or in patients with Multiple Endocrine Neoplasia syndrome type 2 (MEN 2), per FDA labeling.
- ⚠️ Pancreatitis: Acute pancreatitis, including fatal and non-fatal hemorrhagic or necrotizing pancreatitis, has been reported with GLP-1 receptor agonists; FDA labeling advises discontinuation if pancreatitis is suspected.
- ⚠️ Hypersensitivity reactions: Serious hypersensitivity reactions including anaphylaxis and angioedema have been reported with tirzepatide per FDA labeling; patients experiencing such reactions should discontinue use immediately.
- ⚠️ Acute kidney injury: Cases of acute kidney injury and worsening of chronic renal failure have been reported, often in the setting of severe dehydration from nausea, vomiting, or diarrhea, per the FDA-approved prescribing information.
- ⚠️ Diabetic retinopathy complications: In SURPASS-2, worsening of diabetic retinopathy was reported; patients with a history of diabetic retinopathy should be monitored per FDA label guidance.
- ⚠️ Severe hypoglycemia (with concomitant agents): FDA labeling recommends dose reduction of concomitant insulin secretagogues or insulin when initiating tirzepatide to reduce hypoglycemia risk.
- ⚠️ Gastroparesis / severe GI disease: Tirzepatide has not been studied in patients with severe GI disease, including severe gastroparesis; FDA labeling does not recommend use in this population.
Managing Side Effects
Nausea
Nausea is the most commonly reported side effect across the SURPASS clinical trial program. Per FDA labeling, the graduated dose-escalation schedule (starting at 2.5 mg for 4 weeks before any increase) is specifically designed to reduce GI tolerability issues. Strategies frequently discussed in clinical contexts and consistent with trial management protocols include eating smaller portions, choosing low-fat and low-odor foods, avoiding eating too quickly, and timing injections on days when activity levels are lower. Persistent or severe nausea lasting beyond the initial titration period should be reported to a prescriber, as dose escalation may be delayed per FDA labeling instructions.
Diarrhea and Constipation
Both diarrhea and constipation were reported in SURPASS trials as opposing GI manifestations. Diarrhea risk may be reduced by avoiding high-fiber or high-fat foods during dose escalation. Constipation, linked to slowed gastric motility per FDA labeling, may be managed through adequate fluid intake and dietary fiber. Severe or prolonged diarrhea carries a risk of dehydration, which FDA labeling associates with acute kidney injury; fluid replacement is important.
Vomiting
Vomiting was reported in up to 6% of patients in SURPASS-2 at the 15 mg dose. If vomiting prevents adequate fluid or food intake, prescribers may consider pausing dose escalation per the FDA label's titration guidance. Severe or repeated vomiting accompanied by abdominal pain should be evaluated promptly to rule out pancreatitis, per FDA labeling warnings.
Injection-Site Reactions
Per FDA prescribing information, tirzepatide is administered subcutaneously in the abdomen, thigh, or upper arm. Rotating injection sites with each weekly dose reduces localized skin reactions such as redness, bruising, and itching. Injecting into areas of lipohypertrophy (thickened skin from repeated injections at the same site) should be avoided, as this can affect absorption consistency.
Hypoglycemia
Per FDA labeling, tirzepatide alone carries a low inherent risk of hypoglycemia because its insulin-stimulating action is glucose-dependent. However, when combined with insulin or sulfonylureas, the FDA label recommends reducing the dose of those agents at initiation to minimize hypoglycemia risk. Patients on combination regimens should be familiar with hypoglycemia symptoms (shakiness, sweating, confusion) and have a plan for glucose correction.
Hair Thinning
Hair thinning, or telogen effluvium, was reported in the SURMOUNT-1 trial (Jastreboff AM et al., N Engl J Med, 2022) and is understood to be associated with rapid weight loss rather than a direct drug effect. It is typically temporary. Adequate dietary protein intake is generally consistent with recommendations for patients experiencing this effect, though patients should discuss specific nutritional needs with their care team.
Cost and Access in 2026
Cash Price (Without Insurance)
As of early 2026, the list price for Mounjaro is approximately $1,069–$1,100 per month for a four-pen supply, varying by pharmacy and dose strength. Cash prices may differ by retailer and region. GoodRx and similar discount programs may offer reduced prices at participating pharmacies; actual savings vary.
Eli Lilly Savings Program
Eli Lilly offers the Mounjaro Savings Card for commercially insured, eligible patients, which may reduce monthly out-of-pocket costs significantly. A separate program exists for uninsured or underinsured patients. Eligibility criteria apply and are defined by Lilly; patients can enroll at the manufacturer's website or through their prescriber's office. Income thresholds and insurance status affect eligibility.
Insurance Coverage Notes
Coverage for Mounjaro varies widely by insurance plan and indication. As of 2026, many commercial plans cover tirzepatide for its FDA-approved indication of type 2 diabetes management, though prior authorization requirements are common. Medicare Part D coverage depends on individual plan formularies. Mounjaro is FDA-approved only for type 2 diabetes; use for weight management is addressed under a separate brand name (Zepbound, also tirzepatide, FDA-approved for chronic weight management in 2023).
Compounded Tirzepatide
During periods of FDA-declared shortage, compounding pharmacies produced tirzepatide-containing preparations. The FDA removed tirzepatide from its drug shortage list in 2024, which affected the legal status of compounded tirzepatide. As of 2026, patients and prescribers should verify current FDA shortage and compounding status directly through FDA.gov, as regulations have continued to evolve.
Frequently Asked Questions
What doses is Mounjaro available in?
Per FDA labeling, Mounjaro is available as single-dose autoinjector pens in six strengths: 2.5 mg/0.5 mL, 5 mg/0.5 mL, 7.5 mg/0.5 mL, 10 mg/0.5 mL, 12.5 mg/0.5 mL, and 15 mg/0.5 mL. The recommended starting dose is 2.5 mg once weekly for four weeks, then increased to 5 mg once weekly, with optional further titration in 2.5 mg increments every four weeks as needed and tolerated, up to a maximum of 15 mg once weekly.
How is Mounjaro injected?
Per FDA prescribing information, Mounjaro is administered as a subcutaneous injection once weekly, on the same day each week, at any time of day, with or without meals. Approved injection sites are the abdomen, thigh, or upper arm. Injection sites should be rotated with each dose. Mounjaro should not be injected intravenously or intramuscularly.
How much weight loss occurred in clinical trials?
In the SURMOUNT-1 trial (Jastreboff AM et al., N Engl J Med, 2022), which studied tirzepatide in adults with obesity or overweight without type 2 diabetes, participants receiving 15 mg achieved a mean body weight reduction of approximately 20.9% at 72 weeks compared to 3.1% with placebo. In SURPASS-2 (Frías JP et al., N Engl J Med, 2021), which studied patients with type 2 diabetes, weight reductions of up to 12.4 lb (5.6 kg) at 5 mg and up to 25.2 lb (11.4 kg) at 15 mg were observed at 40 weeks versus semaglutide 1 mg comparator.
Who should not take Mounjaro?
Per FDA labeling, Mounjaro is contraindicated in patients with: (1) a personal or family history of medullary thyroid carcinoma (MTC); (2) Multiple Endocrine Neoplasia syndrome type 2 (MEN 2); and (3) known serious hypersensitivity to tirzepatide or any excipients in the formulation. FDA labeling also advises against use in patients with severe GI disease including severe gastroparesis, and notes the drug has not been studied in patients with a history of pancreatitis.
Can Mounjaro be used during pregnancy?
Per FDA labeling, Mounjaro is not recommended during pregnancy. Adequate human data on tirzepatide use in pregnancy are not available. Animal reproduction studies showed adverse effects on fetal development at doses resulting in exposures below the maximum recommended human dose. FDA labeling recommends discontinuing Mounjaro at least two months before a planned pregnancy due to the long washout period.
What is the difference between Mounjaro and Zepbound?
Both Mounjaro and Zepbound contain the same active ingredient, tirzepatide, and are manufactured by Eli Lilly. The distinction is solely in FDA-approved indication: Mounjaro is approved for type 2 diabetes management (FDA approval May 2022, NDA 215866), while Zepbound is approved for chronic weight management in adults with obesity or overweight with at least one weight-related condition (FDA approval November 2023). Dosing strengths and the route of administration are the same for both products.
How does Mounjaro compare to semaglutide (Ozempic)?
The SURPASS-2 trial (Frías JP et al., N Engl J Med, 2021) directly compared tirzepatide to semaglutide 1 mg in adults with type 2 diabetes. Participants on tirzepatide 10 mg and 15 mg achieved greater reductions in HbA1c (−2.01% and −2.30% respectively) compared to semaglutide 1 mg (−1.86%) at 40 weeks. Greater weight reductions were also observed with tirzepatide 15 mg (−11.4 kg) versus semaglutide 1 mg (−5.7 kg). Mechanistically, tirzepatide acts on both GIP and GLP-1 receptors per FDA labeling, whereas semaglutide acts on GLP-1 receptors only per its FDA labeling.
Does Mounjaro reduce cardiovascular risk?
The SURPASS-CVOT trial (ClinicalTrials.gov NCT04255433), conducted by Eli Lilly, evaluated cardiovascular outcomes with tirzepatide. Results published in 2024 (Eli Lilly press release and subsequent peer-reviewed publication) demonstrated that tirzepatide met its primary cardiovascular endpoint by showing non-inferiority and subsequent superiority compared to placebo for major adverse cardiovascular events (MACE) in adults with type 2 diabetes and established cardiovascular disease. Patients should discuss cardiovascular risk and trial data specifics with their prescriber.