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Approved drugFDA-approved

Tirzepatide

The most-searched peptide in the US. An FDA-approved prescription drug, marketed as Mounjaro and Zepbound.

Part 1Header & identifiers

Also known as: Marketed as Mounjaro and Zepbound. Class: GLP-1 / metabolic.

Class
Dual GIP and GLP-1 receptor agonist
Brands
Mounjaro (type 2 diabetes, NDA 215866); Zepbound (weight management and obstructive sleep apnea, NDA 217806)
Route studied
Once-weekly subcutaneous injection
Developer
Eli Lilly

Last reviewed 3 Nov 2026 by The Peptide Informative editorial team. Found an error? Tell us; see our corrections policy.

Part 2Status at a glance

FDAApproved prescription drug. Zepbound is indicated, with a reduced-calorie diet and increased physical activity, to reduce excess body weight and maintain weight reduction long term in adults with obesity, or overweight with at least one weight-related condition, and to treat moderate to severe obstructive sleep apnea in adults with obesity [3].
Boxed warningTirzepatide causes thyroid C-cell tumors in rats. Contraindicated with a personal or family history of medullary thyroid carcinoma or MEN 2 [3].
Enforcement newsNamed in multiple 2026 FDA warning letters to online sellers of unapproved “research” products [4].
SportCheck the current WADA Prohibited List.

Status checked 3 Nov 2026. Regulations changed several times in 2026, so check the linked sources for updates.

Part 3Evidence grade

Approved drug

Large, randomized phase 3 trials published in the New England Journal of Medicine, plus FDA approval for specific indications.

Evidence comes from large randomized human trials, so we don't show an animal-versus-human breakdown. How we grade evidence.

Part 4What it is

Tirzepatide is a synthetic peptide that activates two gut-hormone receptors: glucose-dependent insulinotropic polypeptide (GIP) and glucagon-like peptide-1 (GLP-1). Trials give it as a once-weekly injection under the skin [1].

Part 5What studies found

Weight in adults without diabetes (SURMOUNT-1)

In a phase 3, double-blind trial, 2,539 adults with obesity (or overweight with a weight-related condition) and no diabetes were randomized to weekly tirzepatide 5, 10 or 15 mg, or placebo, for 72 weeks. Mean weight change was −15.0%, −19.5% and −20.9% on the three doses, versus −3.1% on placebo. A 20% or greater reduction occurred in 50% (10 mg) and 57% (15 mg) of participants, versus 3% on placebo [1].

Blood sugar in type 2 diabetes, compared with semaglutide (SURPASS-2)

In an open-label, 40-week phase 3 trial, 1,879 adults with type 2 diabetes were randomized to tirzepatide 5, 10 or 15 mg or semaglutide 1 mg. HbA1c fell by 2.01, 2.24 and 2.30 percentage points on tirzepatide, versus 1.86 on semaglutide. All tirzepatide doses were noninferior and superior to semaglutide 1 mg, and weight reductions were also greater [2].

Part 6Doses used in published studies

Not a recommendationThese are doses reported in published studies, listed with their population, route and duration so readers can understand the research. They are not instructions, and they say nothing about safety for you. Talk to a licensed clinician.
StudyPopulationRouteDose studiedDurationMain result
SURMOUNT-1 [1]2,539 adults with obesity or overweight, no diabetesSubcutaneous, once weekly5, 10 or 15 mg72 weeks−15.0% to −20.9% vs −3.1% body weight
SURPASS-2 [2]1,879 adults with type 2 diabetesSubcutaneous, once weekly5, 10 or 15 mg vs semaglutide 1 mg40 weeksHbA1c −2.01 to −2.30 vs −1.86 points

For an approved drug, dosing is set by the prescriber under the FDA label [3]. The trial doses above are listed only so readers can understand the studies.

Part 7Safety & adverse events

  • In SURMOUNT-1, the most common adverse events were gastrointestinal, mostly mild to moderate and mainly during dose escalation. Adverse events led to stopping treatment in 4.3%, 7.1% and 6.2% on the three doses, versus 2.6% on placebo [1].
  • In SURPASS-2, nausea occurred in 17–22% on tirzepatide (18% on semaglutide), and serious adverse events in 5–7% (3% on semaglutide) [2].
  • The FDA label lists common adverse reactions including nausea, diarrhea, vomiting, constipation, abdominal pain, injection site reactions, fatigue, hypersensitivity reactions and hair loss. It also notes serious hypersensitivity reactions, including anaphylaxis and angioedema [3].
Report side effectsSuspected side effects can be reported to FDA MedWatch.

Part 8What is unknown

  • The FDA label states it is unknown whether tirzepatide causes thyroid C-cell tumors in humans [3].
  • Trial results apply to the approved product used in the trial populations. They tell you nothing about products sold outside the regulated supply chain [4].

Part 9Community discussion

Tirzepatide will have its own moderated category when our forum opens. Personal experiences there are labeled as anecdotes, and claims about research must link a source.

Join the forum waitlist

Part 10References

  1. Jastreboff AM, et al. Tirzepatide Once Weekly for the Treatment of Obesity (SURMOUNT-1). N Engl J Med. 2022;387(3):205-216. PubMed 35658024 · doi:10.1056/NEJMoa2206038
  2. Frías JP, et al. Tirzepatide versus Semaglutide Once Weekly in Patients with Type 2 Diabetes (SURPASS-2). N Engl J Med. 2021;385(6):503-515. PubMed 34170647 · doi:10.1056/NEJMoa2107519
  3. Eli Lilly and Company. Zepbound (tirzepatide) prescribing information. DailyMed, U.S. National Library of Medicine. DailyMed
  4. ArentFox Schiff. RUO-ined: Five Peptide Vendors Learn “Research Use Only” Is Not a Legal Strategy. 18 Sep 2026. afslaw.com
Educational information onlyThis profile summarizes published research. It is not medical advice and does not recommend using Tirzepatide. Full medical disclaimer.