Tirzepatide is a once-weekly subcutaneous injection developed by Eli Lilly and Company. It is the first dual incretin agonist — activating both GLP-1 and GIP receptors. SURMOUNT-1 demonstrated 22.5% mean body weight loss at the 15 mg dose over 72 weeks, the highest weight loss reported for any approved or investigational GLP-1 medication.
Tirzepatide is a once-weekly subcutaneous injection developed by Eli Lilly and Company. It is the first dual incretin agonist — activating both GLP-1 and GIP receptors. SURMOUNT-1 demonstrated 22.5% mean body weight loss at the 15 mg dose over 72 weeks, the highest weight loss reported for any approved or investigational GLP-1 medication.
Manufacturer / source: Mounjaro, Zepbound, compounded
For tirzepatide forms head-to-head, see comparison page. For trial data, see clinical research.
Tirzepatide is the active ingredient in Mounjaro (FDA-approved for type 2 diabetes, May 2022) and Zepbound (FDA-approved for chronic weight management, November 2023). Compounded tirzepatide is a non-FDA-approved alternative formulation that proliferated during the 2022–2024 shortage period.
Tirzepatide is the first-in-class dual GIP and GLP-1 receptor agonist. By activating both the glucose-dependent insulinotropic polypeptide (GIP) receptor and the glucagon-like peptide-1 (GLP-1) receptor, tirzepatide produces synergistic effects on insulin secretion, glucagon suppression, gastric emptying, and central appetite signaling. The dual mechanism is the leading hypothesis for why tirzepatide outperforms GLP-1 monoagonists in head-to-head trials.
In the SURMOUNT-1 trial (NEJM 2022), participants without diabetes on the 15 mg dose lost a mean 20.9% of body weight at 72 weeks versus 3.1% on placebo. The SURPASS-2 trial (NEJM 2021) directly compared tirzepatide to semaglutide 1 mg in type 2 diabetes; all three tirzepatide doses (5, 10, 15 mg) produced greater A1C and weight reductions. SURMOUNT-OSA (2024) showed reductions in apnea-hypopnea index, contributing to Zepbound's December 2024 FDA approval for moderate-to-severe obstructive sleep apnea in adults with obesity.
Standard titration begins at 2.5 mg subcutaneously once weekly for four weeks, increasing in 2.5 mg increments every four weeks as tolerated to a maintenance dose of 5, 10, or 15 mg weekly. Slower titration is often used to reduce gastrointestinal adverse events. Injections are administered into the abdomen, thigh, or upper arm.
The most common adverse events are gastrointestinal: nausea, diarrhea, vomiting, constipation, and dyspepsia, typically peaking during titration and improving with continued use. The FDA boxed warning addresses thyroid C-cell tumor risk based on rodent studies; tirzepatide is contraindicated in patients with personal or family history of medullary thyroid carcinoma or Multiple Endocrine Neoplasia syndrome type 2. Reports of pancreatitis, gallbladder disease, acute kidney injury (often dehydration-mediated), and severe hypersensitivity reactions appear in post-marketing surveillance.
Brand-name Zepbound list price is approximately $1,060–$1,100 per month in 2026; with Eli Lilly's self-pay vial program for select doses, costs fall to $399–$549 for some patients. Commercial insurance coverage for chronic weight management remains inconsistent. Medicare does not cover GLP-1s for weight loss as of 2026. Compounded tirzepatide from licensed 503A and 503B pharmacies typically prices between $159–$399 per month depending on dose and provider, though availability narrowed significantly following FDA shortage-resolution declarations in 2024.
In the head-to-head SURPASS-2 trial, all three doses of tirzepatide produced greater A1C reductions and greater weight loss than semaglutide 1 mg in adults with type 2 diabetes. Indirect comparisons of SURMOUNT-1 (tirzepatide) and STEP-1 (semaglutide) suggest tirzepatide produces larger absolute weight loss in obesity populations, though direct head-to-head obesity trials are limited.
Compounded tirzepatide became significantly restricted after the FDA declared the shortage resolved in late 2024. Some 503A and 503B pharmacies continue to provide patient-specific compounded formulations under narrow regulatory pathways, often combining tirzepatide with additional ingredients to qualify as a personalized formulation. Confirm with your provider that any compounded product comes from a licensed, inspected pharmacy.
Current FDA labeling positions tirzepatide as a long-term therapy. The SURMOUNT-4 extension trial showed that discontinuing tirzepatide led to substantial weight regain over the following 52 weeks, supporting clinical guidance to view it as chronic treatment for chronic disease rather than a short course.
Mounjaro for type 2 diabetes is widely covered by commercial insurance and many state Medicaid plans, though prior authorization is common. Zepbound for weight management has more limited coverage; some commercial plans cover it with BMI and comorbidity criteria, while Medicare currently does not cover GLP-1s for weight loss.
Compounded semaglutide + tirzepatide · MD/DO oversight
*12-month plan · flat rate · all titration doses
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