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Peptide library · Metabolic

Tirzepatide

A synthetic peptide that activates both GIP and GLP-1 receptors. Compounded tirzepatide is not FDA-approved, although FDA-approved versions exist and have been studied in large controlled human trials.

Last reviewed September 22, 2026

The short version

Tirzepatide is a lab-made chain of 39 amino acids designed to signal through two incretin receptors, GIP and GLP-1. Its evidence base is unusual for this library: it includes receptor and mouse experiments, early human pharmacology, and large randomized trials in adults with metabolic disease or obesity.

FDA-approved versions exist, but compounded tirzepatide is not FDA-approved. Whether a compounded preparation has a place in someone’s care is a decision for a licensed provider based on that person’s medical needs.

What it is

Tirzepatide is a synthetic incretin-mimetic peptide. It is built from the backbone of glucose-dependent insulinotropic polypeptide, or GIP, and engineered to activate both the GIP receptor and the glucagon-like peptide-1 receptor. A fatty-acid side chain helps it bind albumin in the blood. It is not a naturally circulating human peptide, although the two hormone systems it copies are part of normal gut signaling.

Researchers first called it LY3298176. It has 39 amino acids, a molecular formula of C225H348N48O68, a molecular weight of 4,813.53 daltons and CAS number 2023788-19-2. The discovery paper described its receptor activity in cells, findings in mice and an early human program involving 142 participants.1

Where the research stands

Tirzepatide has laboratory, animal and extensive human evidence. The controlled trials establish findings for the FDA-approved drug products and the populations studied. They do not establish that a compounded preparation is identical in quality, stability or clinical performance.

How far the evidence has climbed

  1. Cell studiesYesReceptor signaling and pancreatic-islet experiments
  2. Animal studiesYesMetabolic research in mice
  3. Small human pilotsYesEarly pharmacology and proof-of-concept studies
  4. Controlled human trialsYesLarge randomized phase 3 programs
  5. Compounded preparationNot approvedSeparate FDA-approved products exist

Here is what some of the most-cited studies looked at. Each names its species, because a result in a mouse is not a result in a person.

  • CellsMiceHumans2018

    From discovery to first human studies

    The paper reported receptor assays, mouse measurements of glucose and food intake, and early studies involving 142 healthy adults and adults with type 2 diabetes. It did not test a compounded preparation.1

  • Cells2020

    Two receptors, uneven signaling

    Receptor and mouse-islet experiments compared engagement of the GIP and GLP-1 receptors and measured their signaling patterns. They did not test patient outcomes or a compounded preparation.2

  • Humans2020

    Gastric-emptying pharmacology

    A phase 1 study measured gastric emptying during treatment with an investigational tirzepatide trial product. It did not test a compounded preparation.3

  • Humans2021

    Type 2 diabetes trial

    An open-label randomized trial enrolled 1,879 adults with type 2 diabetes and measured glycated hemoglobin, body weight and adverse events. It tested manufactured trial products, not compounded tirzepatide.4

  • Humans2022

    Obesity trial

    A double-blind randomized trial enrolled 2,539 adults without diabetes who had obesity, or overweight with a weight-related condition. It measured body-weight change and adverse events against placebo and did not test compounded tirzepatide.5

  • Review2023

    Pooled safety signals

    A meta-analysis combined nine randomized trials covering 9,871 people and compared pancreatitis and gallbladder or biliary events. It summarized trial products, not compounded preparations.6

What the research can’t tell you

  • Approved and compounded are different

    The trials studied manufactured drug products, not every compounded preparation. They cannot verify the identity, stability or quality of a particular compounded vial.

  • Common tolerability limits

    Across the controlled program, gastrointestinal events were common and sometimes led participants to stop treatment.45

  • A rodent thyroid finding

    The FDA label carries a boxed warning based on thyroid C-cell tumors in rodents. Whether that finding predicts the same risk in humans is unknown.7

  • Specific safety questions remain

    Gallbladder and biliary events appear as a pooled signal, while the pancreatitis estimate remains imprecise. A meta-analysis cannot settle every rare or long-term risk.6

Compounded tirzepatide and FDA status

FDA-approved versions exist; compounded tirzepatide is not FDA-approved

FDA-approved tirzepatide products exist. Compounded tirzepatide is a different regulatory category: FDA does not review a compounded drug’s safety, effectiveness or quality before it is marketed.8

FDA confirmed the national tirzepatide injection shortage was resolved on December 19, 2024.9 FDA says section 503A restricts compounding drugs that are essentially copies of commercially available products regularly or in inordinate amounts; section 503B has a separate framework.10

Those regulatory facts do not turn approved-product evidence into evidence for a compounded preparation. Promise Peptides is currently taking waitlist sign-ups. Joining is not a medical request and no prescription comes from it.

A prescription route

Promise is currently accepting waitlist signups. Joining is not a treatment request and does not result in a prescription. If treatment visits open, any treatment request would require clinical review; prescribing and pharmacy fulfillment would remain separate decisions.

  1. Start on Promise’s tirzepatide page

    It shows what the treatment involves and its current availability.

  2. Answer the tirzepatide questionnaire

    A licensed provider reviews health history, medicines and goals, and can decline. Not everyone qualifies.

  3. Pharmacy review is a separate step

    A prescription does not guarantee preparation or dispensing. A pharmacy must separately determine whether it can fulfill the prescription under the applicable requirements.

A prescription does not turn compounded tirzepatide into an FDA-approved product; it means a clinician reviewed the individual case and made the prescribing decision.

Tirzepatide at Promise

Read the treatment information and view the current waitlist.

Join the Promise waitlist

Peak may earn money when readers become Promise patients.

Joining does not guarantee future treatment availability. Availability would depend on the treatment, state, clinical review and separate pharmacy review.

Questions

Is tirzepatide a peptide?

Yes. It is a synthetic chain of 39 amino acids with a fatty-acid side chain. Its design is based on the GIP hormone backbone.1

Is tirzepatide a GLP-1?

It is a GLP-1 receptor agonist, but not only that. It also activates the GIP receptor, which is why researchers call it a dual incretin agonist.2

Is compounded tirzepatide FDA-approved?

No. FDA-approved versions exist, but a compounded preparation does not carry FDA approval and is not reviewed by FDA before marketing.8

Sources

  1. Coskun T, et al. LY3298176, a novel dual GIP and GLP-1 receptor agonist for the treatment of type 2 diabetes mellitus: from discovery to clinical proof of concept. Mol Metab. 2018. PubMed 30473097
  2. Willard FS, et al. Tirzepatide is an imbalanced and biased dual GIP and GLP-1 receptor agonist. JCI Insight. 2020. PubMed 32730231
  3. Urva S, et al. The novel dual glucose-dependent insulinotropic polypeptide and glucagon-like peptide-1 receptor agonist tirzepatide transiently delays gastric emptying. Diabetes Obes Metab. 2020. PubMed 32519795
  4. Frias JP, et al. Tirzepatide versus semaglutide once weekly in patients with type 2 diabetes. N Engl J Med. 2021. PubMed 34170647
  5. Jastreboff AM, et al. Tirzepatide once weekly for the treatment of obesity. N Engl J Med. 2022. PubMed 35658024
  6. Zeng Q, et al. Safety issues of tirzepatide in type 2 diabetes and obesity: a systematic review and meta-analysis. Front Endocrinol. 2023. PubMed 37908750
  7. U.S. Food and Drug Administration. Tirzepatide injection prescribing information. 2022.
  8. U.S. Food and Drug Administration. Compounding and the FDA: Questions and Answers. Content current as of September 16, 2025.
  9. U.S. Food and Drug Administration. Declaratory Order: Resolution of Shortages of Tirzepatide Injection Products. December 19, 2024.
  10. U.S. Food and Drug Administration. Compounding when drugs are on FDA’s drug shortages list.