What it is
Tirzepatide is a dual GLP-1/GIP receptor agonist, sold under the brand names Mounjaro for type 2 diabetes and Zepbound for weight loss. GLP-1 and GIP are both incretin hormones, hormones the gut releases after eating that influence insulin release and appetite; tirzepatide is built to activate both receptors at once rather than just one, which distinguishes it from single-receptor GLP-1 medicines like semaglutide.
In the PeptidesAI encyclopedia, tirzepatide is categorized under weight management alongside semaglutide and cagrilintide. It is also available as a compounded, lyophilized powder in vials, separate from the branded pens, for research or off-label use.
How it's thought to work
By activating both the GLP-1 and GIP receptors, tirzepatide is studied for producing greater appetite suppression, improved insulin signaling, and greater fat metabolism than agonists that act on only one of these receptors. Combining both pathways is the proposed reason it has shown stronger effects in trials than single-receptor GLP-1 medicines, since GIP is thought to add an insulin-sensitizing effect on top of the appetite and gastric-emptying effects that GLP-1 alone provides.
What the research says
The SURMOUNT clinical trials showed body weight reduction of up to 22.5% among study participants, a larger figure than reported for single-receptor GLP-1 agonists in comparable trials. On this evidence the FDA has approved tirzepatide as Mounjaro for type 2 diabetes and as Zepbound for weight loss.
Reported side effects
The gastrointestinal side effect profile is similar to other GLP-1-class medicines: nausea, vomiting, and diarrhea are the most commonly reported. Injection site reactions have also been reported. Combining tirzepatide with insulin raises the risk of hypoglycemia (low blood sugar).
Reconstitution
The branded pens sold as Mounjaro and Zepbound come pre-filled and ready to use; they are not reconstituted by the patient. This page instead covers the lyophilized tirzepatide powder sold in 5 mg, 10 mg, 15 mg, and 30 mg vials, which is typically reconstituted with bacteriostatic (BAC) water before use.
Worked example. A 10 mg vial is 10,000 mcg. Reconstituted with 2 mL of BAC water, that works out to 10,000 mcg ÷ 2 mL = 5,000 mcg/mL. On a U-100 insulin syringe, where each unit is 0.01 mL, each unit holds 5,000 × 0.01 = 50 mcg. Use the peptide reconstitution calculator to work out the concentration and units for any vial size and water volume.
Important notes
Tirzepatide is an FDA-approved prescription medicine, sold as Mounjaro and Zepbound. The powder vials discussed here are compounded or research-grade products, separate from those branded pens, and are not themselves FDA-approved products.
Frequently asked questions
These questions cover the same ground as the sections above, in a shorter format.
What is tirzepatide?
A dual GLP-1/GIP receptor agonist sold as Mounjaro for type 2 diabetes and Zepbound for weight loss, both FDA-approved.
How is tirzepatide thought to work?
It activates both GLP-1 and GIP receptors together, which research links to greater appetite suppression, improved insulin signaling, and fat metabolism than single-receptor agonists.
What does the research on tirzepatide say?
The SURMOUNT trials showed body weight reduction of up to 22.5%, evidence that supported FDA approval as Mounjaro and Zepbound.
What are the reported side effects of tirzepatide?
A GI profile similar to other GLP-1-class medicines, plus injection site reactions and, when combined with insulin, an increased risk of low blood sugar.
How much is one unit from a 10 mg Tirzepatide vial?
With 2 mL of BAC water, a 10 mg vial is 5,000 mcg/mL, so one unit on a U-100 syringe (0.01 mL) holds 50 mcg.
The full entry, plus the calculator
The PeptidesAI app has the complete encyclopedia entry for Tirzepatide — one of 70 compounds covered — plus the reconstitution calculator, a dose log and reminders. Free to download on iPhone.
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