Independent dose, titration, and reconstitution reference for the four FDA-approved GLP-1 receptor agonists plus their compounded counterparts. Every page links the matching ASCEND calculator so you can run the math for any vial size or dose.
All four FDA-approved GLP-1 agonists work through the same core mechanism (GLP-1 receptor activation; tirzepatide adds GIP receptor activation). Differences come down to FDA indication, maximum maintenance dose, pen form factor, and trial outcomes:
Highest weight loss in published trials: Zepbound (tirzepatide), ~20.9% mean at 72 weeks.
Highest weight loss for a GLP-1 mono-agonist: Wegovy (semaglutide), ~14.9% mean at 68 weeks.
Strongest T2D HbA1c effect: Mounjaro (tirzepatide), 2.0 to 2.5 percentage point reduction.
For the compounded versions of semaglutide and tirzepatide that researchers reconstitute from lyophilized vials with bacteriostatic water, ASCEND provides vial-size-aware calculators and concentration tables.
A GLP-1 receptor agonist is a peptide drug that mimics glucagon-like peptide-1, a gut hormone released after eating. By activating GLP-1 receptors in pancreatic beta cells and hypothalamic satiety centers, these drugs improve glucose-dependent insulin secretion, slow gastric emptying, and suppress appetite. Approved indications include Type 2 diabetes and chronic weight management.
Which GLP-1 produces the most weight loss?
In head-to-head trial data, tirzepatide (Zepbound, Mounjaro) produces greater mean weight loss than semaglutide (Wegovy, Ozempic) at maximum tolerated doses. Tirzepatide is a dual GIP and GLP-1 agonist; the GIP component appears to drive additional weight reduction. SURMOUNT-1 reported about 20.9% mean weight loss with Zepbound 15 mg; STEP-1 reported about 14.9% with Wegovy 2.4 mg.
How long does it take to reach the target GLP-1 dose?
Semaglutide titration spans 16 to 20 weeks from first injection to the 2.4 mg maintenance dose. Tirzepatide titration spans 21 or more weeks to reach the 15 mg maintenance dose. Each step is typically four weeks. Slower titration reduces the severity of GI side effects.
What is the difference between Wegovy and Ozempic?
Both contain the same active molecule, semaglutide. Wegovy is FDA-approved for chronic weight management at a 2.4 mg maintenance dose. Ozempic is FDA-approved for Type 2 diabetes with a maintenance range up to 2.0 mg per week. Pen strengths and labeling differ.
Is compounded semaglutide still available?
The FDA declared the semaglutide shortage resolved in early 2025, restricting routine 503A compounding. Compounded semaglutide may still be available for individual patient prescriptions where a clinical reason justifies a non-approved formulation, but the broad shortage-driven supply has narrowed. Always verify the pharmacy and Certificate of Analysis.
How do I calculate the draw volume for a compounded GLP-1 dose?
For compound semaglutide at the standard 5 mg vial plus 1 mL bacteriostatic water reconstitution (5 mg/mL), divide the dose in mg by 5 to get mL, then multiply by 100 for the IU mark on a U-100 insulin syringe. Example: 0.25 mg / 5 = 0.05 mL = 5 IU. Open the semaglutide calculator at /calc/semaglutide/ for any vial size.
For research informational use only. Not medical advice. All brand names referenced are trademarks of their respective owners and are used for editorial identification only. Consult a qualified healthcare provider before any clinical decision.
Calculate your exact draw volume
Enter your vial size and BAC water to get precise IU markings for any semaglutide or tirzepatide dose.