Semaglutide vs tirzepatide: how they differ
Semaglutide and tirzepatide are the two most-discussed weight-management medications today. They are related, but they are not the same drug. Understanding the difference helps you have a more useful conversation with a provider.
The mechanism difference
Semaglutide is a GLP-1 receptor agonist. It mimics one hormone — glucagon-like peptide-1 — and amplifies the signals around blood sugar, appetite, and stomach emptying.
Tirzepatide is a dual GIP/GLP-1 receptor agonist. It activates GLP-1 receptors and also GIP (glucose-dependent insulinotropic polypeptide) receptors. GIP is another gut hormone involved in metabolism. In trials, the dual action appears to produce somewhat greater weight loss on average than GLP-1 alone, though individual responses vary.
The brand names
- Semaglutide: Ozempic (type 2 diabetes), Wegovy (weight management), and oral Rybelsus (diabetes).
- Tirzepatide: Mounjaro (type 2 diabetes), Zepbound (weight management).
The same active ingredient is sold under different brand names depending on the FDA-approved indication. Coverage rules often vary by brand even when the active ingredient is identical.
Dosing
Both are once-weekly subcutaneous injections at most dose levels. Both follow a titration schedule — providers start low and increase the dose over weeks to months to give your body time to adjust to GLP-1 effects on the stomach and appetite.
For weight management, Wegovy doses range up to 2.4 mg weekly. Zepbound doses range up to 15 mg weekly. The numbers are not directly comparable across the two medications because they're different molecules.
What the trials showed
In published clinical trials for chronic weight management, the average weight loss after roughly a year was approximately:
- Semaglutide 2.4 mg weekly: around 15% of starting body weight
- Tirzepatide 15 mg weekly: around 20–22% of starting body weight
These are averages across trial populations. Some participants lost much more, others much less, and some discontinued due to side effects. Trial conditions are more structured than real life.
Side effects
The two medications share a similar side-effect profile because both work through GLP-1. The most common complaints are gastrointestinal: nausea, constipation, diarrhea, and reflux. These typically peak during dose increases and improve over weeks. Less common but more serious considerations include pancreatitis, gallbladder issues, and contraindications related to personal or family history of medullary thyroid cancer or MEN2. A clinician will screen for these.
Choosing between them
Patients rarely choose freely between the two. The choice is usually shaped by:
- Insurance coverage and formulary tier. Your plan may cover one and not the other, or require step therapy through one before approving the other.
- Provider preference and experience. Some clinicians start with semaglutide because it has been in use longer; others go straight to tirzepatide when it's available.
- Tolerability. Some people respond to one with fewer side effects than the other. Switching is possible but requires re-titration.
- Cost. Cash prices are similar, but manufacturer savings programs differ.
What about compounded versions?
Some telehealth clinics offer compounded semaglutide or tirzepatide. These are not FDA-approved versions; they are made by compounding pharmacies and operate under different rules. Quality and dosing accuracy can vary by pharmacy. The FDA has issued safety statements about compounded GLP-1s. WeightWise does not sell compounded medications. Discuss the trade-offs with a licensed clinician.