Semaglutide and tirzepatide are the two GLP-1 medications that dominate the 2026 weight-management conversation. They are not interchangeable. The choice depends on three things: how much weight you need to lose, how well you tolerate gastrointestinal side effects, and what you can sustainably afford to spend.
The short answer
Semaglutide (sold as Wegovy when branded for weight loss, Ozempic when branded for diabetes, and as compounded semaglutide through 503A pharmacies) is the older, better-studied option with the larger long-term safety dataset. Tirzepatide (sold as Zepbound for weight loss and Mounjaro for diabetes) is newer, produces somewhat larger average weight loss in trials, and tends to cost more.
How they differ
- Semaglutide is a GLP-1 receptor agonist. It mimics the glucagon-like peptide-1 hormone, which slows gastric emptying and reduces appetite signaling.
- Tirzepatide is a dual GIP/GLP-1 receptor agonist. It activates the same GLP-1 pathway and a second hormone pathway (GIP), which appears to amplify the appetite-reduction effect.
The dual-mechanism action is the leading hypothesis for why tirzepatide produces larger average weight loss in head-to-head trials. It is also why some patients report a stronger gastrointestinal adjustment period in the first weeks.
Efficacy data
The peer-reviewed trial data published through late 2025 shows the following average loss at 72 weeks of treatment:
- Semaglutide 2.4mg weekly — approximately 15% of starting body weight.
- Tirzepatide 15mg weekly — approximately 22% of starting body weight.
Both numbers are averages. Real-world results in our reader survey skew slightly lower than trial numbers, primarily because real patients escalate the dose more cautiously than trial protocols.
Side-effect profile
The two medications share most of their side-effect profile: nausea, constipation or diarrhea, fatigue in the first weeks of dose escalation, occasional injection-site soreness. Tirzepatide users in our survey were marginally more likely to report stronger nausea during dose escalation; semaglutide users were marginally more likely to report constipation.
For week-by-week management, see our GLP-1 side-effects survival guide.
Cost in 2026
Pricing in 2026 is split sharply by whether the medication is branded or compounded:
- Branded Wegovy / Zepbound, self-pay: roughly $1,000–$1,300 per month at maintenance dose.
- Branded with insurance + manufacturer savings card: as low as $25–$199 per month for eligible patients.
- Compounded semaglutide (503A): roughly $199–$349 per month.
- Compounded tirzepatide (503A): roughly $349–$499 per month, with availability tightening in 2026.
For a complete pricing breakdown including hidden fees, see what GLP-1 telehealth actually costs.
Which one for which patient
There is no universal “better.” Our research-based guidance based on 2026 data:
- Lower BMI, modest goal (15–30 lbs): semaglutide is usually sufficient and easier on the budget.
- Higher BMI, larger goal (40+ lbs): tirzepatide’s larger average loss is meaningful enough to justify the higher cost for many patients.
- Strong GI sensitivity history: semaglutide first; the slower mechanism activation tends to be more tolerable.
- Insurance covers branded: the medication your plan covers is the right one to start with.