Semaglutide vs. Tirzepatide vs. Retatrutide — Head-to-Head (2026)
Three GLP-1 receptor agonists, three different mechanisms, three different positions in the regulatory pipeline. Here's how they actually compare in mechanism, weight loss, side-effect profile, dosing, and approval status — without marketing.
The head-to-head table
| Dimension | Semaglutide | Tirzepatide | Retatrutide |
|---|---|---|---|
| Brand names | Ozempic, Wegovy, Rybelsus | Mounjaro, Zepbound | None (investigational) |
| Drug class | GLP-1 receptor agonist | Dual GLP-1 / GIP receptor agonist | Triple GLP-1 / GIP / glucagon receptor agonist |
| Mechanism | GLP-1 alone | GLP-1 + GIP for synergistic incretin effect | GLP-1 + GIP + glucagon (glucagon component may raise energy expenditure) |
| FDA approval (2026) | Yes (Ozempic, Wegovy, Rybelsus) | Yes (Mounjaro, Zepbound) | No — Phase 3 trials ongoing |
| Average weight loss (highest-dose pivotal trial) | ~14.9% at 68 weeks (STEP-1) | ~22.5% at 72 weeks (SURMOUNT-1, 15 mg) | ~24% at 48 weeks (Phase 2, 12 mg) |
| Dosing frequency | Weekly subcutaneous (or daily oral for Rybelsus) | Weekly subcutaneous | Weekly subcutaneous (in trials) |
| Common side effects | Nausea, diarrhea, constipation, fatigue (worst in first 4 weeks) | Nausea, diarrhea, decreased appetite (slightly more nausea than semaglutide in head-to-head) | Nausea, GI side effects similar to GLP-1 class; long-term profile not yet established |
| Boxed warning | Thyroid C-cell tumors | Thyroid C-cell tumors | Same class warning expected |
| Available at NHWL? | Yes — compounded | Yes — compounded | No |
| NHWL cash price | $166/mo (90-day program) | $233/mo (90-day program) | — |
How to read the weight-loss numbers
The headline trial numbers (14.9% / 22.5% / 24%) are average body weight loss in the highest-dose arm at the trial endpoint. They are not what every patient experiences. Real-world ranges:
- Roughly 60–70% of patients lose 10%+ of body weight.
- Roughly 35–50% lose 15%+.
- Roughly 10–15% are minimal responders (less than 5% loss).
- Tirzepatide tends to produce larger average loss than semaglutide in head-to-head and adjusted comparisons.
Higher does not always mean better-for-you. Some patients tolerate semaglutide much better and end up with more sustained loss because they stay on therapy longer.
Side-effect profile in our clinic
Across our 5,400+ patients, the typical experience:
- Weeks 1–4: mild-to-moderate nausea on dose-escalation days. Resolves with hydration, smaller meals, slower titration.
- Weeks 4–12: appetite reduction stabilizes; energy improves once nausea fades.
- Persistent issues: ~5–8% of patients have ongoing GI symptoms severe enough to consider stopping. We try dose reduction first; switching agents second.
- Rare but serious: pancreatitis, gallbladder issues, severe gastroparesis, suicidal ideation. We screen for risk factors and stop therapy at any sign.
How we choose between semaglutide and tirzepatide
The honest framework we use during consults:
- Start with semaglutide if: gentler side-effect profile preferred, type 2 diabetes management is a primary concern, lower starting cost matters, comorbid GI sensitivity.
- Start with tirzepatide if: higher target weight loss (BMI 40+), prior poor response to semaglutide, willingness to manage moderate nausea, want maximum effect at one molecule.
- Switch within protocol if response plateaus on semaglutide and the patient has tolerated it well — about 30% of plateaued patients re-engage weight loss after switching.
Frequently asked questions
What is the difference between semaglutide and tirzepatide?
Semaglutide targets GLP-1 receptors only; tirzepatide is a dual agonist targeting both GLP-1 and GIP. In trials, tirzepatide produces somewhat greater average weight loss (up to 22.5% in SURMOUNT-1) than semaglutide (up to 14.9% in STEP-1). Both are weekly subcutaneous injections. Side-effect profiles overlap; tirzepatide has slightly more nausea reported in head-to-head data.
Is retatrutide better than tirzepatide?
Phase 2 trials suggest larger numerical weight loss for retatrutide (~24% at 48 weeks). However, retatrutide is investigational and not FDA-approved as of 2026. We do not currently dispense retatrutide outside of clinical trial enrollment.
Which GLP-1 should I take?
It depends on your medical history, tolerance, goals, and budget. Most patients start with semaglutide; some switch to tirzepatide if response plateaus. Your physician should make the call after reviewing your history.
How fast does each drug work?
Most patients notice reduced appetite and food noise within 1–2 weeks. The full effect builds over months. STEP-1 showed 14.9% body weight loss at week 68; SURMOUNT-1 (tirzepatide 15 mg) showed 22.5% at week 72.
What about Ozempic vs. Wegovy?
Both are semaglutide. Ozempic is FDA-approved for type 2 diabetes; Wegovy is FDA-approved for chronic weight management. Same molecule, different labels and slightly different maximum doses. Mounjaro and Zepbound have the same relationship for tirzepatide.
This page is informational only and not medical advice. Speak with a licensed physician before starting any GLP-1 therapy. Individual results vary. Trial data referenced (STEP-1, SURMOUNT-1, retatrutide Phase 2) are publicly available in peer-reviewed publications. Brand names referenced (Ozempic®, Wegovy®, Rybelsus® — Novo Nordisk; Mounjaro®, Zepbound® — Eli Lilly) are registered trademarks of their respective companies. New Hope Weight Loss is not affiliated with, endorsed by, or sponsored by these companies. Compounded medications are not FDA-approved products.