Comparison
Ozempic vs Mounjaro
The two most prescribed weight loss drugs compared. Same weekly injection, different mechanisms. Mounjaro hits two receptors instead of one — and the data shows it.
The Short Answer
Mounjaro (tirzepatide) produces more weight loss than Ozempic (semaglutide) — ~21% vs ~15% in trials — and causes less nausea. The only advantage Ozempic has is cardiovascular outcomes data (the SELECT trial) and an oral formulation (Rybelsus).
| Ozempic / Wegovy | Mounjaro / Zepbound | |
|---|---|---|
| Generic name | Semaglutide | Tirzepatide |
| Manufacturer | Novo Nordisk | Eli Lilly |
| Weight loss brand | Wegovy | Zepbound |
| Diabetes brand | Ozempic | Mounjaro |
| Mechanism | GLP-1 receptor agonist | Dual GIP + GLP-1 receptor agonist |
| Mean weight loss | ~15% (STEP 1, 68 weeks) | ~21% (SURMOUNT-1, 72 weeks) |
| Head-to-head winner | — | Tirzepatide (SURPASS-2) |
| Max dose | 2.4 mg/week (Wegovy) | 15 mg/week (Zepbound) |
| Injection frequency | Once weekly | Once weekly |
| Oral option | Yes (Rybelsus — diabetes only) | No (oral version in trials) |
| Nausea rate | ~44% | ~31% |
| HbA1c reduction | Up to 1.8% | Up to 2.4% |
| Cardiovascular data | SELECT: 20% MACE reduction | SURPASS-CVOT: ongoing |
| FDA approved for weight | Yes (Wegovy, 2021) | Yes (Zepbound, 2023) |
| FDA approved for diabetes | Yes (Ozempic, 2017) | Yes (Mounjaro, 2022) |
| Supply issues | Ongoing shortages | Intermittent shortages |
Why Mounjaro Produces More Weight Loss
Ozempic activates one receptor (GLP-1). Mounjaro activates two (GIP + GLP-1). The GIP receptor adds insulin sensitivity benefits and appears to improve tolerability — Mounjaro causes less nausea than Ozempic despite producing more weight loss. The dual mechanism also seems to reduce appetite more effectively.
In the only head-to-head trial (SURPASS-2), tirzepatide 15 mg produced significantly more weight loss than semaglutide 1 mg in type 2 diabetes patients. While the semaglutide dose in that trial wasn't the maximum weight-loss dose, the trend is consistent across all data.
Where Ozempic Still Wins
Cardiovascular outcomes. The SELECT trial showed Ozempic reduces major cardiovascular events by 20% in overweight/obese adults — the first GLP-1 drug to prove cardiovascular benefit independent of diabetes. Mounjaro's cardiovascular outcomes trial (SURPASS-CVOT) is still running.
Ozempic also has an oral formulation (Rybelsus) for diabetes, making it the only GLP-1 agonist available as a pill. Mounjaro is injection-only for now.
Side Effects
Both cause gastrointestinal side effects (nausea, vomiting, diarrhea), primarily during dose escalation. Mounjaro has a somewhat better GI profile — about 31% nausea vs Ozempic's 44%. Both carry the same class warnings (thyroid tumors in animals, pancreatitis risk, gallbladder events).
Cost and Insurance
Both cost approximately $1,000-1,300/month without insurance. Coverage varies significantly by insurer and indication. Getting coverage for weight loss (Wegovy/Zepbound) is harder than for diabetes (Ozempic/Mounjaro). Supply shortages have been an ongoing issue for both drugs.
What About Retatrutide?
Eli Lilly's next drug, Retatrutide, adds a third receptor (glucagon) and showed 24% weight loss in Phase 2. It's not available yet — still in Phase 3 trials. If approved, it would likely surpass both Ozempic and Mounjaro. See the full three-way comparison.