Mounjaro (tirzepatide) and Ozempic (semaglutide) are the two most prescribed once-weekly injectables for type 2 diabetes. Both lower A1c, both cause weight loss, both have a boxed thyroid warning. The differences matter.
Effectiveness — head-to-head
SURPASS-2 directly compared the two over 40 weeks in patients with T2D inadequately controlled on metformin:
| Outcome | Mounjaro (15 mg) | Ozempic (1 mg) |
|---|---|---|
| A1c reduction | −2.30% | −1.86% |
| Weight loss | −11.2 kg | −5.7 kg |
| A1c < 5.7% (normal range) | 51% of patients | 20% |
Mounjaro won on every glycemic and weight endpoint. (Note: a higher 2 mg Ozempic dose was approved later, narrowing the gap modestly.)
Why Mounjaro wins
Tirzepatide hits both GLP-1 and GIP receptors. The dual mechanism appears to enhance insulin sensitivity and weight loss beyond what a pure GLP-1 like semaglutide can achieve.
Where Ozempic still has a role
- Cardiovascular outcomes data. Ozempic has established CV benefit (SUSTAIN-6); tirzepatide’s CV trial (SURPASS-CVOT) is pending.
- Longer real-world experience. More clinician familiarity, more data on edge cases.
- Cost. Modest list-price advantage (~$969 vs ~$1,069), though both are usually similarly priced after insurance.
Side effects
Roughly comparable. Both cause nausea, diarrhea, and constipation in 20–40% of users during titration. Some real-world reports suggest tirzepatide may be slightly better tolerated dose-for-dose, but the difference is small.
Which should you take?
- Highest A1c reduction needed: Mounjaro.
- Existing cardiovascular disease: Ozempic (proven CV outcomes today).
- Weight loss is a major secondary goal: Mounjaro.
- Whichever your formulary covers: Both are defensible first-line choices.
See also
- Mounjaro full review
- Ozempic full review
- Zepbound vs Wegovy — same molecules, weight-loss indication.
- Ozempic vs Wegovy — same molecule (semaglutide), two labels.
- ADA Standards of Care 2024 — current T2D treatment guidelines.
- Compare every GLP-1 side-by-side.