Mounjaro and Ozempic are both once-weekly injections approved for type 2 diabetes, but they contain different drugs. Mounjaro is tirzepatide, which activates the GIP and GLP-1 receptors. Ozempic is semaglutide, which activates GLP-1 only. In head-to-head trials, tirzepatide lowered blood sugar and weight more than semaglutide. Neither Mounjaro nor Ozempic is approved for weight loss; their weight-management versions are Zepbound and Wegovy.
Mounjaro vs Ozempic: side-by-side comparison
| Ozempic | Mounjaro | |
|---|---|---|
| Active ingredient | Semaglutide | Tirzepatide |
| Maker | Novo Nordisk | Eli Lilly |
| Approved use (US) | Type 2 diabetes: blood sugar control; lower cardiovascular risk in adults with type 2 diabetes and heart disease; lower kidney and cardiovascular risk in adults with type 2 diabetes and chronic kidney disease | Type 2 diabetes: blood sugar control (adults and ages 10+); lower major cardiovascular events in adults with type 2 diabetes at high risk |
| Mechanism | GLP-1 receptor agonist | GIP and GLP-1 receptor agonist |
| Schedule | Once weekly; 0.25 mg for 4 weeks, then 0.5 mg; steps to 1 mg, then 2 mg if needed, each after at least 4 weeks | Once weekly; 2.5 mg start; increase in 2.5 mg steps after at least 4 weeks, up to 15 mg |
| Form | Pen (prefilled syringe also listed) | Pen, vial or KwikPen |
| Weight-management version | Wegovy (semaglutide) | Zepbound (tirzepatide) |
Sources: Ozempic prescribing information (sections 1, 2.2, 3, 12.1); Mounjaro prescribing information (sections 1, 2.1, 3, 12.1); Wegovy and Zepbound labels. Your prescriber chooses the dose path.
What the head-to-head trials show
In type 2 diabetes. SURPASS-2 was a 40-week trial in 1,879 adults with type 2 diabetes comparing tirzepatide 5, 10 or 15 mg with semaglutide 1 mg. HbA1c fell by 2.01, 2.24 and 2.30 percentage points with tirzepatide versus 1.86 with semaglutide, and body weight fell more with tirzepatide (1.9, 3.6 and 5.5 kg more than semaglutide, respectively). Nausea, diarrhea and vomiting were the most common adverse events in both groups (NEJM 2021, PubMed).
In obesity without diabetes. This compares the weight-management products at their top doses, not Mounjaro and Ozempic. SURMOUNT-5 was a 72-week open-label trial of 751 adults. The average weight change was -20.2% with tirzepatide (10 or 15 mg) and -13.7% with semaglutide (1.7 or 2.4 mg) (NEJM 2025, PubMed). Both trials were funded by Lilly, which makes tirzepatide.
Trial averages don’t predict your own result. If weight is your goal, ask your prescriber about Wegovy or Zepbound rather than a diabetes brand, and see Zepbound vs Wegovy for that comparison.
Side effects
Both labels list the same core group: nausea, vomiting, diarrhea, abdominal pain and constipation for Ozempic, and nausea, diarrhea, decreased appetite, vomiting, constipation, dyspepsia and abdominal pain for Mounjaro (reported by 5% or more of patients). Both carry a boxed warning about thyroid C-cell tumors seen in rodents and are contraindicated with a personal or family history of medullary thyroid carcinoma or MEN 2. Both list pancreatitis, gallbladder disease, low blood sugar with insulin or sulfonylureas, and diabetic retinopathy complications as precautions. Mounjaro’s label also advises women on oral contraceptives to add a barrier method or switch to a non-oral one for 4 weeks after starting and after each dose increase.
Never change or switch doses on your own, and tell your prescriber about severe or lasting symptoms. More in GLP-1 side effects: what to expect and how to manage them.
Missed doses
Ozempic’s label says to take a missed dose within 5 days; Mounjaro’s says within 4 days (96 hours). After that, skip it and resume on the usual day. Follow your own prescriber’s instructions.
How to choose
You don’t choose between them on your own: it depends on your diagnosis, other medicines, tolerance and what your insurer covers. Questions worth bringing to an appointment:
- Is my goal blood sugar, weight, or both, and which approved product fits it?
- How long will I stay on each dose step?
- What should I do about nausea, and when should I call?
For single-drug background, see Ozempic vs Wegovy, our tirzepatide overview and semaglutide guide.
Tracking either drug
With either medicine, a log of injection day, dose, side effects, meals and weight helps you and your prescriber see what is happening at each step. Mingo is a GLP-1 tracker for iPhone and Android that logs shots, food and protein, side effects and weight in one place. It doesn’t replace your doctor. Get the app.
Key takeaways
- Mounjaro (tirzepatide) and Ozempic (semaglutide) are both approved for type 2 diabetes, not for weight loss.
- Tirzepatide acts on GIP and GLP-1 receptors; semaglutide on GLP-1 only.
- In SURPASS-2, tirzepatide lowered HbA1c and weight more than semaglutide 1 mg; in SURMOUNT-5 (weight-management doses), tirzepatide led to more weight loss than semaglutide.
- Side effects overlap: mainly nausea, vomiting, diarrhea and constipation, plus the same boxed thyroid warning.
Frequently asked questions
What is the main difference between Mounjaro and Ozempic?
The active ingredient. Mounjaro contains tirzepatide, which activates GIP and GLP-1 receptors; Ozempic contains semaglutide, which activates the GLP-1 receptor. Both are weekly injections approved for type 2 diabetes.
Which works better for weight loss, Mounjaro or Ozempic?
Neither is approved for weight loss. In the SURPASS-2 diabetes trial, weight fell more with tirzepatide than with semaglutide 1 mg. For weight management, the comparable products are Zepbound and Wegovy, and in the SURMOUNT-5 trial tirzepatide produced more weight loss than semaglutide.
Do Mounjaro and Ozempic have the same side effects?
Largely, yes: digestive symptoms are the most common for both, and both carry a boxed warning about thyroid tumors seen in rodents. Details differ, so read each label with your prescriber.
Can I switch from Ozempic to Mounjaro?
Only with your prescriber, who decides the starting dose and timing. Don’t use two GLP-1 medicines at once; the labels of the weight-management versions say combining them is not recommended.
How should I track my progress on either one?
Log each dose, side effects, meals and weight, and bring that record to your appointments.
