Effectiveness: Mounjaro wins on weight loss
Clinical trial data consistently shows Mounjaro producing more weight loss than Wegovy:
- Mounjaro (SURMOUNT-1): ~21% average body weight loss at the highest dose (15mg) over 72 weeks. Over half of participants lost 20%+ of their body weight.
- Wegovy (STEP-1): 14.9% average body weight loss at 2.4mg over 68 weeks. About one-third lost 20%+.
The difference is clinically meaningful. For a 100kg person, Mounjaro would produce approximately 21kg of weight loss vs 15kg with Wegovy on average. However, these are averages — some people respond better to one than the other, and a head-to-head trial comparing them directly has not been published.
Mounjaro's advantage is believed to come from its dual mechanism — targeting both GLP-1 and GIP receptors. The GIP pathway may enhance fat metabolism and energy expenditure beyond what GLP-1 alone achieves.
Cardiovascular benefits: Wegovy wins on heart data
Wegovy has a major advantage in cardiovascular evidence. The SELECT trial — involving over 17,000 participants followed for up to 5 years — showed a 20% reduction in major adverse cardiovascular events (heart attack, stroke, cardiovascular death) in patients with obesity and established heart disease.
This is landmark data. No other weight loss medication has demonstrated direct cardiovascular risk reduction in a large outcomes trial. It's the primary reason Wegovy is being considered for PBS listing.
Mounjaro's cardiovascular outcomes trial (SURPASS-CVOT) is ongoing. The results haven't been published yet. If positive, it could shift the balance significantly.
Cost comparison
Both medications are in a similar price range on private prescription:
| Wegovy | Mounjaro | |
|---|---|---|
| Private cost/month | $400–$460 | $350–$500 |
| Annual cost | ~$4,800–$5,500 | ~$4,200–$6,000 |
| PBS potential | Pending ($31.60/script if listed) | No prospect currently |
If Wegovy gets PBS listed, it becomes dramatically cheaper for eligible patients — $31.60/script vs $400–460 private. This would make Wegovy the clear winner on cost for those who qualify.
Side effects comparison
Both cause similar gastrointestinal side effects, but at different rates:
- Nausea: Wegovy ~44% vs Mounjaro ~29% — Mounjaro is noticeably better tolerated
- Diarrhoea: Similar rates (~30%)
- Vomiting: Wegovy ~24% vs Mounjaro ~12%
- Constipation: Similar rates (~24%)
Mounjaro's lower nausea and vomiting rates are a meaningful advantage for tolerability. However, Mounjaro has a longer dose escalation period (20 weeks vs 16), so the adjustment period extends longer overall.
Which telehealth providers prescribe both?
Several Australian telehealth providers prescribe both Wegovy and Mounjaro, allowing you to discuss the choice during your consultation:
- Juniper — prescribes both
- Hub Health — prescribes both
Can you switch between them?
Yes. If you start on one and it's not working well (insufficient weight loss, intolerable side effects), your doctor can switch you to the other. You'll typically need to restart dose escalation when switching, even if you were at a high dose of the previous medication.
Guide to switching medications →
Our assessment
For most people, this comes down to priorities:
- If maximum weight loss is your goal: Mounjaro produces ~21% average weight loss vs ~15-17% for Wegovy. If you want the most effective option, Mounjaro has the edge.
- If you have heart disease or cardiovascular risk: Wegovy is the only medication with proven CV risk reduction (SELECT trial), and it may be PBS-subsidised for this group.
- If cost is a major factor: They're similar on private pricing. But if you qualify for PBS, Wegovy becomes dramatically cheaper.
- If you're worried about nausea: Mounjaro has lower nausea rates (~29% vs ~44%).
Neither choice is wrong. Both are excellent medications that represent a genuine step change in obesity treatment. The best choice depends on your individual health circumstances, priorities, and what your doctor recommends.