The Fundamental Difference
Ozempic (semaglutide 1mg) is a GLP-1 receptor agonist — it activates one receptor pathway.
Mounjaro (tirzepatide) is a dual GLP-1 and GIP receptor agonist — it activates two receptor pathways simultaneously. This dual mechanism is why Mounjaro produces greater average weight loss.
Both medications are weekly subcutaneous injections. Both reduce appetite, improve blood sugar control, and produce meaningful metabolic benefits. The choice between them depends on your clinical goals, comorbidities, tolerance, and what you can afford in the Australian healthcare system.
Weight Loss Comparison
The SURMOUNT-5 trial — the first head-to-head comparison of the two medications — found tirzepatide achieved approximately 20% body weight reduction versus approximately 14% for semaglutide at 72 weeks.
In practical terms: a person weighing 100kg would expect to lose approximately 20kg on Mounjaro versus approximately 14kg on Ozempic over 18 months on average.
Individual results vary significantly. Some patients respond better to one medication than the other regardless of average trial results. Genetics, baseline weight, adherence, diet, and physical activity all influence outcomes. Your GP may recommend starting one medication and switching if response is inadequate.
Liver Health Comparison
Both improve liver health, primarily through weight loss and improved insulin sensitivity. The clinical differences matter if you have fatty liver disease or MASH.
Ozempic/Wegovy (semaglutide): Has the most mature liver-specific evidence base. The ESSENCE trial demonstrated 62.9% MASH resolution at 72 weeks with semaglutide 2.4mg. The TGA provisionally approved Wegovy specifically for MASH treatment in April 2026. Ozempic at 1mg provides lower-magnitude but meaningful liver benefit.
Mounjaro (tirzepatide): Phase 2 liver data is positive — significant liver fat reduction and enzyme improvement. Phase 3 SYNERGY-NASH trial results expected in 2026 will provide definitive data. Greater weight loss on average suggests greater liver fat reduction.
For established MASH needing treatment now: Wegovy has TGA approval. Mounjaro does not yet.
For weight management with comorbid fatty liver: Either is appropriate, with Mounjaro potentially providing greater liver fat reduction due to superior weight loss.
Ozempic and fatty liver — full guide →
Australian Availability and Cost
| Ozempic | Mounjaro | |
|---|---|---|
| TGA approved for | Type 2 diabetes | Weight management |
| PBS listed? | Yes — T2D only ($31.60) | No — private only |
| Private cost | $120–$180/month (T2D PBS) | $285–$690/month |
| Referral needed | GP prescription | GP prescription |
| Availability | Widely available | Available — some shortages |
For patients with type 2 diabetes, Ozempic is significantly more accessible due to PBS subsidy. For weight management without diabetes, Mounjaro may provide greater results but at higher cost.
Wegovy (semaglutide 2.4mg) sits between the two for weight loss potency and is the TGA-approved option for MASH. See our Wegovy and fatty liver guide for the liver-specific pathway.
Side Effects — What's Different
Both share the same GLP-1 class gastrointestinal side effects — nausea, vomiting, diarrhoea, constipation — predominantly during dose escalation. These typically improve after the first 4–8 weeks.
Mounjaro may produce more intense early GI side effects consistent with its greater potency and more significant weight loss — though individual experience varies widely.
Both carry a class warning for thyroid C-cell tumours based on animal studies — not directly observed in humans at therapeutic doses.
Both are associated with increased gallstone risk — approximately 27% higher than non-GLP-1 users based on meta-analysis data.
Which Should You Choose?
Choose Ozempic if:
- You have type 2 diabetes (PBS subsidised)
- Cost is a primary consideration
- You have confirmed MASH needing the TGA-approved treatment (Wegovy at 2.4mg specifically)
- You have not tolerated Mounjaro previously
Choose Mounjaro if:
- Weight loss magnitude is the primary goal
- You do not have type 2 diabetes and are paying privately regardless
- You have not responded adequately to semaglutide
- Your liver disease is MASLD at early stages (awaiting SYNERGY-NASH data before MASH-specific choice)
Discuss with your GP. These medications have different clinical profiles that interact with your individual metabolic picture, other medications, and health history. Baseline liver assessment with FIB-4 and elastography is recommended for all GLP-1 patients with metabolic risk factors.
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Frequently asked questions
Is Mounjaro stronger than Ozempic?
Mounjaro produces greater average weight loss (20% vs 14%) due to its dual GLP-1/GIP mechanism. For liver health, it is expected to produce greater liver fat reduction — but semaglutide has more mature MASH-specific trial data and the only current TGA approval for liver disease.
Can I switch from Ozempic to Mounjaro?
Yes — with your GP's guidance. The switch is typically straightforward with appropriate dose titration. If switching for liver health reasons, discuss whether Wegovy (higher-dose semaglutide) under the new TGA MASH indication might be more appropriate.
Which has fewer side effects — Ozempic or Mounjaro?
Both share the same GLP-1 class GI side effects. Mounjaro may produce more intense early effects consistent with its greater potency. Individual experience varies.
Is Mounjaro better for fatty liver than Ozempic?
Both improve fatty liver. Mounjaro produces more weight loss on average, which drives greater liver fat reduction. Semaglutide has more mature MASH-specific evidence and TGA approval for liver disease. The SYNERGY-NASH results (2026) will provide the head-to-head liver histology comparison.
Related reading
Sources: SURMOUNT-5 trial NEJM (May 2025); ESSENCE trial NEJM (May 2025); TGA approvals; PBAC December 2025; Australian pricing data (May 2026).
This article is for educational purposes only. It does not constitute medical advice. Always consult your GP or a specialist about your individual health circumstances.
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