Mounjaro vs Wegovy vs Ozempic: the key differences.
Three brand names, two molecules, one drug class. Mounjaro is tirzepatide; Wegovy and Ozempic are both semaglutide at different doses for different conditions. This explainer covers how each works, what the TGA has registered them for, what the trials found, how side effects compare and where each sits on the PBS. It is meant to help you understand a conversation with your doctor, not replace it.
Mounjaro (tirzepatide) acts on two gut-hormone receptors, GIP and GLP-1; Wegovy and Ozempic (semaglutide) act on GLP-1 only. In Australia, Mounjaro is registered for type 2 diabetes and chronic weight management, Wegovy for chronic weight management and cardiovascular risk reduction, Ozempic for type 2 diabetes only. In the head-to-head SURMOUNT-5 trial, tirzepatide produced a greater average weight reduction than semaglutide (−20.2% vs −13.7% at 72 weeks). None is PBS-listed for weight management as of 1 October 2026. Which, if any, suits you is a clinical decision for your prescriber.
- 10 September 2024 — TGA registers Mounjaro for chronic weight management, alongside type 2 diabetes. TGA registration.
- 19 December 2024 — TGA adds a cardiovascular risk-reduction indication to Wegovy (established cardiovascular disease, BMI ≥27, no diabetes). RACGP newsGP.
- 3 June 2025 — TGA adds class-wide warnings about aspiration during anaesthesia or deep sedation. TGA safety update.
- 18 July 2025 — Ozempic removed from the TGA medicine shortage list. Novo Nordisk Australia.
- 28 April 2026 — Eli Lilly declines a PBS listing of Mounjaro for type 2 diabetes after the PBAC's 11 March 2026 recommendation. PBS medicine status: tirzepatide.
- 23 July 2026 — TGA updates all GLP-1 medicines for the rare optic nerve condition NAION. TGA safety update.
Mounjaro, Wegovy and Ozempic side by side.
Figures are from each product's Australian Product Information and the trials below; only SURMOUNT-5 compared the molecules directly.
| Feature | Mounjaro | Wegovy | Ozempic |
|---|---|---|---|
| Active ingredient | Tirzepatide (Eli Lilly) | Semaglutide (Novo Nordisk) | Semaglutide (Novo Nordisk) |
| Mechanism | Dual GIP and GLP-1 receptor agonist | GLP-1 receptor agonist | GLP-1 receptor agonist |
| TGA indications (adults) | Type 2 diabetes; chronic weight management (BMI ≥30, or ≥27 with a weight-related condition) | Chronic weight management (BMI ≥30, or ≥27 with a weight-related condition; adolescents 12+); cardiovascular risk reduction in established CVD, BMI ≥27, no diabetes | Type 2 diabetes only |
| Dosing | Weekly; 2.5 to 15 mg KwikPens in 2.5 mg steps; start 2.5 mg, step up at ≥4-week intervals; maintenance 5, 10 or 15 mg | Weekly; 0.25, 0.5, 1, 1.7, 2.4 mg pens; stepped up every 4 weeks over 16 weeks to 2.4 mg | Weekly; 0.25 mg start, 0.5 mg after 4 weeks, 1 mg if needed |
| Head-to-head | SURMOUNT-5: tirzepatide −20.2% vs semaglutide −13.7% at 72 weeks (751 adults, open-label) | Not studied | |
| PBS status (1 Oct 2026) | Not listed; sponsor declined T2D listing April 2026 | Not listed; PBAC recommended Nov 2025, price unresolved | Listed for type 2 diabetes only (Authority Required) |
One receptor or two.
GLP-1 and GIP are gut hormones released after eating. Both prompt insulin release when glucose rises; GLP-1 also slows stomach emptying, dampens glucagon and acts on appetite centres in the brain, which is why GLP-1 medicines reduce hunger.
Semaglutide (Wegovy, Ozempic) is a modified GLP-1 analogue with a half-life of about a week. Tirzepatide (Mounjaro) is a single molecule engineered to activate both the GIP and GLP-1 receptors; the added GIP activity is thought to contribute to its larger effects on weight and glucose. The shared GLP-1 action is why their side-effect lists overlap so heavily (see the semaglutide and tirzepatide food guides).
What the TGA has approved each one for.
Mounjaro
Type 2 diabetes in adults, alone or with other diabetes medicines. Chronic weight management from 10 September 2024 for adults with BMI ≥30, or ≥27 with a weight-related condition such as hypertension, sleep apnoea or prediabetes.
Wegovy
Chronic weight management in adults with BMI ≥30, or 27 to under 30 with a weight-related comorbidity; adolescents 12 and over since February 2024; and reduction of major cardiovascular events in adults with established cardiovascular disease and BMI ≥27 without diabetes, since December 2024.
Ozempic
Adults with insufficiently controlled type 2 diabetes, registered 28 August 2019. Doses of 0.25 mg (starting only), 0.5 mg and 1 mg weekly. Not registered for weight management; the same molecule at 2.4 mg is sold as Wegovy.
Prescribing outside a registered indication is lawful in Australia but a matter for the prescriber's judgment.
What the trials actually showed.
1,961 adults with BMI ≥30 (or ≥27 with a comorbidity), no diabetes, 68 weeks. Mean weight change −14.9% vs −2.4% with placebo. 86.4% vs 31.5% lost at least 5%. 4.5% vs 0.8% stopped because of gastrointestinal events. Funded by Novo Nordisk.
2,539 adults with BMI ≥30 (or ≥27 with a complication), no diabetes, 72 weeks. Mean weight change −15.0% (5 mg), −19.5% (10 mg), −20.9% (15 mg) vs −3.1% with placebo. 85% to 91% lost at least 5% vs 35%. Adverse events led to discontinuation in 4.3% to 7.1% vs 2.6%. Funded by Eli Lilly.
751 adults with obesity, no type 2 diabetes, 72 weeks, open-label. Tirzepatide 10 or 15 mg vs semaglutide 1.7 or 2.4 mg. Mean weight change −20.2% vs −13.7%; waist circumference −18.4 cm vs −13.0 cm. More tirzepatide participants reached each weight-loss threshold from 10% to 25%. Gastrointestinal events were the most common in both arms. Funded by Eli Lilly.
17,604 adults aged 45+ with established cardiovascular disease and BMI ≥27, no diabetes, mean follow-up 39.8 months. Cardiovascular death, heart attack or stroke in 6.5% on semaglutide vs 8.0% on placebo (hazard ratio 0.80, 95% CI 0.72 to 0.90). Adverse events led to permanent discontinuation in 16.6% vs 8.2%. Funded by Novo Nordisk.
These are group averages from selected trial populations who also received lifestyle support; individual results vary widely, weight tends to return after stopping, and no trial was designed to pick the right medicine for a particular person.
Side effects: more alike than different.
Frequencies follow the Australian PI convention: very common is at least 1 in 10, common 1 in 100 to 1 in 10, uncommon 1 in 1,000 to 1 in 100, rare 1 in 10,000 to 1 in 1,000.
| Category | Mounjaro (tirzepatide) | Wegovy (semaglutide 2.4 mg) | Ozempic (semaglutide ≤1 mg) |
|---|---|---|---|
| Very common | Nausea, diarrhoea, constipation, vomiting; hypoglycaemia when added to insulin or a sulfonylurea | Headache, nausea, vomiting, diarrhoea, constipation, abdominal pain, fatigue (nausea 43.9% vs 16.1% placebo) | Nausea (17.0% to 19.9%), diarrhoea (12.2% to 13.3%); hypoglycaemia with insulin or a sulfonylurea |
| Common | Abdominal pain, dyspepsia, bloating, burping, flatulence, reflux, decreased appetite, fatigue, injection-site reactions, hypersensitivity | Dizziness, gastritis, reflux, dyspepsia, burping, flatulence, bloating, gallstones, hair loss, injection-site reactions | Vomiting, abdominal pain, bloating, constipation, dyspepsia, reflux, burping, gallstones, fatigue, dizziness, retinopathy complications |
| Uncommon or rare | Gallstones, acute pancreatitis (uncommon) | Increased heart rate, acute pancreatitis (uncommon); anaphylaxis (rare) | Acute pancreatitis, delayed gastric emptying, increased heart rate (uncommon); anaphylaxis (rare) |
| Stopped for adverse events in trials | 4.3% to 7.1% vs 2.6% placebo (SURMOUNT-1) | 4.3% for gastrointestinal events (PI pooled trials) | 6.1% (0.5 mg) and 8.7% (1 mg) vs 1.5% placebo |
Class-wide precautions apply to all three: acute pancreatitis, gallbladder disease, dehydration leading to acute kidney injury, worsening diabetic retinopathy with rapid glucose improvement, aspiration under anaesthesia (TGA, 3 June 2025) and the rare optic nerve condition NAION (TGA, 23 July 2026). Mounjaro's PI adds that tirzepatide can reduce oral contraceptive absorption around initiation and dose increases (TGA advice, 1 December 2025). Rodent studies of both molecules found thyroid C-cell tumours; human relevance is unknown. For one product in depth, see Ozempic side effects.
Contraindications and cautions.
Each Australian PI lists one formal contraindication: hypersensitivity to the active ingredient or any excipient. Beyond that, both advise against use in type 1 diabetes, diabetic ketoacidosis, pregnancy (stop at least two months before trying to conceive) and end-stage kidney disease, with caution for past pancreatitis, severe gastrointestinal disease, insulin-treated diabetic retinopathy and severe liver impairment. The Australian PIs do not list a history of medullary thyroid cancer as a contraindication, though prescribers commonly consider it.
PBS status, and why the choice is clinical.
Ozempic is PBS-listed for type 2 diabetes under Authority Required criteria. Wegovy was recommended by the PBAC in November 2025 for established cardiovascular disease with BMI ≥35 (≥32.5 for Asian, Aboriginal or Torres Strait Islander people) but is unlisted while the price is negotiated. Mounjaro is unlisted after Eli Lilly declined the PBAC's type 2 diabetes terms in April 2026. See the Wegovy PBS explainer.
A prescriber weighs the condition being treated, cardiovascular history, kidney and liver function, other medicines, past gastrointestinal problems, pregnancy plans and tolerance of earlier doses, not just the biggest trial number. Your prescriber decides; a web page cannot. If you already take one, the Mounjaro diet plan, Wegovy diet plan and GLP-1 portion guide cover the food side.
What is the difference between Mounjaro and Wegovy?
Mounjaro contains tirzepatide, which activates both GIP and GLP-1 receptors. Wegovy contains semaglutide, which activates GLP-1 receptors only. Both are weekly injections registered by the TGA for chronic weight management; Mounjaro is also registered for type 2 diabetes, Wegovy also for cardiovascular risk reduction. In the head-to-head SURMOUNT-5 trial, tirzepatide produced a larger average weight reduction at 72 weeks.
Is Mounjaro stronger than Ozempic?
They are not directly comparable. Ozempic is semaglutide at up to 1 mg weekly, registered in Australia for type 2 diabetes, not weight management. Mounjaro is tirzepatide at 2.5 to 15 mg weekly, registered for both. Trials show greater average weight reduction with tirzepatide, but "stronger" is not a clinical goal; the right medicine depends on the condition, other health problems and tolerability.
What did SURMOUNT-5 show?
SURMOUNT-5 (NEJM 2025) randomised 751 adults with obesity but no type 2 diabetes to tirzepatide (10 or 15 mg) or semaglutide (1.7 or 2.4 mg) for 72 weeks. Mean weight change was −20.2% with tirzepatide and −13.7% with semaglutide; waist circumference fell 18.4 cm versus 13.0 cm. Gastrointestinal events were the most common adverse events in both groups. The trial was open-label and funded by Eli Lilly.
Do Mounjaro and Wegovy have the same side effects?
Largely yes. Both Australian PIs list nausea, diarrhoea, vomiting and constipation as very common, and both carry precautions for pancreatitis, gallbladder disease, dehydration and kidney injury, hypoglycaemia with insulin or sulfonylureas, retinopathy complications, aspiration under anaesthesia and the rare optic nerve condition NAION. Mounjaro's PI adds a precaution on oral contraceptive absorption.
Is Wegovy or Mounjaro on the PBS?
Neither, as of 1 October 2026. The PBAC recommended Wegovy in November 2025 for adults with established cardiovascular disease and BMI of 35 or more (32.5 for Asian, Aboriginal or Torres Strait Islander people), but the price is unresolved. The PBAC recommended Mounjaro for type 2 diabetes in March 2026; Eli Lilly declined the terms in April 2026. Ozempic is listed for type 2 diabetes only.
Can you switch from Ozempic or Wegovy to Mounjaro?
Any change between these medicines is a prescribing decision. They have different molecules, dose ladders and registered indications, and each Product Information describes starting low and stepping up. Preptide does not advise starting, stopping or switching medicines; your prescriber decides.
Who should not take Mounjaro or Wegovy?
Each Australian PI lists hypersensitivity to the active ingredient or any excipient as a contraindication. Neither should be used in type 1 diabetes, diabetic ketoacidosis or pregnancy (stop at least two months before conceiving), and both carry cautions for past pancreatitis, severe gastrointestinal disease, diabetic retinopathy and severe kidney or liver impairment. A prescriber weighs these for the individual.
Primary sources checked for this page.
- Aronne et al., Tirzepatide as Compared with Semaglutide for the Treatment of Obesity (SURMOUNT-5), NEJM 2025.
- Wilding et al., Once-Weekly Semaglutide in Adults with Overweight or Obesity (STEP 1), NEJM 2021.
- Jastreboff et al., Tirzepatide Once Weekly for the Treatment of Obesity (SURMOUNT-1), NEJM 2022.
- Lincoff et al., Semaglutide and Cardiovascular Outcomes in Obesity without Diabetes (SELECT), NEJM 2023.
- TGA AusPAR and Product Information: Mounjaro (tirzepatide), and the chronic weight management registration, 10 September 2024.
- TGA AusPAR and Product Information: Wegovy (semaglutide 2.4 mg).
- TGA AusPAR and Product Information: Ozempic (semaglutide).
- TGA safety update, 3 June 2025: anaesthesia and deep sedation warnings; 1 December 2025: contraception advice for Mounjaro; 23 July 2026: NAION class update.
- RACGP newsGP, 17 February 2025: Wegovy cardiovascular indication approved 19 December 2024.
- PBS medicine status: tirzepatide and PBS medicine status: semaglutide (Wegovy).
Editorial method: TGA-approved Product Information and TGA safety updates were checked first; peer-reviewed trial publications in the New England Journal of Medicine second, read from the published abstracts and results; PBS status pages for subsidy facts. Trial figures are quoted as published, with funding sources. Named clinical review is pending; this page has not yet been reviewed by an independent clinician. See the Preptide editorial policy for corrections and review standards.
Important: General information only, not medical advice. Wegovy and Ozempic are registered trademarks of Novo Nordisk; Mounjaro is a registered trademark of Eli Lilly. Preptide is independent and is not affiliated with, endorsed by or sponsored by either company. Preptide is food, not medication, and does not prescribe, sell, recommend or promote prescription medicines. Talk to your doctor or pharmacist about any medicine. In an emergency call 000. Read our editorial policy and Health Acknowledgement.