GLP-1 Medications Compared: Ozempic vs Wegovy vs Mounjaro

Why This Comparison Matters

GLP-1 medications have transformed obesity medicine. For the first time, we have prescription drugs that can achieve 15–22% weight loss — results that were previously only seen with bariatric surgery. But with multiple options now available in Australia, patients frequently ask: *which one is right for me?*

The honest answer is: it depends. This article explains how each medication works, what the evidence shows, and how Dr Chong approaches the decision in clinical practice.

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What Is a GLP-1 Receptor Agonist?

GLP-1 (glucagon-like peptide-1) is a hormone naturally released from the gut after eating. It:

• Signals the pancreas to release insulin in response to glucose
• Reduces glucagon secretion (which lowers blood sugar)
• Slows stomach emptying (you feel full longer)
• Acts on appetite centres in the brain to reduce hunger

GLP-1 receptor agonists mimic this hormone at much higher, sustained levels than the body naturally produces — resulting in significantly reduced appetite, slower digestion, and meaningful weight loss.

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Ozempic (Semaglutide 0.5mg / 1mg)

Active ingredient: Semaglutide

Approved indication in Australia: Type 2 diabetes management

PBS-listed: Yes (for T2DM only)

Dosing: Weekly subcutaneous injection

Starting dose: 0.25mg → titrate up to 0.5mg or 1mg

How It Works

Ozempic is a GLP-1 receptor agonist. It primarily reduces appetite and slows gastric emptying, resulting in lower caloric intake and improved blood glucose control in type 2 diabetes.

Efficacy for Weight Loss

In the SUSTAIN clinical trials, patients on semaglutide 1mg lost an average of 6–7% of body weight over 52 weeks. This is meaningful, but lower than the weight management-specific formulations because the dose is lower.

Key Points

• The most widely prescribed of the three in Australia
• PBS-subsidised for type 2 diabetes (low cost for eligible patients)
• Not approved or PBS-listed for weight management alone
• Same active ingredient as Wegovy but at a lower dose
• Well-tolerated; side effects well-characterised over many years of use

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Wegovy (Semaglutide 2.4mg)

Active ingredient: Semaglutide (same as Ozempic, higher dose)

Approved indication in Australia: Chronic weight management

PBS-listed: No — private prescription only

Dosing: Weekly subcutaneous injection

Starting dose: 0.25mg → titrate over 16–20 weeks to 2.4mg

Approximate cost: $260–$380/month

How It Works

Wegovy uses the same semaglutide molecule as Ozempic but at a significantly higher maintenance dose (2.4mg vs 1mg). The higher dose produces stronger appetite suppression via central (brain) mechanisms beyond just the gut effect.

Efficacy for Weight Loss

In the landmark STEP 1 trial, patients on semaglutide 2.4mg lost an average of 14.9% of body weight over 68 weeks — with one-third of participants losing more than 20%. This level of weight loss has significant benefits for metabolic health, blood pressure, cardiovascular risk, and joint symptoms.

Key Points

• The weight management-specific formulation of semaglutide
• Requires slow titration to minimise nausea
• More effective than Ozempic for weight loss due to higher dose
• More expensive (private prescription, ~$260–$380/month)
• Not suitable for patients with personal or family history of medullary thyroid carcinoma or MEN2 syndrome

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Mounjaro (Tirzepatide)

Active ingredient: Tirzepatide

Approved indication in Australia: Type 2 diabetes (weight management TGA review ongoing as of 2026)

PBS-listed: No for weight management — private prescription only

Dosing: Weekly subcutaneous injection

Starting dose: 2.5mg → titrate up to 5mg, 10mg, or 15mg

Approximate cost: $300–$700/month depending on dose

How It Works

Tirzepatide is a dual GIP/GLP-1 receptor agonist — it activates both the GLP-1 receptor (like semaglutide) *and* the GIP (glucose-dependent insulinotropic polypeptide) receptor. GIP is another gut hormone involved in insulin secretion and fat storage.

This dual mechanism appears to produce stronger metabolic effects than GLP-1 alone, including greater appetite suppression, enhanced insulin sensitivity, and improved lipid profiles.

Efficacy for Weight Loss

In the SURMOUNT-1 trial — the largest weight management trial conducted to date — patients on tirzepatide 15mg lost an average of 20.9% of body weight over 72 weeks. More than half of participants lost at least 20% of their body weight. These are results that approach what is seen with some bariatric surgical procedures.

Key Points

• More effective than semaglutide in head-to-head analyses
• Better tolerated in some patients (lower rates of nausea at equivalent doses)
• Higher monthly cost at maximum doses
• Not yet PBS-listed for weight management in Australia
• Also improves blood pressure, triglycerides, and cardiovascular risk markers

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Head-to-Head: Key Differences at a Glance

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Side Effects: What to Know

All three medications share similar side effect profiles, because they all slow gastric emptying and act on gut receptors:

Common (especially early in treatment):

• Nausea (most frequent — typically improves after first 4–8 weeks)
• Vomiting
• Diarrhoea or constipation
• Reduced appetite (expected and intended)
• Fatigue

Less common:

• Heartburn or reflux
• Injection site reactions

Rare but important:

• Pancreatitis (seek medical attention for severe abdominal pain)
• Gallstones (rapid weight loss increases gallstone risk with any treatment)
• Hypoglycaemia (mainly a risk in patients also on insulin or sulfonylureas)

Contraindications:

• Personal or family history of medullary thyroid carcinoma
• Multiple endocrine neoplasia syndrome type 2 (MEN2)
• Pregnancy or breastfeeding
• Severe gastrointestinal disease

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Which One Does Dr Chong Prescribe?

There is no single "best" medication — the right choice depends on:

1. Your diagnosis — if you have type 2 diabetes, Ozempic may be PBS-eligible, dramatically reducing cost
2. Your budget — Wegovy and Mounjaro are private-prescription only; cost matters
3. Your weight loss goals — patients needing >15% weight loss may benefit most from Mounjaro
4. Your medical history — contraindications, other medications, previous GLP-1 experience
5. Tolerability — some patients do better on one agent than another

Dr Chong's approach is to make a recommendation based on your individual situation, explain the evidence honestly, and discuss costs upfront before prescribing.

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Important: Compounded and Imported Semaglutide

Following global shortages of Ozempic and Wegovy, a market emerged for compounded semaglutide from compounding pharmacies. While this was a regulatory option during the shortage period, Dr Chong does not prescribe compounded or imported GLP-1 medications.

TGA-approved formulations from Novo Nordisk and Eli Lilly have been manufactured to strict pharmaceutical standards, tested in large-scale clinical trials, and have known pharmacokinetic profiles. Compounded products vary in purity, concentration, and stability.

Dr Chong prescribes only TGA-approved medications.

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Book a Consultation

If you're considering GLP-1 pharmacotherapy for weight management in Bayswater or Melbourne's eastern suburbs, Dr Chong can assess whether these medications are appropriate for you and advise on the best option for your specific situation.

Call (03) 9967 1996 or book online via HotDoc. No referral required at Medi Weight Loss, Bayswater.