Mounjaro vs Ozempic: Which GLP-1 Is Right for You?

If you've been researching GLP-1 weight loss medication in South Africa, you've almost certainly come across two names: Ozempic (semaglutide) and Mounjaro (tirzepatide). Both are injectable medications prescribed for weight management. Both are available in South Africa. But they work differently, produce different results, and come at different price points.

This guide breaks down everything you need to know so you — and your doctor — can make an informed decision together.

The Core Difference: How Each Medication Works

Both medications belong to the GLP-1 receptor agonist class — they mimic a gut hormone that suppresses appetite and slows digestion. But their mechanisms differ in an important way:

• Ozempic (semaglutide) is a GLP-1 receptor agonist — it activates one receptor pathway.
• Mounjaro (tirzepatide) is a dual GIP/GLP-1 receptor agonist — it activates two receptor pathways simultaneously. GIP (glucose-dependent insulinotropic polypeptide) works alongside GLP-1 to further reduce appetite and improve metabolic function.

This dual mechanism is why Mounjaro consistently shows higher weight loss in clinical trials. It's essentially hitting two appetite-regulating targets at once.

Head-to-Head Comparison

Weight Loss Results: What Do the Numbers Mean?

The landmark SURMOUNT trials showed that patients on Mounjaro lost an average of 20–22% of their body weight over 72 weeks. The STEP trials for Ozempic showed average weight loss of 12–15% over 68 weeks.

To put that in real terms: a 100 kg patient might lose approximately 20–22 kg on Mounjaro versus 12–15 kg on Ozempic, on average. These are averages — some people lose significantly more, some less. Individual response depends on adherence, diet, activity, metabolic factors, and genetics.

Important: both of these numbers represent substantial, clinically meaningful weight loss compared to lifestyle interventions alone (which typically achieve 3–5% sustained weight loss). Either medication is likely to produce results you'll notice.

Side Effect Profiles

The most common side effects for both medications are gastrointestinal — nausea, diarrhoea, and vomiting — and are most pronounced during the dose escalation phase in the first few months. They typically improve as your body adjusts.

Mounjaro side effects

• Nausea (most common)
• Diarrhoea
• Decreased appetite (intended effect)
• Vomiting
• Constipation
• Abdominal pain

Ozempic side effects

• Nausea (most common)
• Constipation (more so than Mounjaro)
• Vomiting
• Diarrhoea
• Abdominal pain
• Fatigue

The most serious (though rare) risk for both medications includes pancreatitis, gallbladder disease, and — based on animal studies — a theoretical thyroid tumour risk (though this has not been demonstrated in humans at therapeutic doses). Your doctor will review your full history before prescribing.

Cost Comparison in South Africa

Both medications are significantly more affordable in South Africa than in the United States or Europe, but remain a meaningful monthly expense that most medical aids do not cover for weight management.

Given that Mounjaro produces roughly 40–50% greater weight loss than Ozempic, many patients — and doctors — consider the additional cost worthwhile, particularly for those with significant weight to lose or weight-related health conditions.

Who Is Each Medication Best For?

Ultimately, this decision belongs to you and your doctor. The doctor will review your full medical history, current medications, comorbidities, and goals during your consultation before making a recommendation.