The quick answer
Both are once-weekly injections. Mounjaro (tirzepatide) produces more average weight loss — up to ~21% in trials versus ~15% for semaglutide — and beat semaglutide head-to-head. Ozempic (semaglutide) is cheaper per month and longer established. Neither is “best” for everyone: it depends on your goals, budget, tolerance and what's in stock.
Ozempic vs Mounjaro: side by side
| Feature | Ozempic | Mounjaro |
|---|---|---|
| Active ingredient | Semaglutide (GLP-1) | Tirzepatide (GIP + GLP-1) |
| How often | Once weekly | Once weekly |
| Avg. weight loss (trials) | ~15% (STEP, at 2.4 mg) | ~21–22.5% (SURMOUNT-1, top dose) |
| SA registration | Type 2 diabetes (weight loss off-label) | Diabetes + weight management (late 2025) |
| Typical price / month | R2 700 – R3 300 | R3 500 – R4 600 |
| Form | Multi-dose pen | Single-dose pens / vials |
| Common side effects | Nausea, constipation, diarrhoea | Nausea, constipation, diarrhoea |
| Head-to-head | Lost ~13.7% in SURMOUNT-5 | Won SURMOUNT-5 (~20.2%) |
Which might suit you
Lean Mounjaro if maximum weight loss is the priority and the higher cost is manageable. Lean Ozempic if budget matters more, if it's what's reliably available, or if you tolerate it well at a lower dose. If on-label weight-loss use matters to you, note that Wegovy (the weight-management semaglutide) is the registered semaglutide option — see Wegovy vs Mounjaro.
This is general information, not a recommendation for your situation. The right choice depends on your health, budget, what's in stock and a clinician's judgement. Get a personalised assessment from a registered provider
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