Semaglutide and tirzepatide are the two leading prescription weight-loss injections in South Africa. Both are weekly injections that reduce appetite and drive meaningful weight loss, but they work differently and one is generally more powerful. This guide compares them fairly so you can decide, with your doctor, which suits you.
Reviewed by Dr Chris van Zyl (registered as M.C. van Zyl, HPCSA MP0287067), who is licensed to both prescribe and dispense medicines under a Section 22C dispensing licence. Both medicines are prescription treatments, dispensed only after a required telephone or virtual consultation with our registered doctor.
| Feature | Semaglutide | Tirzepatide |
|---|---|---|
| Brand names | Ozempic, Wegovy | Mounjaro, Zepbound |
| How it works | GLP-1 receptor agonist | Dual GIP + GLP-1 agonist |
| Average weight loss | ~15% of body weight | ~20 to 22% of body weight |
| Head-to-head | Effective, established | Superior in direct trial |
| Dosing | Weekly injection | Weekly injection |
| Side effects | Mainly mild nausea and GI, usually settle | Similar, mainly GI |
| Best for | A proven, well-established option | Maximum weight loss |
| Prescription | Yes, doctor-led | Yes, doctor-led |
What is the difference between semaglutide and tirzepatide?
Both reduce appetite and food intake, but tirzepatide acts on two gut hormone pathways (GIP and GLP-1) while semaglutide acts on one (GLP-1). That extra mechanism is why tirzepatide tends to produce more weight loss for many people. See our semaglutide page and tirzepatide page for each on its own.
Which causes more weight loss?
On average, tirzepatide. In the STEP trial semaglutide produced around 15% body-weight loss, while SURMOUNT-1 showed tirzepatide reaching roughly 20 to 22%. In the SURMOUNT-5 head-to-head trial comparing the two directly, tirzepatide produced significantly more weight loss than semaglutide. Individual results still vary with dose, diet and consistency.
How do they work differently?
Semaglutide mimics GLP-1, a hormone that curbs appetite and slows stomach emptying. Tirzepatide mimics GLP-1 as well as GIP, a second hormone involved in how the body handles food and energy. Acting on both pathways gives tirzepatide a stronger effect on appetite and metabolism for many people.
Which has more side effects?
The side-effect profiles are similar: mostly mild to moderate nausea and other gut symptoms that usually settle as your body adjusts, especially when the dose is increased gradually. Because tirzepatide is more powerful, some people notice slightly stronger appetite suppression. Your doctor titrates the dose to keep you comfortable.
Which one is right for me?
If your priority is the greatest possible weight loss and you tolerate it well, tirzepatide is often the stronger choice. If you prefer a longer-established option, semaglutide is highly effective and widely used. The right pick depends on your health history, goals and budget, which is exactly what the doctor review covers. Our medical weight-loss guide explains the full programme.
How do I start either one in South Africa?
Both are prescription treatments, so it starts with a required telephone or virtual consultation with our registered doctor, who assesses your suitability. Once a script is issued, your prefilled pen is couriered anywhere in South Africa with clear dosing instructions.
Comparing prices? See what every weight loss injection costs in South Africa in 2026, including Ozempic, Wegovy and Mounjaro.
Looking for a specific brand? Ozempic in South Africa · Wegovy in South Africa · Mounjaro in South Africa
How to start, in 3 simple steps
- Message us on WhatsApp. Tell our doctor-led team your goal.
- Doctor consultation. You have a telephone or virtual consultation with our registered doctor, who assesses your suitability and issues a script if the treatment is right for you.
- Delivered to your door. Your prefilled pen is couriered anywhere in South Africa, with clear dosing instructions.
Medically reviewed by Dr Chris van Zyl This guide was written and reviewed by mobivIVe’s medical team, led by Dr Chris van Zyl, an HPCSA-registered medical doctor (registered as M.C. van Zyl, HPCSA reg. no. MP0287067) who is licensed to both prescribe and dispense medicines under a Section 22C dispensing licence. Last reviewed August 2026. Not intended to diagnose, treat, cure or prevent any disease; individual results vary. Consult your healthcare provider.