GLP-1 medicines such as semaglutide (Ozempic, Wegovy) and tirzepatide (Mounjaro) are the most significant advance in medical weight loss in decades, producing average body-weight reductions of roughly 15 to 21% in clinical trials. This guide covers how they work, who qualifies, realistic results, side effects, cost, and how to start safely on a doctor-led programme, all under a registered South African doctor.
Every weight-loss programme at mobivIVe is led 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. These are prescription medicines, so a telephone or virtual consultation with the doctor is required for every GLP-1 order.
What is medical weight loss with GLP-1 therapy?
Medical weight loss with GLP-1 therapy uses doctor-prescribed medicines, semaglutide or tirzepatide, to reduce appetite, slow stomach emptying and improve how the body handles blood sugar. It is prescribed and supervised by a registered doctor after a consultation, and the weekly pen is delivered to your door anywhere in South Africa. Unlike crash diets, it works on the biology that drives weight gain: appetite hormones, insulin signalling, and the body’s tendency to defend a higher weight.
How do GLP-1 medicines cause weight loss?
GLP-1 medicines mimic a natural gut hormone released after eating. They act on the brain to reduce hunger, slow how quickly food leaves the stomach, and improve insulin sensitivity, so you feel satisfied on smaller portions with fewer cravings. The natural hormone lasts only a minute or two; these medicines are engineered to last about a week per injection. Many people also describe less “food noise”, the constant background preoccupation with food that makes weight management so hard.
What is semaglutide, and how does it work?
Semaglutide is a once-weekly injection that reduces appetite and slows gastric emptying. In the STEP clinical-trial programme (New England Journal of Medicine) it produced an average of about 15% body-weight loss over 68 weeks, compared with about 2.4% on placebo. It is the active ingredient in the branded products Ozempic and Wegovy. Dosing starts low (typically 0.25mg per week) and steps up every four weeks to keep side effects low. See our full semaglutide and Ozempic page for options and pricing.
What is tirzepatide, and how is it different?
Tirzepatide is a newer, dual-action medicine that works on two hunger-regulating hormone pathways at once (GLP-1 and GIP). In the SURMOUNT programme it produced up to about 21% average body-weight loss over 72 weeks. In the first head-to-head trial (SURMOUNT-5, 2025) tirzepatide averaged 20.2% weight loss versus 13.7% for semaglutide. It is the active ingredient in Mounjaro. Which one suits you depends on your health, goals and tolerance, which is what your doctor consultation determines. See our tirzepatide and Mounjaro page for detail.
How much weight can you expect to lose?
Clinical trials show semaglutide produces about 15% average total body-weight loss and tirzepatide up to about 21%. Individual results vary with starting weight, diet, activity and how consistently you follow the programme. Most people notice reduced appetite within 2 to 4 weeks. These are trial averages, not guarantees, and the medicines work best alongside good nutrition and activity, which the mobivIVe team supports you through.
How quickly will I see results?
Most people notice reduced appetite and smaller portions within the first 1 to 2 weeks. Visible weight loss typically begins between weeks 4 and 8, and the most significant body-composition change is usually apparent from 12 to 16 weeks. Doses step up every four weeks specifically to minimise side effects while the body adjusts.
Am I a suitable candidate?
You may be a good candidate if you want structured, medically-supervised weight loss and can self-inject a weekly pen. Clinically, GLP-1 therapy is generally considered from a BMI of 30, or 27 with a weight-related condition such as type 2 diabetes, hypertension, sleep apnoea or PCOS. It needs extra care or may be unsuitable if you have a history of medullary thyroid cancer or MEN2, pancreatitis, or are pregnant or breastfeeding. Because these are prescription medicines, a telephone or virtual consultation with the doctor is required for every order, and they cannot be dispensed on a questionnaire alone.
Can I use GLP-1 therapy if I have type 2 diabetes?
Yes. GLP-1 medicines were originally developed for type 2 diabetes and have a well-established safety record in that group. They improve blood-sugar control while supporting weight loss. If you already take diabetes medication, the doctor reviews it during your consultation to avoid low blood sugar.
What are the side effects?
The most common side effects are digestive: nausea, constipation or mild diarrhoea. These are usually mild, worst in the first few weeks of a new dose, and settle as the body adapts. Gradual dose titration reduces their severity. Serious side effects are uncommon at correct doses, and hair loss and cardiovascular risk are not associated with correctly-dosed GLP-1 therapy. Your doctor talks you through what to expect and what to watch for.
What happens when I stop?
Some weight regain is common after stopping if lifestyle habits are not maintained, because appetite returns. Trial data found people who stopped abruptly regained a large share of lost weight within a year without sustained changes. This is why the mobivIVe programme includes maintenance guidance, and why many people step down to a lower maintenance dose rather than stopping suddenly.
How much does it cost in South Africa?
At mobivIVe, doctor-led, SAHPRA-registered semaglutide (Semagard) programmes start from R1,999 per pen and tirzepatide (Mounjaro) from R4,999, delivered nationwide, with your prescription assessment and ongoing support included. Medical aids do not cover GLP-1 therapy for weight management (obesity is not a Prescribed Minimum Benefit); cover applies to diagnosed type 2 diabetes only, so weight-management treatment is private pay. Full pricing is on the semaglutide and tirzepatide pages.
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
Check if a programme could suit you
Body mass index is one of the things a doctor looks at when deciding whether a weight management programme is appropriate. Work yours out below. It takes a few seconds and nothing is stored.
BMI is a rough screening measure only. It does not account for muscle mass, body composition or medical history, and it is not a diagnosis. Whether any treatment is appropriate for you is decided by a registered doctor at your consultation.
Compare your options: Semaglutide vs Tirzepatide · Ozempic vs Wegovy vs Mounjaro
How to start, in 3 simple steps
- Message us on WhatsApp. Tell our doctor-led team your goal. No clinic visit needed.
- Medical questionnaire & doctor consultation. Complete a short questionnaire, then a telephone or virtual consultation with the doctor, which is required for all GLP-1 medicines. If it is safe and suitable, a script is issued.
- Delivered to your door. Your prefilled pen is couriered anywhere in South Africa, and you begin your weekly routine with ongoing support.
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 July 2026. Not intended to diagnose, treat, cure or prevent any disease; individual results vary. Consult your healthcare provider.