Mounjaro vs Ozempic: What Our Doctors Recommend for Weight Loss

Both Mounjaro (tirzepatide) and Ozempic (semaglutide) have transformed weight management, but they work differently and produce different results. Here is what the clinical evidence shows and how we approach prescribing at our practice.

Ozempic was the first of these medications to gain widespread attention. It is a GLP-1 receptor agonist, meaning it mimics the natural hormone GLP-1 that your body releases after eating. This hormone signals fullness to your brain, slows stomach emptying, and helps regulate blood sugar. Ozempic has been prescribed for type 2 diabetes since 2018, with weight loss recognised as a significant secondary benefit.

Mounjaro works through a different mechanism. It is a dual GIP and GLP-1 receptor agonist, activating two hormonal pathways simultaneously. This dual action appears to produce greater weight loss and metabolic improvement than GLP-1 alone.

The clinical data is now substantial. A landmark head-to-head trial published in The New England Journal of Medicine in May 2025 compared tirzepatide (Mounjaro) directly with semaglutide (Ozempic/Wegovy) in 751 non-diabetic adults over 72 weeks. The results were clear: Mounjaro users lost 20.2% of their body weight compared to 13.7% with semaglutide. Waist circumference dropped by 18.4 cm with Mounjaro compared to 13 cm with semaglutide.

Across the SURMOUNT clinical trials, Mounjaro consistently reduced both body weight and waist circumference regardless of how long someone had lived with obesity, with weight losses of approximately 21% at the highest dose over 72 weeks.

These numbers are averages. Individual results vary based on starting weight, metabolic profile, adherence to dosing schedules, dietary changes, and activity levels. Some of our patients see greater results; others see more modest improvements. The key is that both medications produce clinically meaningful weight loss when prescribed and monitored properly.

Side effects are similar for both medications. The most common are gastrointestinal: nausea, constipation, and diarrhoea. These typically occur during the initial dose titration period (the first few weeks at each new dose level) and settle as the body adjusts. At our practice, we manage this carefully by increasing doses gradually and providing practical dietary guidance to minimise discomfort.

The question patients ask most often is: which one should I choose? Our approach is individualised. We consider your medical history, current medications, previous weight loss attempts, blood sugar levels, and personal goals. For patients with type 2 diabetes or significant insulin resistance, the dual GIP/GLP-1 action of Mounjaro may offer particular advantages. For patients who prefer a weekly injection they can administer at home with minimal dose titration complexity, Ozempic may be the more straightforward starting point.

Cost is also a practical consideration. Both medications are prescribed privately for weight management in the UK, and prices vary. We are transparent about costs during your consultation so you can make an informed decision.

What we emphasise to every patient is that medication is one part of the picture. Regular consultations, blood tests to monitor metabolic health, and lifestyle changes (dietary improvements, increased physical activity, better sleep) all contribute to lasting results. Studies consistently show that patients who stop medication without establishing healthy habits tend to regain weight. Those who build sustainable routines during treatment maintain their progress far more effectively.

If you are considering Mounjaro or Ozempic for weight management, we welcome you to book a consultation at our Knightsbridge practice. Our experienced GPs will assess your situation, discuss the options candidly, and create a personalised plan. Call 020 7589 8965 or book online.