Wegovy vs Ozempic vs Mounjaro: Understanding the key differences

Wegovy, Ozempic and Mounjaro are breakthrough treatments for diabetes and obesity, boosting satiety hormones, reducing appetite and slowing digestion, so you eat less and stay full longer.

Discover which option suits you.

Active ingredients and mechanisms

Wegovy and Ozempic both contain semaglutide, a GLP-1 receptor agonist that increases insulin levels in your body and decreases your blood sugar (glucose). “Semaglutide helps slow gastric emptying – when the stomach gradually moves food and liquids into the small intestine,” says Dr Marius Wasserfall, a specialist physician at Mediclinic Panorama. “It also primarily stimulates glucose-dependent insulin secretion and reduces glucagon (a hormone that prevents blood sugar from dropping too low, especially during hunger or exercise). This leads to both glycaemic (blood sugar) control and weight loss.”

Mounjaro contains tirzepatide, a drug that works in two ways to help control blood sugar and appetite. “Unlike semaglutide, tirzepatide targets both GLP-1 and GIP receptors,” says Dr Wasserfall. “This dual action improves metabolic control and may be slightly more effective for managing diabetes and supporting weight loss than single-target drugs like Wegovy and Ozempic.”

Primary approved uses

The main difference between these medicines is how they’re used. As Dr Wasserfall explains, Ozempic (low-dose semaglutide) is approved to treat type 2 diabetes and reduce major heart risks in diabetic patients. “Weight loss is often a side benefit, but using Ozempic for weight management in non-diabetic patients is off label, which affects medical aid cover,” he says.

Wegovy (high dose semaglutide) was specifically created and approved for chronic weight management in adults with a BMI of 30 or higher, or those with a BMI of 27 or higher who have at least one weight-related health condition. Wegovy is registered for chronic weight management, not specifically for glycaemic control in type 2 diabetes, despite containing the same ingredient as Ozempic (semglalutide) at a higher dose,” says Dr Wasserfall. “Patients who need formal diabetes management typically receive Ozempic instead.”

Tirzepatide offers the most versatile approach, with dual approval pathways. In South Africa, we have the various doses available under the name Mounjaro, while in other countries it is marketed under the name Zepbound. “In addition to treating diabetes, Mounjaro is now also registered for weight management,” says Dr Wasserfall.

 “This dual approval makes it especially useful for patients with both diabetes and serious weight issues, delivering broader metabolic benefits in a single treatment,” he adds. 

Dosing strategies

Ozempic usually starts at 0.25mg once a week for a month, increases to 0.5mg weekly for the next month, and then to 1mg weekly if the body tolerates it. “The reason for starting low is purely to limit the gastrointestinal side effects,” says Dr Wasserfall. “Start low, go slow, aim high.” The maximum dose of Ozempic is 1mg weekly.

 Wegovy starts with the same approach to limit gastrointestinal side-effects, starting at 0.25mg weekly for one month, then 0.5mg weekly for one month before reaching the 1mg weekly dose. “It can then go up to 1.7mg weekly for four weeks, and, if the patient can tolerate it, up to the current maximum dose of 2.4mg weekly. “Ongoing trials are evaluating much higher doses to determine the additional weight-loss effects,” says Dr Wasserfall.  

Mounjaro uses a different approach to dosing. It starts at 2.5mg once a week and can be increased to a maximum of 15mg a week. “The mechanism of action is slightly different from Ozempic and Wegovy and the comparative trials show better weight loss and diabetes control compared to 1mg semaglutide (Ozempic),” says Dr Wasserfall. “However, the 2.4mg semaglutide (Wegovy) compared very favourably to tirzepatide (Mounjaro).”

Efficacy and clinical outcomes

For weight loss, high-dose tirzepatide – Mounjaro or Zepbound 15mg – has shown slightly better results.

“Trials show an average weight loss of 14-16% with semaglutide, with one in three people losing more than 20% of their body weight, compared with 21-23% for tirzepatide, where one in three loses more than 25%,” says Dr Wasserfall.

He adds that in diabetes management, trials show Mounjaro achieves slightly greater reductions in HbA1c than Ozempic, although Ozempic is supported by more completed trials demonstrating organ-protective benefits, including cardiovascular and kidney protection.

 “Ozempic offers excellent diabetes control with proven cardiovascular benefits, making it particularly valuable for diabetic patients with heart disease risk factors. Wegovy , however, isn’t licensed for diabetes treatment but has been shown to improve blood pressure and other cardiometabolic risk factors.”

Cost considerations

At the time of publication, the cost of these medications varied widely. When considering treatment, the potential benefits should outweigh the cost, and patients should discuss available options with their doctor. These medications must be prescribed by a medical practitioner, who can provide appropriate counselling and ensure they’re used responsibly and for approved indications.

Dr Wasserfall adds that the FDA and SAHPRA have warned the public against buying compounded or counterfeit versions of semaglutide and tirzepatide, citing evidence of serious harm, including hospitalisation and death. “These products are neither registered nor regulated, and the authorities strongly advise against their use,” he cautions.

Key conclusions

“Ozempic is the best choice if your main goal is diabetes management and organ protection, particularly for if you have cardiovascular risk factors or kidney disease,” says Dr Wasserfall.

“For patients who meet the clinical criteria for weight management – namely a BMI over 30, or a BMI over 27 with at least one related health condition – Wegovy is more effective than Ozempic when weight loss is the main objective.

“Mounjaro offers the greatest weight-loss effect at higher doses, while also providing effective blood-sugar control at lower doses, and should be prescribed and used within approved clinical guidelines.”

Dr Wasserfall adds that you can’t use these drugs for a few months and then expect to stop and keep the weight off. “Trials have confirmed if you stop the Ozempic/Wegovy/Mounjaro you will regain more than 80% of the weight you lost in less than two years,” he says. “You need to see these drugs as a long-term treatment strategy.”