Mounjaro vs Wegovy: what’s the difference?

Wegovy contains semaglutide, a GLP-1 receptor agonist that mimics the effect of the body’s natural GLP-1 hormone. This hormone helps regulate appetite, feelings of fullness, and blood sugar levels.

Mounjaro contains tirzepatide, a so-called dual agonist that activates both GLP-1 and GIP receptors. The combination of these two hormonal pathways influences appetite, fullness and energy balance through partly overlapping mechanisms.

In clinical studies, tirzepatide has shown slightly greater average weight loss compared with semaglutide when used to treat obesity. However, both medicines have shown significant effects and are considered effective medical treatments for obesity. Semaglutide and tirzepatide are also used in the treatment of type 2 diabetes.

The choice between treatments is based on an individual medical assessment, treatment goals, tolerance and availability.

How do the medicines support weight loss?

Both Wegovy (semaglutide) and Mounjaro (tirzepatide) are prescription medicines taken as a self-administered subcutaneous injection once a week. They affect the body’s appetite regulation and energy balance through hormonal pathways involved in hunger, fullness and blood sugar control.

Wegovy (semaglutide)

Semaglutide is a GLP-1 receptor agonist. This means it activates the same receptor as the body’s natural GLP-1 hormone, which is released after eating. GLP-1 contributes to:

• Increased feelings of fullness
• Reduced hunger
• Slower stomach emptying
• Improved glucose regulation

Together, these effects often make it easier to maintain a lower energy intake.

Mounjaro (tirzepatide)

Tirzepatide is a dual agonist that activates both GLP-1 and GIP receptors. The effects of these hormones influence appetite regulation and blood sugar balance. Clinical studies show that tirzepatide can lead to reduced energy intake and significant weight loss in many people.

Indication

Both Wegovy and Mounjaro are approved for weight management in adults with:

• BMI ≥30 kg/m² (obesity), or
• BMI ≥27 kg/m² with at least one weight-related health condition such as high blood pressure, dyslipidaemia, or obstructive sleep apnoea.

Treatment should be used alongside dietary changes and increased physical activity.

Comparison of effects and results

A common question is which treatment leads to greater weight loss. Both semaglutide (Wegovy) and tirzepatide (Mounjaro) have been studied in large research programmes and have shown meaningful effects in the treatment of obesity.

In the STEP programme, where semaglutide 2.4 mg was studied for obesity, the average weight loss was around 15% after 68 weeks of treatment combined with lifestyle support.

In the SURMOUNT programme, tirzepatide showed average weight loss of up to around 20% after 72 weeks, depending on the dose.

In a head-to-head study comparing tirzepatide and semaglutide in obesity treatment, participants treated with tirzepatide achieved greater average weight loss than those treated with semaglutide. However, both medicines demonstrated clinically meaningful effects.

Beyond weight reduction, both semaglutide and tirzepatide have shown favourable effects on cardiometabolic risk factors such as blood pressure, waist circumference and glucose regulation. In cardiovascular outcome studies, semaglutide has also been shown to reduce the risk of major cardiovascular events in people living with overweight or obesity who already have established cardiovascular disease.

It’s important to remember that these figures represent average results. Individual responses vary, and the choice of treatment is based on a medical assessment, tolerance, treatment goals and personal circumstances.

Differences and similarities

In clinical practice, the use of Mounjaro (tirzepatide) and Wegovy (semaglutide) is similar in many ways. However, there are some differences in terms of approved indications, active substance and dosing.

• Active substance
Wegovy contains semaglutide as the active ingredient (the same substance used in Ozempic), while Mounjaro contains tirzepatide.

• Approval
Wegovy is specifically approved for weight management alongside lifestyle changes.

Mounjaro is approved for the treatment of type 2 diabetes in adults with insufficient glycaemic control, in addition to diet and exercise. It is also approved for weight management alongside a calorie-reduced diet and increased physical activity in adults with obesity or overweight with at least one weight-related health condition.

• Administration
Both medicines are given as an injection into the fatty tissue under the skin (usually the abdomen or thigh) once a week. Always read the patient information leaflet before use to ensure correct handling and dosing.

Mounjaro is supplied as a solution in a pre-filled injection pen and is available in doses of 2.5 mg, 5 mg, 7.5 mg, 10 mg, 12.5 mg and 15 mg. The starting dose is 2.5 mg once a week and may be increased if needed after 4 weeks.

Wegovy is supplied as a solution in a pre-filled injection pen and is available in doses of 0.25 mg, 0.5 mg, 1 mg, 1.7 mg and 2.4 mg. The starting dose is 0.25 mg once a week and can be increased gradually if needed.

Side effects

Because both medicines affect the digestive system, their side effect profiles are broadly similar. The most common side effects for both treatments include nausea, diarrhoea, constipation and heartburn or acid reflux. Gastrointestinal side effects are most common during the early phase of treatment or when the dose is increased, and they often improve over time.

Acute pancreatitis has been observed in patients treated with both Mounjaro and Wegovy, and treatment should be stopped if this is suspected. Gallbladder-related events, such as gallstones, have also been reported and may be associated with rapid weight loss.

It is also important to be aware of the risk of dehydration caused by gastrointestinal symptoms such as nausea, vomiting and diarrhoea. The safety profile of both medicines is well documented, but people receiving treatment should be followed up regularly as part of medical obesity care.

Overall, the pattern of side effects is similar for tirzepatide and semaglutide, with gastrointestinal symptoms being the most common. However, intensity and tolerance vary between individuals and may be influenced by the dose level and the speed of dose escalation.

Gradual dose increases using the principle of the lowest effective dose are important to improve tolerance and reduce the risk of side effects, regardless of which medicine is used.

Interactions with other medicines

When someone is treated with Mounjaro (tirzepatide) or Wegovy (semaglutide), it’s important to be aware that the treatment may affect, or be affected by, other medicines taken at the same time. Both tirzepatide and semaglutide slow stomach emptying, which can change how quickly or how much of other medicines are absorbed by the body. This mainly affects medicines taken orally, where the effect may be delayed or, in some cases, reduced.

If you use medicines like these, you should inform your doctor before starting treatment with tirzepatide or semaglutide.

Extra caution is also needed when these medicines are used together with sulfonylureas or insulin, as the risk of hypoglycaemia may increase when they are combined with Mounjaro or Wegovy.

To reduce the risk of side effects and help ensure treatment works as intended, always inform your doctor about all medicines you take, including over-the-counter medicines and herbal products. Your doctor may adjust the dose or treatment if needed.

How Yazen works with medical treatment

The choice between Mounjaro and Wegovy is always based on an individual medical assessment. Factors considered include BMI, the presence of related health conditions, previous treatment response, tolerance and personal preferences.

Treatment decisions are made together with a doctor and tailored to each person’s medical situation and treatment goals. The aim is to choose the treatment that offers the best balance between effectiveness, safety and long-term sustainability.

Whichever medicine is used, treatment is combined with structured lifestyle support, including nutrition guidance, support around physical activity and regular follow-up. This is a central part of achieving and maintaining results over time.

Sources

EMA – Wegovy (semaglutide) Medicine Information
https://www.ema.europa.eu/en/medicines/human/EPAR/wegovy

EMA – Mounjaro (tirzepatide) Medicine Information
https://www.ema.europa.eu/en/medicines/human/EPAR/mounjaro

The New England Journal of Medicine – Tirzepatide Once Weekly for the Treatment of Obesity
https://www.nejm.org/doi/full/10.1056/NEJMoa2206038

The New England Journal of Medicine – Once-Weekly Semaglutide in Adults with Overweight or Obesity
https://www.nejm.org/doi/full/10.1056/NEJMoa2032183

The New England Journal of Medicine – Semaglutide and Cardiovascular Outcomes in Obesity without Diabetes
https://www.nejm.org/doi/full/10.1056/NEJMoa2307563

The New England Journal of Medicine – Tirzepatide as Compared with Semaglutide for the Treatment of Obesity
https://www.nejm.org/doi/full/10.1056/NEJMoa2416394

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