Mounjaro vs Wegovy: Comparing Two Leading Weight Loss Treatments

Weight loss medications have become an increasingly important part of modern weight management, with Mounjaro and Wegovy among the most well-known treatments currently available. In this blog, we’re exploring Mounjaro vs Wegovy: Comparing two leading weight loss treatments.

While these treatments are often grouped together as “GLP-1 medications”, they are not the same.

They are both once-weekly injections; however, Mounjaro and Wegovy work through different hormonal pathways and follow different approaches to increasing the dose during treatment. There are also some differences in clinical results and side effects. Explore weight loss injections online.

So, what’s the difference between Mounjaro and Wegovy, and how do they compare?

Mounjaro and Wegovy: What are they?

Mounjaro contains the active ingredient tirzepatide, while Wegovy contains semaglutide.

Both are given as a once-a-week injection and are used alongside a reduced-calorie diet and increased physical activity as part of a weight management programme for eligible patients. While both medicines can reduce appetite and help people feel fuller, they achieve this in slightly different ways.

The key difference lies in the receptors they target.

Wegovy

Wegovy contains semaglutide, which activates the GLP-1 receptor.

GLP-1 (glucagon-like peptide-1) is a hormone naturally released by the gut after we eat. It helps regulate appetite, digestion and blood glucose levels.

When the GLP-1 receptor is activated, several things happen within the body. It can increase insulin secretion when blood glucose levels are elevated, reduce glucagon secretion, slow the movement of food through the stomach and increase feelings of fullness.

GLP-1 also acts on areas of the brain involved in appetite regulation. This can help reduce hunger and food intake.

Semaglutide is designed to mimic the effects of naturally occurring GLP-1 but to remain active in the body for much longer, allowing it to be administered once a week.

This is the main pathway targeted by Wegovy. Buy Wegovy injections online.

Mounjaro

Tirzepatide activates both the GLP-1 and GIP receptors. This means it is known as a dual GIP/GLP-1 receptor agonist.

GIP (glucose-dependent insulinotropic polypeptide) is another hormone the body naturally releases after eating. Like GLP-1, it plays a role in the body’s response to food and helps stimulate insulin secretion in a glucose-dependent manner.

GIP signalling is also involved in energy and nutrient metabolism, with GIP receptors found in tissues including the pancreas, brain and adipose tissue.

By activating both GIP and GLP-1 receptors, tirzepatide acts on two interconnected hormonal pathways involved in appetite, glucose regulation and metabolism.

• Wegovy → GLP-1
• Mounjaro → GLP-1 + GIP

How much weight loss can you expect?

Both Mounjaro and Wegovy have demonstrated significant weight loss in clinical trials.

However, we now have particularly useful evidence because the two medicines have been directly compared in the same clinical trial. Read about medical weight loss treatments.

What did the SURMOUNT-5 trial find?

The SURMOUNT-5 trial compared tirzepatide with semaglutide in 751 adults living with obesity, or who are overweight with at least one weight-related health condition. Participants were randomised to receive tirzepatide or semaglutide once weekly, along with advice on a reduced-calorie diet and increased physical activity.

After 72 weeks of treatment, the average weight loss was:

• Tirzepatide (Mounjaro): 20.2%
• Semaglutide (Wegovy): 13.7%

This means that, on average, participants taking tirzepatide lost a greater percentage of their starting body weight than those taking semaglutide.

There was also a greater reduction in waist circumference with tirzepatide, with an average reduction of 18.4 cm compared with 13.0 cm with semaglutide.

It is important to remember that these are average results from a clinical trial, not a prediction of what an individual patient will lose. Weight loss can vary considerably between individuals.

The SURMOUNT-5 results are particularly useful because they directly compare the two medicines.

What about the side effects of weight-loss medications?

Mounjaro and Wegovy have similar side-effect profiles, with gastrointestinal symptoms being among the most commonly reported.

These can include:

• Nausea
• Diarrhoea
• Constipation
• Vomiting
• Abdominal discomfort
• Reduced appetite

These side effects are particularly common when starting treatment or increasing the dose.

Gastrointestinal symptoms are temporary and improve as the body becomes accustomed to the medication. This is one of the reasons both treatments use a gradual dose escalation schedule rather than starting immediately at the highest dose.

More serious side effects can occur less commonly, so it is important that treatment is prescribed and monitored appropriately and that patients understand when they should seek medical advice.

How do the doses compare?

Although both medicines are taken once a week, their dosing schedules are different.

Mounjaro is generally started at a low dose and gradually increased. The UK prescribing information recommends starting at 2.5 mg once weekly, then increasing to 5 mg after four weeks. Further increases can then be made in 2.5 mg increments, with at least four weeks spent on the current dose.

Wegovy also follows a gradual escalation schedule. Treatment starts at 0.25 mg once weekly, then increases over several weeks toward the maintenance dose.

The purpose of gradual dose escalation is not simply to reach the highest dose as quickly as possible. It allows the body time to adjust to the medication and can help improve tolerability, particularly when it comes to gastrointestinal side effects.

The appropriate dose can therefore depend on the individual, their response to treatment and how well they tolerate each stage of the dose escalation process.

The bottom line

Mounjaro and Wegovy are two leading treatments in the rapidly developing field of weight management, but they are not identical medications.

Wegovy works through the GLP-1 pathway, while Mounjaro activates both GLP-1 and GIP receptors. Both have demonstrated significant weight loss in clinical trials, with tirzepatide producing greater average weight loss than semaglutide in the direct SURMOUNT-5 comparison.

If you’d like more information about weight loss treatments or to find out whether you’re eligible, complete our consultation form. One of our UK-registered pharmacists will review your information thoroughly. Our customers receive full support throughout the entire journey. Read about weight loss pills and oral treatments.

References

• Mounjaro (tirzepatide) – Summary of Product Characteristics. Eli Lilly and Company Limited. Electronic Medicines Compendium (eMC).

• Wegovy (semaglutide) – Summary of Product Characteristics. Novo Nordisk Limited. Electronic Medicines Compendium (eMC).

• Tirzepatide as Compared with Semaglutide for the Treatment of Obesity https://www.nejm.org/doi/full/10.1056/NEJMoa2416394