Mounjaro to Wegovy Switch

Wegovy and Mounjaro are part of a new generation of highly effective medicines for managing obesity. They work by targeting the body’s natural hormone pathways that influence appetite and eating behaviour. 

• Mounjaro contains tirzepatide, which acts on two hormone pathways, known as GIP and GLP-1.
• Wegovy contains semaglutide, which acts on the GLP-1 pathway alone. Wegovy is the UK equivalent of Ozempic, which is widely used in the United States for weight management. 

Although they act slightly differently, both treatments reduce appetite and regulate food-related behaviours. In practical terms, this means patients often feel full sooner, experience fewer cravings, and find it easier to make changes to their eating patterns to support their weight management goals. 

Both medicines have been shown to deliver significant weight loss alongside improvements in blood pressure, blood sugar control, cholesterol levels, and overall quality of life. 

Side effects are broadly similar. Both can cause nausea, diarrhoea, constipation, or indigestion, particularly when starting treatment. Wegovy is slightly more likely to lead to people stopping due to stomach-related side effects, whereas Mounjaro has been linked more often to injection site reactions.

Avg weight loss:

Wegovy - 17%
Mounjaro - 22.5%

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Many patients find Wegovy offers practical advantages, particularly when cost or personal preference makes continuing Mounjaro more difficult. While Mounjaro has been shown to deliver greater overall weight loss in clinical trials, Wegovy is still a highly effective treatment with its own set of benefits.  These include: 

• Ease of use – Wegovy pens come with needles already included and have a longer shelf life.
• Less chance of injection site reactions compared with Mounjaro.
• Weight loss results – In clinical trials, 1 in 3 patients lost at least 20% of their body weight, and on average patients lost 17% after nearly two years of treatment
• Health improvements – Alongside weight reduction, studies have shown improvements in blood pressure, blood sugar control, cholesterol levels, and quality of life.
• Compatibility with oral contraceptives – The manufacturer advises that Wegovy is not anticipated to decrease the effectiveness of oral contraceptives

After a careful review of the available evidence, at Cloud Pharmacy we offer the following guidance for patients who are considering switching: 

• If you are currently taking 2.5mg, 5mg or 7.5mg of Mounjaro, the usual starting dose is 0.5mg of Wegovy once weekly. 
• If you are taking 10mg of Mounjaro or above, the usual starting dose is 1.0mg of Wegovy once weekly. 
• Patients who wish to take a more cautious approach can start at 0.25mg of Wegovy regardless of their current Mounjaro dose.

It is very important that you wait seven days after your last Mounjaro injection before starting Wegovy. This helps your body adjust and reduces the risk of side effects. 

This guidance is general and may be adjusted to suit your individual needs after discussion with your prescriber. As with Mounjaro, your Wegovy dose will be increased gradually over time, depending on how you respond and how well you tolerate treatment. This gradual, step-by-step approach is designed to reduce side effects and support long-term success.

Most patients find they experience similar side effects on Wegovy to Mounjaro. It is most common to experience some side effects when first starting Wegovy, especially while your body is adjusting. The most frequently reported include:

• Nausea, vomiting, diarrhoea, or constipation
• Indigestion or reflux
• Fatigue or low energy
• Low blood sugar 

These effects usually ease over time and can be different for each patient. Some patients also notice that their appetite changes feel different compared with Mounjaro. Keeping in touch with your prescriber during this period is important, so that they can support you with managing symptoms and adjusting treatment if needed. 

It is especially important that you contact us promptly if you begin to experience any significant or worrying side effects while taking Mounjaro or Wegovy. Our team can provide guidance and ensure you receive the care you need without delay.