Switching from Mounjaro to Wegovy: Key Insights for UK Patients

Considering the Differences Between Mounjaro® and Wegovy®

At Haus of Ästhetik, we recognise that many people are seeking clarity around the differences between Mounjaro® (tirzepatide) and Wegovy® (semaglutide). Recent changes in pricing, NHS commissioning decisions, and medicine supply have all contributed to increased discussion across the UK about whether one treatment may be chosen over the other.

This blog is provided for information and awareness only. If you are considering starting, stopping, or switching between prescription weight‑management medicines, this must be done in consultation with a qualified prescriber or your GP.

1. How do Mounjaro® and Wegovy® differ?

Wegovy® (semaglutide) is a GLP‑1 receptor agonist. It works by mimicking the naturally occurring GLP‑1 hormone, slowing gastric emptying, reducing appetite, and improving blood‑glucose regulation.

Mounjaro® (tirzepatide) is a dual‑action medicine that targets both GLP‑1 and GIP receptors. By acting on two metabolic pathways rather than one, clinical trials have shown greater average weight loss in some populations compared with semaglutide.

In simple terms, Wegovy® works through a single hormonal pathway, while Mounjaro® works through two. Both are prescription‑only medicines, and both have demonstrated effectiveness in high‑quality clinical studies.

2. UK regulatory and commissioning context

In the UK, it is important to distinguish between licensing and NHS availability. Both Wegovy® and Mounjaro® are licensed medicines, meaning they have been assessed for safety and efficacy. However, licensing does not automatically equate to NHS funding.

Wegovy® has been recommended by NICE for use within defined NHS weight‑management services for individuals who meet specific eligibility criteria. Tirzepatide has been subject to separate NICE appraisal and phased commissioning decisions, meaning NHS access pathways currently differ.

This distinction explains why Wegovy® may be accessible through NHS services for some patients, while Mounjaro® is primarily accessed through private prescribing at present. The difference reflects commissioning policy rather than superiority or inferiority of either medicine.

3. Why might people be considering switching?

Several factors are currently influencing decisions in the UK:

NHS pathways – Some individuals wish to align their treatment with NHS‑commissioned services where eligible.

Cost considerations – In private care, Mounjaro® is generally more expensive than Wegovy®, which may influence affordability over time.

Supply and demand – Availability can fluctuate. Wegovy® supply in the UK has gradually stabilised, while global demand for tirzepatide remains high.

Future planning – Individuals who began treatment privately may consider alternatives that align more closely with long‑term NHS pathways.

4. Is there official switching guidance?

At present, there is no formal UK guidance on switching between Mounjaro® and Wegovy®. Manufacturers have not published standardised protocols, and NICE guidance does not provide instructions for transitioning between incretin‑based therapies.

As a result, any decision to switch must be made by a qualified prescriber, based on an individual’s medical history, previous response, side‑effect profile, and treatment goals.

5. Pharmacokinetics and overlap considerations

Semaglutide has a long half‑life of approximately one week, meaning the biologically active drug remains in the body for several weeks after the last dose. This persistence is clinically relevant when switching therapies, as overlapping effects may increase gastrointestinal side effects such as nausea or vomiting.

For this reason, prescribers often restart Wegovy® at a lower dose following tirzepatide use, or allow an appropriate interval before commencing treatment. These decisions require clinical judgement and monitoring rather than fixed rules.

6. What do emerging studies show?

Limited observational data, primarily from the United States, have described real‑world switching patterns between incretin‑based therapies. These reports suggest that:

• Individuals switching from Mounjaro® to Wegovy® frequently restart semaglutide at a lower dose.

• Side‑effect profiles appear broadly similar, without a clear increase in severe gastrointestinal events.

• Careful dose adjustment and monitoring remain central to tolerability.

It is important to emphasise that this evidence is descriptive rather than prescriptive. It illustrates what has been observed in practice but does not constitute clinical guidance.

7. Safety and suitability considerations

Neither Wegovy® nor Mounjaro® is suitable for everyone. Recognised contraindications include a personal or family history of medullary thyroid carcinoma, multiple endocrine neoplasia type 2, and certain gastrointestinal or endocrine conditions.

Commonly reported side effects include nausea, vomiting, constipation, and gallbladder‑related issues. These factors further underline why switching decisions should never be patient‑directed and must involve appropriate medical assessment.

8. Common misconceptions

A frequent misconception is that switching from Mounjaro® to Wegovy® represents a loss of effectiveness. In reality, individual response varies considerably, and some people achieve excellent outcomes on semaglutide.

Another misconception is that switching can be done seamlessly or independently. In practice, careful dose planning, monitoring, and follow‑up are essential to minimise side effects and ensure safety.

Key takeaways

Both Mounjaro® and Wegovy® are prescription medicines with strong evidence supporting their role in weight management.

Mounjaro® has demonstrated greater average weight loss in clinical trials, while Wegovy® is currently more accessible through NHS pathways in the UK.

There is no official switching protocol, and any change in treatment must be overseen by a qualified prescriber.

Final word

At Haus of Ästhetik, our role is to share reliable, evidence‑based information so individuals can better understand developments in the wellness and medical aesthetics space. We do not prescribe or supply these medicines.

If you are considering Mounjaro®, Wegovy®, or any similar treatment, please seek advice from a qualified UK healthcare professional who can assess suitability and guide safe decision‑making.

References

NICE. Tirzepatide for managing overweight and obesity (TA1026).

Wilding JPH et al. Once‑Weekly Semaglutide in Adults with Overweight or Obesity. New England Journal of Medicine. 2021.

Jastreboff AM et al. Tirzepatide Once Weekly for the Treatment of Obesity. New England Journal of Medicine. 2022.

Hvisdas CM et al. Characterisation of Interchanging Incretin Analogues. Endocrine Practice. 2025.

MHRA. Counterfeit medicine alerts and safety updates.

Disclaimer: This content is for educational purposes only and does not constitute medical advice, diagnosis, or treatment. Always consult a qualified healthcare professional before making decisions about prescription medicines.