Changing GLP-1 in the UK: Switching from Mounjaro to Wegovy

By Dr Mark Larkin, PhD, Medical Director, Pharmacy Price Hound

Introduction

The recent price shift for Mounjaro (tirzepatide) has left many UK patients facing difficult choices. For those managing type 2 diabetes or obesity, the cost of private prescriptions can be as stressful as the condition itself.

One question arises more often than any other: is it possible, and safe, to switch to another GLP-1 receptor agonist, such as semaglutide (Wegovy/Ozempic)?

At Pharmacy Price Hound, our role is not to prescribe, but to give patients transparent information about costs, safety principles, and the commercial pressures shaping the market.

October 2025 Price Snapshot

Key trend: Starter packs remain the most affordable entry point, but ongoing maintenance doses can reach £250-£300 per month. For many patients, this is equivalent to a monthly car payment, a reminder that treatment decisions are as much about economics as healthcare.

The Medical Imperative: Why Molecular Class and Dosing Matter

Mounjaro (tirzepatide) is not just another GLP-1. It is a first-in-class dual agonist, meaning that it targets both GLP-1 and GIP pathways, which makes it distinct from semaglutide (Wegovy/Ozempic) or liraglutide (Saxenda), which targets just GLP-1.

This difference matters for two reasons:

• Differential efficacy: Clinical trials show Mounjaro can outperform single-pathway GLP-1 drugs in blood sugar control and weight reduction. Switching may mean reduced potency.
• Side effect tolerance: Tolerating Mounjaro doesn’t guarantee tolerating semaglutide. Patients can find side effects return, or worsen, if moved across.

That leads to the most critical safety principle: dose titration. 

Dose Titration: Start Low and Go Slow

Mounjaro should start at lowest dose (see: MHRA Product Information Leaflet: https://www.medicines.org.uk/emc/files/pil.15481.pdf). Dose can be increased if there are no problems like side effects.

No matter your previous Mounjaro dose, switching to Wegovy or Ozempic requires starting again at the lowest recommended dose. This is not caution for its own sake, but the explicit protocol set by the MHRA: for semaglutide (Wegovy), MHRA approved escalation in their Product Information Leaflet (https://www.medicines.org.uk/emc/files/pil.13800.pdf is:

• Month 1: 0.25mg once weekly
• Month 2: 0.5mg once weekly
• Month 3: 1.0mg once weekly
• Month 4: 1.7mg once weekly
• Month 5 onwards: 2.4mg once weekly (maintenance dose)

So jumping ahead based on a previous Mounjaro dose may be unsafe. These are different molecules, and tolerance does not transfer across.

In short: even if you were on the highest dose of Mounjaro, Wegovy or Ozempic requires a fresh start at 0.25mg.

Market Trend & Ethical Dilemmas

The UK’s private pharmacy sector has expanded access to GLP-1 medicines, but it also introduces commercial incentives. Higher doses generate higher dispensing fees, which may tempt less scrupulous providers to skip the recommended titration schedule.

This is why patients must be vigilant. If a prescriber suggests starting semaglutide above 0.25mg, you should ask for clear clinical justification.

Many providers operate with integrity, but the financial incentive exists. Patients should remember: the safest providers are those who carefully consider side effects and dose escalation, not just the price tag.

A Framework for a Safe Switch

If you and your clinician decide a switch is necessary:

Seek professional guidance – never attempt to switch without clinical supervision.
Insist on the starter dose – regardless of prior Mounjaro use.
Manage expectations – hunger or blood glucose shifts may return temporarily.
Track your symptoms – appetite, side effects, mood, and blood sugar.
Be patient – the five-month titration schedule is deliberate and protective.

Dr Mark Larkin, PhD, Medical Director, Pharmacy Price Hound

“Switching between Mounjaro and semaglutide is not a straight line. These are different molecules, and the safest approach is to reset and titrate carefully. Skipping that step risks both effectiveness and patient safety.”

FAQs

Can I switch directly from Mounjaro to Wegovy?
As they are different molecules, they may have different side effects, so restarting at the semaglutide starter dose is the safest approach.

Why do I need to titrate slowly?
The protocol reduces side effects and favours long-term tolerability.

Is switching covered by the NHS?
Only in specific clinics, under strict criteria. Medical supervision and advice is vital.

Are online pharmacies safe for switching?
Yes, if they are GPhC-registered and follow MHRA guidance. Always ask questions if a provider suggests skipping doses.

Conclusion: Advocacy Matters

Switching between GLP-1 medicines is more than a cost decision. It is a clinical, ethical, and financial challenge. Patients must be prepared to ask difficult questions, prioritise safety, and recognise that treatment progress is a marathon, not a sprint.

At Pharmacy Price Hound, we believe that informed patients are safer patients. By combining evidence-based medical practice with transparent price comparisons, we aim to help patients make confident, safe choices.

Disclaimer

This article is for informational purposes only. It does not provide medical advice. Patients should always consult a qualified prescriber before starting, stopping, or switching medication.

Author & Sources

Author: Dr Mark Larkin, PhD

• Medical Director, Pharmacy Price Hound
• Academic publications in health economics

Primary Sources:

• NICE NG28 Diabetes Guidelines
• NHS Weight Management Services
• MHRA Medicines Register

Dr Fox, Chemist4U, Oxford Online, Superdrug Online pharmacy pricing (October 2025)