Switching from Mounjaro to Wegovy – updated guidance for licensed use
Switching from Mounjaro to Wegovy is permitted under current UK product licensing and PGD protocols, provided that the transition follows retitration from the smallest authorised starting dose of the new medicine. Although clinicians in the UK sometimes use dose conversion to estimate an entry point, this is an unlicensed practice and lies strictly within the discretion of an independent prescriber. For PGD use, dose conversion tables must not be used to select a starting dose.
The update below reflects these requirements.
How the switch works under current licensed guidance
When switching from tirzepatide (Mounjaro) to semaglutide (Wegovy), the new medicine must be started at its lowest available dose to allow the gastrointestinal system to acclimatise gradually. This avoids excessive cumulative exposure during the period where the previous agent remains in circulation.
- Take the final Mounjaro dose as normal.
- Wait seven days.
- Start Wegovy at 0.25mg once weekly then escalate via the licensed dose ladder, allowing at least four weeks on each dose before increasing.
This approach follows the product licence and PGD protocol and is designed to reduce nausea, reflux, and other gastrointestinal effects related to slowed gastric emptying.
Switching at a higher semaglutide dose based on the prior tirzepatide strength is not supported within a PGD and would constitute an unlicensed decision requiring independent prescriber assessment, justification, and oversight.
Wegovy dose escalation (licensed and PGD compliant)
Wegovy should be titrated via the standard schedule:
0.25mg weekly -> then 0.5mg -> then 1mg -> then 1.7mg -> then 2.4mg (maintenance)
Each step should last at least four weeks and may be extended if side effects occur.
Direct dose matching between Mounjaro and Wegovy is not part of the product licence. The medicines are pharmacologically distinct and are therefore not interchangeable on a milligram for milligram basis.
Dose conversion table (unlicensed – independent prescriber discretion only)
In practice, some clinicians use approximate conversion to decide whether a higher semaglutide dose may be appropriate at initiation. This is not included in the licensed path and must not be used under a PGD. It is presented here solely as background reference for independent prescribing decisions.
Current Mounjaro dose -> Corresponding Wegovy dose used in unlicensed dose conversion:
- Mounjaro 2.5mg = Wegovy 0.25mg
- Mounjaro 5mg = Wegovy 0.5mg
- Mounjaro 7.5mg = Wegovy 0.5mg
- Mounjaro 10mg = Wegovy 1mg
- Mounjaro 12.5mg = Wegovy 1mg
- Mounjaro 15mg = Wegovy 1.7mg
Any decision to start Wegovy above 0.25mg based on these equivalences would require an independent prescriber to take full responsibility for the unlicensed approach, including clinical reasoning, risk management, and follow up arrangements.
What to expect after switching
Appetite effects may feel gentler at the earliest semaglutide dose. As Wegovy is titrated upward, hunger control usually strengthens. Some people experience temporary nausea, indigestion, or reflux. Smaller balanced meals, steady hydration, and slower eating habits can help. If symptoms persist, remaining at the current dose longer than four weeks is often effective.
Safety points
- Licensed and PGD pathways require starting Wegovy at 0.25mg after a seven day gap.
- Dose conversion is not part of the product licence and is only permissible when an independent prescriber formally authorises it.
- Report persistent vomiting, dehydration, or abdominal pain.
- Discuss any medicines that rely on predictable gastrointestinal absorption.
Key takeaways
- Switching between Mounjaro and Wegovy is allowed, but under a PGD the new medicine must be restarted from the smallest dose with standard retitration.
- Dose conversion tables are not part of licensed switching and may only be used by independent prescribers exercising clinical discretion.
- A seven day washout followed by Wegovy 0.25mg is the approved starting point.
- Gradual escalation helps limit gastrointestinal side effects.
