Switching GLP-1 Medications: Complete UK Guide
Thinking about switching from Ozempic to Wegovy, or Wegovy to Mounjaro? This guide explains when and how to switch GLP-1 medications, dose equivalence, what to expect during the transition, and important considerations for UK patients.
Always Consult Your Prescriber
Switching between GLP-1 medications should only be done under medical supervision. This guide provides general information, but your prescriber will determine the appropriate approach based on your individual circumstances.
When to Consider Switching
Switching GLP-1 medications may be appropriate in certain situations. Here are the main reasons people consider changing their treatment:
Inadequate weight loss
Not achieving your weight loss goals despite being on maximum tolerated dose for several months
Intolerable side effects
Persistent GI side effects that don't improve with time or dose adjustments
Supply issues
Your current medication is unavailable due to shortage (less common in 2025)
Change in treatment goals
Moving from diabetes management to weight-focused treatment or vice versa
Cost considerations
Finding a more affordable option, such as generic liraglutide
Common Switch Scenarios
Here are the most common medication switches and what to expect:
| From | To | Common Reason | Approach |
|---|---|---|---|
| Ozempic | Wegovy | Licensed for weight loss | Same ingredient, equivalent dose |
| Ozempic | Mounjaro | Better weight loss results | Different drug, restart low |
| Wegovy | Mounjaro | Plateau or side effects | Different drug, restart low |
| Saxenda | Wegovy | Better efficacy | Different drug, start low |
| Any GLP-1 | Saxenda | Cost or availability | Different schedule |
Switching from Ozempic to Wegovy
This is the most straightforward switch because both medications contain the same active ingredient (semaglutide). The main difference is the approved indication and maximum dose.
- Licensed for type 2 diabetes
- Maximum dose: 1mg weekly
- Weight loss: ~5-6% average
- Licensed for weight management
- Maximum dose: 2.4mg weekly
- Weight loss: ~15% average
- 1Take your last Ozempic dose as normal
- 2On your next injection day (7 days later), start Wegovy
- 3Your prescriber may start you at an equivalent dose (e.g., Ozempic 1mg to Wegovy 1mg)
- 4Continue escalating Wegovy up to 2.4mg as tolerated
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Switching to Mounjaro (Tirzepatide)
Switching from semaglutide (Ozempic/Wegovy) to tirzepatide (Mounjaro) is more complex because they are different medications with different mechanisms of action.
Key Differences
- Semaglutide: GLP-1 receptor agonist only
- Tirzepatide: Dual GLP-1 + GIP receptor agonist
- 1Take your last semaglutide dose as normal
- 2On your next injection day (7 days later), start Mounjaro at 2.5mg
- 3Start at 2.5mg regardless of your previous semaglutide dose
- 4Follow the standard Mounjaro escalation: 2.5mg → 5mg → 7.5mg → 10mg → 12.5mg → 15mg
- 5Your prescriber may escalate faster if you tolerated high-dose semaglutide well
Expect GI Side Effects
Even if you tolerated semaglutide well, you may experience nausea, vomiting, or diarrhoea when starting tirzepatide. This is normal as your body adjusts to the new medication. Side effects typically improve over 2-4 weeks.
Dose Equivalence Guide
While there's no official dose equivalence between semaglutide and tirzepatide, this table provides approximate guidance based on clinical data and prescribing experience:
| Ozempic | Wegovy | Mounjaro | Note |
|---|---|---|---|
| 0.25mg | 0.25mg | 2.5mg (start dose) | Initiation doses |
| 0.5mg | 0.5mg | 2.5-5mg | Early escalation |
| 1mg | 1mg | 5-7.5mg | Moderate doses |
| N/A | 1.7mg | 7.5-10mg | Higher doses |
| N/A | 2.4mg | 10-15mg | Maximum doses |
Important: These are approximate equivalences only. Your prescriber will determine the appropriate dosing based on your individual response and tolerance.
What to Expect When Switching
First 2 Weeks
You may experience a return of GI side effects similar to when you first started GLP-1 treatment. Appetite suppression may be different - some people find one medication works better than another for reducing cravings.
Weeks 2-8
Side effects should gradually improve. You'll be in the dose escalation phase if switching to a new medication. Weight loss may pause temporarily as your body adjusts, or you may see renewed weight loss if the new medication suits you better.
After 12 Weeks
By this point, you should be able to assess whether the switch was beneficial. You'll likely be on a maintenance dose and can compare your response to your previous medication. Discuss progress with your prescriber at follow-up appointments.
When Switching May Not Be Appropriate
Consider NOT Switching If:
- • You're still in the early stages of treatment (less than 4-6 months)
- • You haven't reached your maximum tolerated dose yet
- • Your weight plateau is temporary (less than 2-3 months)
- • You're making good progress on your current medication
- • The switch is driven by cost alone without medical justification
- • You have contraindications to the new medication
NHS Switching Policies
If you're on NHS treatment, switching policies may vary:
- Formulary restrictions: Your NHS area may have preferred medications. Switching may require clinical justification.
- Shared care: If a specialist initiated your treatment, switching may need their input or approval.
- Documentation: Your prescriber will need to document the reason for switching in your medical records.
- Supply issues: If switching due to shortage, this is usually straightforward once alternatives are available.
Frequently Asked Questions
Related Guides
References & Sources
- Novo Nordisk. Wegovy (semaglutide) Summary of Product Characteristics. MHRA.
- Eli Lilly. Mounjaro (tirzepatide) Summary of Product Characteristics. MHRA.
- NICE. Technology Appraisal Guidance on semaglutide and tirzepatide for weight management.
- Frías JP, et al. Tirzepatide versus Semaglutide Once Weekly in Patients with Type 2 Diabetes. NEJM 2021.
Medical Disclaimer
This information is provided for educational purposes only and is not intended as medical advice. Switching between GLP-1 medications should only be done under the supervision of a qualified healthcare professional. Always consult your prescriber before making any changes to your medication regimen.
Last updated: December 2025
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