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Switching from Mounjaro to Wegovy is possible but requires careful medical supervision. Mounjaro (tirzepatide) is a dual GIP/GLP-1 receptor agonist licensed for type 2 diabetes in the UK, whilst Wegovy (semaglutide) is a GLP-1 receptor agonist specifically licensed for weight management. Patients may consider switching due to availability issues, side effect profiles, clinical response, or prescribing preferences. However, these medications are not interchangeable—transitioning requires appropriate dose adjustment, timing considerations, and ongoing monitoring. This article explains the key differences between these medications, how to switch safely under clinical guidance, and relevant NHS and NICE recommendations for UK patients.
Quick Answer: You can switch from Mounjaro to Wegovy under medical supervision, typically starting Wegovy at the initial 0.25 mg dose after approximately one week.
Yes, it is possible to switch from Mounjaro to Wegovy, but this decision should always be made under the guidance of a healthcare professional. Mounjaro (tirzepatide) is a dual GIP/GLP-1 receptor agonist licensed for type 2 diabetes in the UK, while Wegovy (semaglutide) is a selective GLP-1 receptor agonist licensed specifically for weight management. For weight management, tirzepatide is licensed under the brand name Zepbound in the UK, not Mounjaro.
Patients may consider switching for various reasons, including:
Availability issues – supply constraints have affected both medications in the UK
Side effect profile – individual tolerance varies between different medications
Clinical response – some patients may achieve better weight loss or glycaemic control with one medication over another
Cost and access considerations – NHS eligibility criteria and private prescription costs may differ
Prescribing preferences – healthcare providers may have experience favouring one medication
It is essential to understand that switching between these medications is not simply a matter of substitution. The transition requires careful planning, appropriate dose adjustment, and monitoring for both efficacy and safety. Never switch medications without consulting your GP or specialist, as abrupt changes or incorrect dosing could lead to inadequate disease control, increased side effects, or other complications. Your healthcare provider will assess your individual circumstances, current treatment response, and medical history before recommending a switch.
Importantly, if you are taking Mounjaro for type 2 diabetes and considering switching, note that Wegovy is not licensed for glycaemic control. Your clinician may discuss alternatives such as Ozempic (semaglutide) which is licensed for diabetes management.
Whilst both Mounjaro and Wegovy are injectable medications, they have important pharmacological and clinical differences that healthcare professionals consider when prescribing.
Mechanism of Action: Mounjaro (tirzepatide) is a dual GIP/GLP-1 receptor agonist, meaning it activates both glucose-dependent insulinotropic polypeptide (GIP) and glucagon-like peptide-1 (GLP-1) receptors. This dual action may provide enhanced metabolic benefits. Wegovy (semaglutide) is a selective GLP-1 receptor agonist, acting solely on GLP-1 receptors to regulate appetite, slow gastric emptying, and improve insulin secretion.
Dosing and Administration: Mounjaro is administered once weekly via subcutaneous injection, with doses ranging from 2.5 mg (starting dose) up to 15 mg for maintenance. Wegovy is also given once weekly, starting at 0.25 mg and titrating up to a maximum maintenance dose of 2.4 mg. The titration schedules differ between the two medications, which is particularly relevant when switching.
Licensed Indications: In the UK, Mounjaro (tirzepatide) is licensed for type 2 diabetes management only. Tirzepatide for weight management is marketed as Zepbound. Wegovy (semaglutide) is specifically licensed for weight management in adults with a BMI ≥30 kg/m² or ≥27 kg/m² with at least one weight-related comorbidity.
NHS Access and NICE Guidance: NICE recommends Wegovy (TA875) for use within specialist weight management services, typically for a maximum of 2 years. Treatment is available for adults with a BMI of at least 35 kg/m² (or lower thresholds of 30-34.9 kg/m² for people from some ethnic backgrounds) and at least one weight-related comorbidity. Treatment should be discontinued if patients do not achieve at least 5% weight loss after 6 months at the maintenance dose.
Clinical Efficacy: While clinical trials suggest differences in weight loss outcomes between these medications, direct head-to-head comparative trials are limited. Individual response varies considerably, and some patients may respond better to one medication than the other. Side effect profiles are similar for both drugs, with gastrointestinal symptoms (nausea, vomiting, diarrhoea, constipation) being the most common adverse effects, though rates and severity may differ between individuals.
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Switching from Mounjaro to Wegovy requires a structured approach to ensure safety and maintain therapeutic benefit. This process must be supervised by your prescribing clinician, who will develop an individualised switching plan based on your current dose, treatment duration, and clinical response. There is no formal UK protocol for switching between these medications.
Timing and Washout Period: Both medications have relatively long half-lives (approximately 5 days for tirzepatide and 7 days for semaglutide), meaning they remain in the body for an extended period. Most healthcare providers recommend stopping Mounjaro and waiting approximately one week before initiating Wegovy. This approach minimises the risk of overlapping drug effects whilst avoiding a significant gap in treatment. There is no official guidance mandating a specific washout period, and some clinicians may recommend a direct switch depending on individual circumstances.
Dose Conversion Considerations: There is no established dose equivalence between Mounjaro and Wegovy. When switching, patients typically start Wegovy at the initial titration dose of 0.25 mg weekly, regardless of their previous Mounjaro dose. This conservative approach allows the body to adjust to the new medication and helps minimise gastrointestinal side effects. The dose is then gradually increased every 4 weeks following the standard Wegovy titration schedule (0.25 mg → 0.5 mg → 1 mg → 1.7 mg → 2.4 mg).
Special Precautions: If you are taking insulin or sulfonylureas alongside Mounjaro, your doctor may need to adjust these medications when switching to reduce the risk of hypoglycaemia. Ensure adequate hydration, particularly if you experience gastrointestinal side effects, as dehydration can affect kidney function. People with pre-existing renal impairment may require additional monitoring.
Monitoring and Follow-up: After switching, your healthcare provider should monitor:
Weight and BMI – to assess continued therapeutic response
Blood glucose levels – particularly important for patients with type 2 diabetes
Side effects – especially gastrointestinal symptoms during the initial weeks
Blood pressure and heart rate – as both medications can affect cardiovascular parameters
Patients should be advised to contact their GP if they experience severe or persistent side effects, including severe abdominal pain, persistent vomiting, signs of pancreatitis, or symptoms of thyroid tumours (neck lump, difficulty swallowing, persistent hoarseness). Suspected side effects should be reported via the MHRA Yellow Card scheme (yellowcard.mhra.gov.uk).
The National Institute for Health and Care Excellence (NICE) provides guidance on the use of GLP-1 receptor agonists for weight management, though specific recommendations on switching between different agents are limited. Healthcare professionals must therefore apply clinical judgement when managing medication transitions.
NICE Guidance on GLP-1 Receptor Agonists: NICE Technology Appraisal TA875 (published June 2023) recommends semaglutide (Wegovy) for weight management in adults with at least one weight-related comorbidity and:
A BMI of at least 35 kg/m² (or lower thresholds of 30-34.9 kg/m² for people from some ethnic backgrounds), or
A BMI of 30–34.9 kg/m² in specific circumstances
Importantly, NICE specifies that Wegovy should be used within specialist weight management services, typically for a maximum of 2 years. Treatment should be discontinued if patients do not achieve at least 5% weight loss after 6 months at the maintenance dose. NICE guidance emphasises that these medications should be used alongside a reduced-calorie diet and increased physical activity. At the time of writing, NICE guidance for tirzepatide (Zepbound) in weight management is still evolving.
NHS Prescribing Considerations: NHS England has issued guidance on the prescribing of GLP-1 receptor agonists in the context of supply constraints. When switching medications due to availability issues, the NHS recommends:
Prioritising clinical need – patients with the greatest clinical benefit should be prioritised
Shared decision-making – discussing the reasons for switching, potential benefits, and risks with patients
Appropriate monitoring – ensuring adequate follow-up after any medication change
Patient Safety Advice: The Medicines and Healthcare products Regulatory Agency (MHRA) has issued safety information regarding these medications. According to the Summary of Product Characteristics (SmPC), safety warnings include:
Thyroid C-cell tumours (observed in rodent studies; human relevance unknown)
Risk of pancreatitis
Gallbladder disorders including cholelithiasis
Patients switching between these medications should be counselled about these risks and advised to seek immediate medical attention if they develop:
Severe, persistent abdominal pain (potentially radiating to the back)
Persistent nausea and vomiting
Symptoms of gallstones (right upper abdominal pain, particularly after eating)
When to Seek Medical Advice: Patients should contact their GP or specialist if they experience inadequate weight loss after switching, intolerable side effects, or any concerning symptoms. Regular review appointments are essential to assess treatment efficacy, adjust doses appropriately, and ensure ongoing suitability for continued therapy. Your healthcare provider will work with you to determine the most appropriate medication and dosing strategy for your individual circumstances.
Most healthcare providers recommend waiting approximately one week after stopping Mounjaro before initiating Wegovy, though some clinicians may recommend a direct switch depending on individual circumstances. This timing accounts for the medications' long half-lives and minimises overlapping drug effects.
When switching from Mounjaro to Wegovy, patients typically start at the initial Wegovy titration dose of 0.25 mg weekly, regardless of their previous Mounjaro dose. There is no established dose equivalence between these medications, and the dose is gradually increased every 4 weeks following the standard titration schedule.
NHS access to Wegovy is determined by NICE guidance (TA875), which recommends it within specialist weight management services for adults with BMI ≥35 kg/m² (or lower thresholds for certain ethnic backgrounds) and weight-related comorbidities. Your GP or specialist will assess your eligibility and discuss switching options based on clinical need and local prescribing policies.
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DisclaimerThis content is not a substitute for professional medical advice, diagnosis, or treatment. Always consult a qualified healthcare professional with any medical questions or concerns. Use of the information is at your own risk, and we are not responsible for any consequences resulting from its use.
