Switching from Mounjaro to Wegovy
Clinical steps, rationale and monitoring
glp.spaceSwitching from Mounjaro (tirzepatide) to Wegovy (semaglutide) is a clinical decision that should be made under medical supervision.
While both medicines are effective for long‑term weight management, they work differently: Mounjaro is a dual GIP + GLP‑1 receptor agonist, whereas Wegovy is a single GLP‑1 receptor agonist with established cardiovascular outcome data. This guide outlines how the switch works, why it may be recommended, and what monitoring is required.
Why Consider Switching?
Some patients may benefit from switching to Wegovy for reasons including cardiovascular protection, tolerability, availability, or maintenance planning. Speak to your clinician to individualise decisions.
| Rationale | Description |
|---|---|
| Cardiovascular protection | Wegovy demonstrated a 20% reduction in MACE in patients with established CVD (SELECT, NEJM 2023). |
| Established safety record | Extensive long‑term data support tolerability and outcomes. |
| Side‑effect differences | Some patients tolerate GLP‑1–only therapy better if tirzepatide caused persistent GI symptoms. |
| Affordability or access | Depending on coverage and supply, Wegovy may be easier or cheaper to obtain. |
| Maintenance phase | After intensive weight‑loss on Mounjaro, some continue maintenance on Wegovy. |
| Medical suitability | Clinicians may prefer Wegovy for patients with CVD, kidney impairment, or other considerations. |
| Formulary rules | Certain UK insurers require a Wegovy trial before tirzepatide coverage. |
| Pregnancy planning | Both are contraindicated in pregnancy; clinicians may coordinate discontinuation and washout. |
How the Switching Process Works
- Medical consultation: Review response to Mounjaro, comorbidities, and goals.
- Stop Mounjaro: Usually after the final planned dose.
- Washout (~2–4 weeks): Allow tirzepatide to clear before starting Wegovy.
- Start Wegovy 0.25 mg weekly: Start low regardless of previous dose, then titrate.
- Gradual titration: Increase every ~4 weeks if tolerated: 0.25 → 0.5 → 1.0 → 1.7 → 2.4 mg.
- Monitoring: Track side‑effects, appetite, weight and relevant labs.
- Lifestyle continuity: Maintain diet, activity and hydration.
- Follow‑up: Reviews at 2–4–8–12 weeks and then every 3–6 months.
Always follow your prescriber’s schedule — not all patients require a washout, and timing may vary with kidney function and tolerance.
Who May Benefit from Switching
- Cardiovascular disease: needs proven MACE reduction
- GI intolerance to Mounjaro: persistent nausea/fullness despite stabilisation
- Weight‑maintenance phase: continuing with single‑GLP‑1 therapy
- Coverage/cost constraints: formulary or pricing issues
- Simplified regimen preference: predictable single‑mechanism titration
Not everyone should switch; some respond better to dual‑agonist therapy. Your prescriber will weigh benefits and risks.
Getting Started with Wegovy
- Form: once‑weekly prefilled injection pen.
- Starting dose: 0.25 mg weekly, increase every ~4 weeks as tolerated.
- Rotation: Rotate abdomen, thigh, upper arm; keep a consistent weekly schedule.
Your clinician may adjust timing and titration for tolerance, comorbidities or concomitant therapies.
Expected Outcomes (Clinical Data)
| Outcome | Typical result |
|---|---|
| Weight maintenance | ~15–17% loss over 68 weeks (STEP trials, NEJM 2021). |
| Cardiovascular outcomes | ~20% ↓ MACE in established CVD (SELECT, NEJM 2023). |
| HbA1c reduction | ~1.5–1.6% decrease (STEP‑2, T2D subgroup). |
| Metabolic health | Improved cholesterol, BP and insulin sensitivity. |
| Quality of life | Better physical function, energy and wellbeing scores. |
Typical timeline:
- 0–8 weeks: adjustment period (mild GI effects possible)
- 8–12 weeks: weight stabilisation
- 3–6 months: visible metabolic improvements
- 12 months+: maintenance phase
Safety and Monitoring
| Area | What to monitor |
|---|---|
| GI tolerance | Nausea, bloating, constipation — usually mild and transient |
| Blood glucose | Especially if diabetic or on insulin/sulfonylurea |
| Kidney & liver | Baseline and ~6‑monthly |
| Cardiovascular | BP / heart‑rate checks |
| Pancreatitis/gallbladder | Urgent review for severe abdominal pain |
| Weight trend | Track weekly; report rapid loss > 1 kg/week |
| Injection technique | Site rotation, storage, pen handling |
| Pregnancy prevention | Effective contraception required |
Contraindications:
- Personal/family history of medullary thyroid carcinoma or MEN‑2
- Active pancreatitis
- Pregnancy or breastfeeding
Laboratory & Clinical Follow‑Up (NICE / ADA)
| Parameter | Frequency | Purpose |
|---|---|---|
| Weight / BMI | Weekly early → monthly | Track trends |
| HbA1c | Every 3 months | Glycaemic control |
| Lipid profile | Every 6 months | CV risk |
| Liver & kidney | Every 6 months | Organ safety |
| BP / HR | Each visit | Cardiovascular status |
| Waist circumference | Quarterly | Central adiposity |
| Quality of life | Each review | Treatment satisfaction |
Evidence Summary
- STEP‑1: 14.9% mean weight loss vs 2.4% placebo at 68 weeks (NEJM 2021).
- STEP‑2: 9.6% loss and ~1.6% HbA1c reduction in T2D.
- STEP‑4: Sustained maintenance beyond 1 year.
- SELECT: ~20% reduction in MACE (CV benefit).
- Real‑world switching: Washout + gradual titration generally safe; most maintain weight with good tolerability.
Trusted Medical References
- Wilding JPH et al. STEP‑1 – Semaglutide in adults with overweight/obesity (NEJM 2021)
- Lincoff AM et al. SELECT – Semaglutide and CV outcomes (NEJM 2023)
- NICE TA875 – Semaglutide for managing overweight and obesity (2024)
- MHRA – Wegovy Summary of Product Characteristics (UK)
- ADA Standards of Care 2025 – GLP‑1 therapy guidance
- EASD/Consensus 2024 – GLP‑1 in obesity and cardiometabolic risk
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