The UK's most complete GLP-1 guide
Every Question Answered. Every Side Effect Explained.
- How GLP-1 medications work
- Mounjaro vs Wegovy compared
- Injection instructions
- Side effects & solutions
- What to eat on treatment
- FAQs answered
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When To Stop Mounjaro: Comparison With Wegovy
Deciding when to stop Mounjaro depends on your individual health goals, side effects, and how you respond to the medication — a decision that must be made with your prescriber. Both Mounjaro (tirzepatide) and Wegovy (semaglutide) are prescription-only weight management injections available in the UK, but they work differently and may suit different people. This guide compares when and why you might stop one medication versus the other, based on clinical evidence and UK prescribing practice.
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Enter your height and weight below. Supports both imperial (stone & lbs) and metric (kg). Results include NHS category, healthy weight range, and ethnicity adjustments.
What Is BMI and Why Does It Matter?
Body Mass Index (BMI) is the most widely used screening tool for assessing whether your weight falls within a healthy range. Used by the NHS, GPs, and weight management services across the UK, BMI provides a quick snapshot of your weight relative to your height. The formula is simple: your weight in kilograms divided by your height in metres squared (kg/m²).
While BMI isn't a perfect measure — it doesn't account for muscle mass, bone density, or fat distribution — it remains the standard first step in identifying potential weight-related health risks including type 2 diabetes, cardiovascular disease, high blood pressure, and certain cancers.
The NHS also recommends adjusted thresholds for people of South Asian, Chinese, or Black African heritage — a BMI of 23 or above is classified as overweight, and 27.5 as obese. Our calculator includes this adjustment as a one-click toggle.
Mounjaro vs Wegovy: Mechanism and Trial Data
Mounjaro (tirzepatide) is a dual GIP and GLP-1 receptor agonist, meaning it activates two natural hormone pathways to regulate appetite and blood sugar. The SURMOUNT-1 clinical trial showed participants on the maximum 15 mg dose lost an average of 20.9% of their body weight over 72 weeks, alongside a reduced-calorie diet and increased physical activity.
Wegovy (semaglutide) is a GLP-1-only receptor agonist — it activates one hormone pathway. The STEP-1 clinical trial showed participants on 2.4 mg lost an average of 14.9% of body weight over 68 weeks under similar conditions. Both are once-weekly injections, but Mounjaro dose titration starts at 2.5 mg and escalates to 15 mg maximum, whilst Wegovy starts at 0.25 mg and escalates to 2.4 mg. Individual results vary significantly depending on lifestyle, genetics, and how your body responds.
Neither medication is right or wrong — your UK prescriber will assess which suits your health profile, medical history, and weight management goals during your initial clinical assessment.
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Enter your height and weight in our free calculator. Get your BMI, NHS category, healthy weight range, and ethnicity-adjusted thresholds instantly.
If your BMI suggests you're overweight or obese, explore our GLP-1 calculators to project potential weight loss on Mounjaro or Wegovy.
Use our progress tracker to log your weight weekly, visualise your journey with charts, and stay motivated — all stored privately in your browser.
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When To Stop Either Medication: Individual Suitability and Prescriber Decision
You may consider stopping Mounjaro or Wegovy if: intolerable side effects develop that don't improve after dose adjustment, you reach your weight loss goal and wish to maintain with lifestyle changes alone, or your health circumstances change significantly. However, stopping should always be discussed with your prescriber — abrupt cessation can lead to appetite return and rapid weight regain. Some people pause treatment and restart later, whilst others continue long-term for sustained weight management.
Use our free GLP-1 weight loss calculator to understand potential outcomes at different doses, and discuss realistic expectations with your prescriber. They will assess whether continued treatment, a dose reduction, or a temporary pause is most appropriate for you. Both medications require ongoing prescriber monitoring throughout treatment.
Your GP or licensed prescriber will consider your individual suitability for each medication based on your BMI, medical history, side effect tolerance, and weight loss response. Some people respond better to Mounjaro's dual mechanism, whilst others find Wegovy effective at lower doses. Switching between medications is possible but requires clinical guidance — do not attempt self-switching. Use the BMI calculator on this page to check whether you meet current UK eligibility criteria (BMI 30+ or 27–29.9 with weight-related health conditions), then discuss medication options with your prescriber.
- Dual GIP/GLP-1 receptor agonist
- Up to 22.5% body weight loss (SURMOUNT-1)
- Weekly injection, dose escalation over 20+ weeks
- Available via private prescription in the UK
- Doses: 2.5mg → 5mg → 7.5mg → 10mg → 12.5mg → 15mg
- GLP-1 receptor agonist
- Up to 15–17% body weight loss (STEP trials)
- Weekly injection, 5-step dose escalation
- NHS & private prescription available
- Doses: 0.25mg → 0.5mg → 1mg → 1.7mg → 2.4mg
Mounjaro vs Wegovy: Head-to-Head
A side-by-side comparison of the two most popular GLP-1 weight loss medications available in the UK.
| Feature | Mounjaro | Wegovy |
|---|---|---|
| Drug class | Dual GIP/GLP-1 agonist | GLP-1 agonist |
| Active ingredient | Tirzepatide | Semaglutide |
| Avg. weight loss | 15–22.5% | 12–17% |
| Key trial | SURMOUNT-1 (2022) | STEP 1 (2021) |
| Max dose | 15 mg weekly | 2.4 mg weekly |
| Escalation period | 20–32 weeks | 16–20 weeks |
| Administration | Weekly injection (pen) | Weekly injection (pen) |
| NHS availability | Private prescription only | NHS & private |
| Approx. private cost | £150–£250/month | £150–£300/month |
| Common side effects | Nausea, diarrhoea, constipation | Nausea, vomiting, diarrhoea |
Data sourced from SURMOUNT-1 and STEP 1 clinical trials. Costs are approximate and vary by provider. Always consult a prescriber.
Am I Eligible for Weight Loss Medication?
In the UK, eligibility for GLP-1 weight loss medications like Mounjaro and Wegovy is based on your BMI and overall health profile.
- BMI of 30 or above (obese)
- Age 18 or over
- No contraindicated conditions
- Committed to lifestyle changes
- BMI of 27 or above
- Plus type 2 diabetes
- Or high blood pressure
- Or obstructive sleep apnoea
Use our BMI calculator to check whether your BMI falls within the eligible range.
How We Built These Tools
Every calculator and guide on myweightcheck is built with accuracy and transparency in mind. Our BMI calculator uses the standard WHO formula with NHS-aligned category thresholds. Our GLP-1 projections are modelled on published clinical trial data from SURMOUNT and STEP studies.
All data stays on your device. We don't require sign-ups, and we don't store your health information on any server. Your progress tracker saves data locally in your browser using localStorage, so only you can see it.
We're based in the UK and our tools are designed specifically for UK users — supporting stone & lbs by default, referencing NHS guidelines, using NICE-approved medication data, and linking to GPhC-registered pharmacies.
Frequently Asked Questions
Common questions about BMI, weight loss medications, and our free UK tools.
How long should I stay on Mounjaro before stopping?
There is no fixed duration. Many people continue Mounjaro for months or years if it works well. Your prescriber will discuss stopping after you reach your weight loss goal or if side effects become intolerable. Stopping is a clinical decision made together with your prescriber — not something to do without guidance, as appetite may return quickly.
Can I switch from Mounjaro to Wegovy?
Yes, switching is possible but requires prescriber management. There is no official conversion chart, though approximate equivalences exist (for example, Mounjaro 10 mg is roughly equivalent to Wegovy 1.7 mg). Your prescriber will manage the transition carefully to avoid appetite rebound. Switching should be considered if you experience significant side effects or poor response to Mounjaro.
What happens to weight when you stop Mounjaro or Wegovy?
Clinical data shows weight often returns fairly quickly after stopping — some people regain 50% or more of lost weight within weeks. This is because appetite hormones normalise. Your prescriber may discuss continuing long-term treatment, reducing to a maintenance dose, or a structured pause plan to minimise regain whilst maintaining lifestyle changes.
Does NICE recommend stopping either medication at a specific point?
NICE guidance approves both Mounjaro and Wegovy for UK weight management but does not specify a stopping point. Treatment duration is individualised. NICE recommends ongoing prescriber monitoring and discussion about continuing, pausing, or stopping based on your response, side effects, and health goals.
Which medication is easier to stop — Mounjaro or Wegovy?
Both carry similar appetite rebound risk when stopped. Neither is inherently "easier" to stop. The better medication for you is the one you tolerate well and that helps you reach your goals. Stopping decisions are based on individual response, not the drug itself. Discuss a structured cessation plan with your prescriber rather than stopping abruptly. ```
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