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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What Happens When You Stop Taking Mounjaro?
When you stop taking Mounjaro (tirzepatide), your body gradually returns to its previous appetite and metabolic state as the medication leaves your system. Weight regain is common after stopping, though the amount varies between individuals. Understanding what to expect — and how this compares to stopping Wegovy — can help you plan your weight management long-term. Both medications work differently, so their discontinuation effects differ. This guide explains the facts based on clinical evidence and NHS guidance.
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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.
What Clinical Evidence Shows About Stopping Mounjaro
When you discontinue Mounjaro, the tirzepatide leaves your body within approximately 4–5 weeks (one complete injection cycle after your last dose). During this period, the dual GIP and GLP-1 hormone pathway effects gradually diminish, meaning appetite suppression and fullness signals decline progressively.
Clinical trial data and real-world evidence show:
- Weight regain typically begins 1–2 weeks after stopping
- On average, participants regain 50–70% of lost weight within 6–12 months if lifestyle changes are not maintained
- Nausea and appetite-related side effects usually resolve within 2–3 weeks
- Blood sugar control improvements (for those with type 2 diabetes) may also reverse
- Individual results vary significantly depending on baseline diet and activity levels
The Mounjaro SURMOUNT trials showed weight regain occurs when medication is stopped — but participants who maintained reduced-calorie intake and exercise retained more of their weight loss.
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Three simple steps to understand your weight and take action.
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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Mounjaro vs Wegovy: How Stopping Compares
While both Mounjaro and Wegovy are once-weekly injectables, they use different mechanisms, which affects discontinuation patterns. Wegovy (semaglutide) is a GLP-1 agonist only; Mounjaro activates both GIP and GLP-1 pathways. This means Mounjaro's dual action may support greater appetite reduction during treatment — but weight regain patterns are similar when stopped.
Both medications share comparable discontinuation timelines: appetite returns over 3–4 weeks as the injection wears off, and weight regain occurs without sustained lifestyle changes. Clinical evidence suggests weight regain is comparable between the two if diet and exercise aren't maintained. Your GP or prescriber can advise which is more suitable for your individual situation based on medical history, lifestyle, and treatment goals.
- 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 quickly does weight return after stopping Mounjaro?
Weight regain typically begins 1–2 weeks after your final injection as tirzepatide leaves your system. Most weight regain occurs over 3–6 months if diet and activity don't change. Some people retain more loss if they maintain reduced-calorie intake and exercise habits established during treatment.
Will my appetite return to normal after stopping?
Yes. Appetite suppression effects diminish over 3–4 weeks as the medication clears your body. Hunger and food cravings gradually return to pre-treatment levels. This is why maintaining the healthier eating habits developed during treatment is important for long-term weight management.
Is it safe to stop Mounjaro suddenly, or do I need to taper?
Mounjaro can be stopped without tapering — there is no withdrawal syndrome. However, always discuss stopping with your GP or prescriber. They can advise whether a gradual stop is appropriate for your situation and discuss weight management strategies going forward.
How does stopping Mounjaro compare to stopping Wegovy?
Both medications show similar weight regain patterns when discontinued because appetite returns as the medication leaves your system. Wegovy (semaglutide, GLP-1 only) and Mounjaro (tirzepatide, dual GIP+GLP-1) have comparable discontinuation timelines. Results vary individually based on lifestyle maintenance.
Can I restart Mounjaro if weight returns after stopping?
Yes, Mounjaro can be restarted following clinical assessment with your prescriber. Some people use it intermittently or cyclically, though long-term continuous use is typically more effective. Your GP can discuss the best approach for your weight management goals.
Ready to take control of your weight loss journey?
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