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
Free tracker included with every download this week
Do You Put Weight Back On After Mounjaro?
Weight regain after stopping Mounjaro is a common concern for people considering this prescription weight loss injection in the UK. The honest answer is that some people do regain weight after stopping, though outcomes vary significantly depending on whether lifestyle changes are maintained. NHS guidance emphasises that Mounjaro works best as part of a long-term weight management strategy, not as a standalone solution. Understanding what happens after treatment ends can help you make an informed decision about whether this weekly weight loss injection is right for your health goals.
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Calculate Your BMI Instantly
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.
What the Evidence Shows About Weight Regain
Clinical trial data shows mixed outcomes for weight after Mounjaro stops. In the SURMOUNT trials, participants who stopped the medication after achieving weight loss began regaining weight within weeks to months. However, those who maintained reduced-calorie eating and increased physical activity regained less weight than those who returned to previous eating habits. NHS guidance emphasises that medication is a tool, not a permanent fix — weight loss success depends on sustaining lifestyle changes alongside treatment.
- Participants who maintained diet and exercise regained approximately 30–50% of lost weight in the year after stopping
- Those who did not change eating habits often regained most or all weight within 12–18 months
- Some people experience improved appetite control even after stopping, suggesting partial benefit persistence
- Individual results vary significantly based on genetics, metabolism, and adherence to lifestyle changes
The MHRA approval for Mounjaro acknowledges this reality — the medication is prescribed as part of a comprehensive weight management programme, not as a replacement for dietary and physical activity changes.
Clinically BackedWeight Loss
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How It Works
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.
Free Weight Loss Tools & Guides
Everything you need to understand your weight, explore medication options, and track your progress — completely free.
NHS Approach to Long-Term Weight Management
NHS tier 3 specialist weight management services view Mounjaro as one component of sustained lifestyle change, not a permanent solution. Many services recommend continuing treatment longer if weight loss goals have been achieved and regain is a concern. Others recommend transition planning well before stopping — gradually introducing behaviour strategies while still on the medication to build confidence in maintaining loss independently.
- Work with your GP or specialist on a maintenance plan before stopping treatment
- Use our free BMI calculator and progress tracker to monitor weight stability after stopping
- Consider whether long-term treatment continuation might be appropriate for your individual situation
- Focus on building sustainable eating and activity patterns that can work without medication
- 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.
Will I definitely regain all the weight I lost on Mounjaro?
No — outcomes vary. Research shows that people who maintain reduced-calorie eating and regular physical activity regain significantly less weight than those who return to previous habits. Some people keep 50–70% of their weight loss long-term through lifestyle maintenance alone. Individual factors like genetics, metabolism, and adherence to behaviour change all influence regain rates.
Can I stay on Mounjaro indefinitely to prevent weight regain?
Long-term use is possible under NHS or private prescription, but requires ongoing clinical assessment. Your GP or specialist will review whether continued treatment remains appropriate for your health. Some people use Mounjaro long-term for weight management, while others use it short-term to establish lifestyle changes. This is a discussion to have with your prescriber.
What should I do before stopping Mounjaro to reduce regain risk?
Plan ahead with your GP or specialist. Establish strong eating and activity habits whilst still on medication — this builds confidence in maintaining changes independently. Track your weight using our free progress tracker. Consider gradually reducing doses rather than stopping abruptly. Ensure you have realistic expectations about what weight maintenance without medication requires.
Is Mounjaro worth starting if I might regain weight later?
Many people find significant value in the time weight loss gives them — improved health markers, reduced joint pain, better blood sugar control, and confidence gained. Weight regain is a concern, but not a reason to avoid treatment if you're eligible. The key is viewing Mounjaro as a tool to establish new habits, not a permanent solution, and being committed to lifestyle change.
How does Mounjaro compare to Wegovy for long-term weight management?
Both Mounjaro (tirzepatide) and Wegovy (semaglutide) show similar patterns — people who stop either medication and don't maintain lifestyle changes regain weight. Mounjaro's dual GIP and GLP-1 mechanism may provide slightly different appetite control, but long-term outcomes depend more on individual behaviour change than on which medication you use. Your prescriber can advise which is appropriate for you.
Ready to take control of your weight loss journey?
Start with a free BMI check, explore your GLP-1 options, or begin tracking your progress today. No sign-up. No cost. Just results.