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 Stopping Mounjaro?
Yes, some people do regain weight after stopping Mounjaro, though this varies significantly between individuals. Weight regain isn't automatic — it depends on whether lifestyle changes persist after treatment ends. Research shows that maintaining the dietary and physical activity habits built during Mounjaro treatment is crucial for long-term weight stability. Your GP can help you plan a sustainable approach to weight management beyond your prescription weight loss injection.
10,000+ calculations today · NHS-aligned thresholds · 100% free
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 Happens to Weight After Mounjaro Treatment Ends?
When you stop Mounjaro (tirzepatide), the appetite-suppressing effects of the weekly weight loss injection gradually fade as the medication leaves your system. This typically happens over 4–8 weeks after your final dose. Without the pharmaceutical support that helped reduce hunger and food cravings, many people find it easier to eat larger portions again. However, weight regain is not inevitable — it depends entirely on whether you maintain the lifestyle changes (reduced calorie intake and increased physical activity) that you developed while using Mounjaro as part of your prescription weight loss journey. Some people maintain their weight loss without further treatment, while others regain some or all of the weight. This variation reflects individual differences in metabolism, eating behaviours, and long-term adherence to healthier habits. Your GP can discuss strategies to protect your weight loss after treatment ends.
Clinically BackedWeight Loss
No appointments. No waiting rooms. Just care — from a UK-regulated online pharmacy.
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.
Managing Weight Long-Term After Mounjaro
The transition off Mounjaro is a critical time for establishing sustainable weight management habits. Consider these evidence-based approaches: continue the reduced-calorie eating patterns and increased physical activity that worked during treatment, use our free GLP-1 weight loss calculator to review what your treatment achieved, track your progress regularly with our progress tracker to spot early weight changes, and maintain regular GP appointments to discuss maintenance strategies. Some patients benefit from returning to Mounjaro or exploring alternative weight management support if they struggle to maintain weight loss independently. The NHS recommends aiming for gradual weight loss of 0.5–1 kg per week, and this same principle applies to weight maintenance — small, consistent changes are more sustainable than dramatic restrictions. Your GP can personalise advice based on your individual circumstances and health profile.
- 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 weight when I stop Mounjaro?
No — weight regain is not automatic. Some people maintain their weight loss after stopping, while others regain some weight. It depends on whether you sustain the dietary and lifestyle changes you made during treatment. Individual results vary significantly based on metabolism, eating habits, and ongoing activity levels. Your GP can help you develop a maintenance strategy.
How long after stopping Mounjaro does weight come back?
Weight regain typically begins within 4–8 weeks as the medication leaves your system and appetite-suppressing effects fade. However, the timeline and amount of regain vary widely between individuals. Some people maintain stable weight for months, while others notice gradual increases earlier. Regular monitoring helps identify trends early.
Can I restart Mounjaro if I regain weight after stopping?
Yes, restarting Mounjaro is an option if you've regained weight and meet the eligibility criteria. This would require another clinical assessment from your prescriber or GP. Some people use Mounjaro cyclically or long-term depending on their individual needs and prescriber recommendations. Discuss your options with your healthcare provider.
What's the difference between using Mounjaro vs Wegovy for preventing weight regain?
Both are prescription-only weight loss injections available in the UK. Mounjaro is a dual GIP/GLP-1 agonist (up to 15 mg weekly), while Wegovy is a GLP-1-only agonist (up to 2.4 mg weekly). Average weight loss differs slightly between them, but long-term weight regain after stopping depends more on lifestyle maintenance than the medication type. Your prescriber can advise which suits you better.
Is there anything that helps prevent weight regain after Mounjaro under NICE guidance?
NICE guidance emphasises combining medication with sustainable lifestyle changes — reduced calorie intake, increased physical activity, and behavioural support. After treatment ends, maintaining these habits is essential. Use our free BMI calculator and weight converter to track progress. Some people benefit from structured weight management programmes, GP support, or returning to tier 3 NHS specialist services for ongoing guidance.
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.