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 People Put Weight Back On After Mounjaro?
Weight regain after stopping Mounjaro is a realistic possibility that many people face, though individual experiences vary significantly. Clinical evidence suggests that without continued medication or sustained lifestyle changes, people can regain some or all of the weight they lost. This is not unique to Mounjaro — it's a common pattern with most weight loss treatments. Understanding what the research shows, how Mounjaro compares to alternatives like Wegovy, and how to maintain results is essential for anyone considering this weekly weight loss injection in the UK.
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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 Clinical Trials Show About Weight Regain
The SURMOUNT clinical trials tracked Mounjaro users for around 72 weeks, showing average weight loss of 15–21% body weight depending on dose. However, what happens after stopping treatment is equally important. When participants in weight loss studies discontinue medications without lifestyle changes, weight regain typically occurs over months.
- Post-treatment regain: Research suggests many people regain 25–50% of lost weight within 12 months of stopping GLP-1 or dual GIP/GLP-1 therapy
- Mechanism: As medication levels drop, appetite hormones return to baseline, reducing feelings of fullness and increasing food cravings
- Mounjaro vs Wegovy: Both medications (a dual GIP+GLP-1 agonist vs GLP-1-only) show similar regain patterns when stopped — individual outcomes vary based on lifestyle factors
- Long-term use: Many people continue Mounjaro or switch to alternatives indefinitely to maintain weight loss, similar to managing other chronic health conditions
The key is that weight loss from a weekly weight loss injection is not permanent unless supported by sustained dietary changes and physical activity.
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.
How to Minimise Weight Regain After Mounjaro
Preventing weight regain requires a proactive approach before and after stopping Mounjaro. Use the time on medication to build sustainable eating and exercise habits that can continue long-term. Track your progress using a weight tracker to identify patterns and early signs of regain. Work with your prescriber or GP on a structured plan for coming off the medication if you choose to stop.
- Dietary foundation: Focus on protein intake, whole foods, and portion control during treatment — these habits should continue after stopping
- Physical activity: Build a regular exercise routine now, not after stopping medication
- Ongoing support: Consider structured weight management programmes or ongoing clinical support through NHS tier 3 services where available
- Prescription context: In the UK, Mounjaro is available via NHS specialist services or private prescription — discuss long-term plans 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.
Is weight regain after Mounjaro inevitable?
No, but it is common without continued effort. Weight regain depends on whether you maintain the dietary and exercise habits you developed during treatment. Some people successfully keep weight off long-term; others regain weight. Your individual success depends on lifestyle changes, not just the medication.
How quickly do people regain weight after stopping Mounjaro?
Weight regain typically begins within weeks of stopping and can continue over several months. The speed varies based on diet, activity level, and individual metabolism. Some people regain weight steadily; others experience rapid regain initially then plateau.
Does Wegovy have the same weight regain risk as Mounjaro?
Yes, both medications show similar regain patterns when stopped. Wegovy is a GLP-1-only injection while Mounjaro is a dual GIP+GLP-1 agonist, but both work by appetite suppression — when medication stops, appetite returns and regain becomes likely without lifestyle maintenance.
Can you stay on Mounjaro long-term to prevent weight regain?
Yes. Many people continue Mounjaro indefinitely, similar to managing other chronic conditions like diabetes. Your UK prescriber can discuss whether long-term use is appropriate for you based on your health and weight management goals.
What's the best way to prevent weight regain after Mounjaro?
Build sustainable eating habits, establish regular physical activity, and work with your GP or a weight management programme before stopping medication. Use a progress tracker to monitor changes early. Consider whether continuing treatment is right for you — discuss this with your prescriber.
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.