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 Gain Weight After Stopping Mounjaro?
Yes, some people do regain weight after stopping Mounjaro (tirzepatide), but this isn't inevitable. Weight regain depends on whether you maintain the lifestyle changes — reduced calorie intake and increased physical activity — that supported your initial weight loss. Research shows that without continued dietary and exercise habits, weight often returns within months. However, many people successfully maintain their loss long-term by sustaining these healthy changes alongside ongoing support from their GP or healthcare provider.
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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 Happens When You Stop Taking Mounjaro
Mounjaro works by activating GIP and GLP-1 hormone pathways, which suppress appetite and help you feel fuller after eating. When you stop the weekly weight loss injection, these hormonal effects gradually diminish over several days. Your appetite typically returns to pre-treatment levels within 1–2 weeks. This means you may feel hungry sooner and eat larger portions — potentially leading to weight regain if you don't maintain the dietary habits you developed during treatment.
Clinical data suggests that without ongoing lifestyle support, approximately 30–50% of weight lost can return within the first year after stopping. However, people who continue calorie deficit eating and regular physical activity often maintain 50–80% of their weight loss. The key factor is habit formation — if Mounjaro helped you develop sustainable eating patterns, you're more likely to keep weight off. Your GP can discuss ongoing support strategies, including whether continuing treatment might be appropriate for you.
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.
How to Prevent Weight Regain After Stopping Treatment
Before stopping Mounjaro, work with your healthcare provider to develop a weight maintenance plan. This should include specific dietary strategies you'll follow — such as meal planning, portion control, or a structured diet approach — and a realistic exercise routine you can sustain. Many people find it helpful to track their food intake and weight during the transition. Use our free progress tracker to log your weight regularly and spot early signs of regain so you can adjust habits quickly.
Consider whether a gradual reduction in Mounjaro dose (tapering) rather than stopping abruptly might work better for you — discuss this with your prescriber. Some people benefit from ongoing GP support, referral to a tier 3 NHS weight management service, or working with a registered dietitian. Never stop Mounjaro suddenly without medical guidance, and always have a clear maintenance plan before your treatment ends.
- 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 gain weight back after stopping Mounjaro?
No — weight regain isn't automatic. People who maintain reduced calorie intake and regular physical activity often keep 50–80% of their weight loss long-term. Success depends on sustaining the healthy habits you developed during treatment, not the medication itself. Your GP can help you plan for maintenance.
How quickly does weight return after stopping?
Appetite typically returns within 1–2 weeks as the medication leaves your system. Gradual weight regain may begin within 2–4 weeks if you don't maintain your dietary and exercise habits. Some people notice changes within days; others take longer. This varies by individual.
Can I restart Mounjaro if I regain weight?
Possibly, but this should be discussed with your prescriber. Restarting requires another clinical assessment and prescription. Some people benefit from a second course; others may need different support strategies. Your GP can assess whether restarting is appropriate for your situation.
What's the difference between stopping Mounjaro and Wegovy for weight regain?
Both Mounjaro (tirzepatide) and Wegovy (semaglutide) are weekly weight loss injections licensed in the UK. Weight regain patterns are similar — appetite returns within 1–2 weeks and regain depends on maintaining lifestyle changes. Mounjaro uses a dual GIP and GLP-1 mechanism, while Wegovy is a single GLP-1 agonist, but both require ongoing habit maintenance.
Should I see my GP before stopping Mounjaro?
Yes, always. Never stop prescription weight loss medication without medical guidance. Your GP can help you plan a safe discontinuation, discuss maintenance strategies, assess whether gradual dose reduction is appropriate, and provide ongoing support. They can also check whether continued treatment or alternative support might help you maintain your weight loss.
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.