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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Mounjaro Weight Gain: What Happens When You Stop
Some people experience weight regain after stopping Mounjaro, a widely-used weekly weight loss injection in the UK. This is often called weight rebound and is an important consideration before starting treatment. Understanding what causes weight regain, how to access Mounjaro through the NHS or privately, and what support is available can help you make an informed decision about whether this medication is right for you.
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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.
Understanding Weight Regain After Stopping Mounjaro
Weight regain after stopping Mounjaro (tirzepatide) is common because the medication works by suppressing appetite and improving how your body uses food. Once you stop the weekly weight loss injection, these effects gradually wear off over several weeks, and appetite typically returns to baseline levels. Clinical data shows that people who regain weight after stopping GLP-1 medications often return to their previous eating patterns without the appetite-suppressing effect of the drug.
- Appetite rebound: Hunger and food cravings return as the medication leaves your system
- Metabolic adjustment: Your body adapts back to pre-treatment metabolism
- Timeline: Weight regain typically begins 2–4 weeks after your last dose and can continue over months
- Prevention: Maintaining the dietary and lifestyle changes you made during treatment is crucial to preventing significant regain
The NHS recommends that weight loss medications work best when combined with sustained behaviour change. If you're considering stopping Mounjaro, your GP or prescriber can discuss strategies to maintain your weight loss long-term.
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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.
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NHS vs Private Mounjaro Access and Treatment Costs
Access to Mounjaro in the UK varies depending on whether you pursue NHS or private prescription routes. NHS access is through specialist tier 3 weight management services following a GP referral, though availability and waiting times differ significantly by region. Private access is available through online clinical assessments with UK-licensed prescribers, without needing NHS referral. Both routes require a clinical assessment to confirm you meet eligibility criteria—typically a BMI of 30 or above, or 27+ with weight-related health conditions. Before starting any weekly weight loss injection, use our free BMI calculator to understand your current health status, and discuss the cost, duration of treatment, and weight maintenance strategies 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.
Will I definitely regain weight when I stop Mounjaro?
Weight regain is common but not inevitable. Many people maintain significant weight loss if they continue the dietary and lifestyle changes they made during treatment. Your results depend on whether you sustain lower calorie intake and increased physical activity after stopping the medication. Your prescriber can discuss strategies to help you maintain your progress.
How quickly do you regain weight after stopping Mounjaro?
Weight regain typically begins 2–4 weeks after your final dose as appetite-suppressing effects wear off. The speed and amount of regain varies between individuals and depends largely on whether you maintain the eating and exercise habits you developed during treatment. Some people regain weight quickly; others maintain loss for months.
Can you restart Mounjaro if you regain weight?
Yes, you can restart Mounjaro if appropriate and clinically indicated. However, restarting requires a new clinical assessment with your GP or prescriber to ensure the medication remains suitable for you. Some people use Mounjaro cyclically or as needed, though long-term continuous use is the standard approach for sustained weight management.
What's the difference between Mounjaro and Wegovy for weight regain?
Both are weekly weight loss injections—Mounjaro (tirzepatide) is a dual GIP/GLP-1 agonist, while Wegovy (semaglutide) is a GLP-1 agonist only. Clinical trials suggest Mounjaro may produce slightly greater average weight loss, but individual results vary significantly. Weight regain patterns are similar for both medications after stopping.
How can I prevent weight regain after stopping Mounjaro?
Maintain the dietary habits and physical activity level you developed during treatment. This is the most important factor. Work with a dietitian or nutritionist if possible. Some people find our free progress tracker helpful for monitoring weight stability after stopping. Your GP can also refer you to weight management support services available in your area.
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.