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
Gaining Weight After Mounjaro — Why It Happens and What to Do
Some people regain weight after stopping Mounjaro, or experience slower progress during treatment. This is normal and doesn't mean the medication has failed — it reflects how GLP-1 medications work and your individual health context. Understanding why weight regain happens, plus your UK options for continuing treatment or adjusting your approach, helps you make informed decisions about next steps. Our GLP-1 weight loss calculator can help estimate your progress with different doses, whilst our BMI calculator shows where your current weight sits against NHS guidelines.
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.
Why Weight Regain Happens After Mounjaro
Weight regain after stopping Mounjaro is not uncommon and happens for several reasons. GLP-1 medications like Mounjaro work by reducing appetite and supporting fullness — when you stop taking them, these hormonal effects gradually fade, and natural appetite signals return. This doesn't mean the medication "failed" — it's how the medication is designed to work.
Additionally, if lifestyle changes (diet and physical activity) weren't established during treatment, weight can return quickly. Mounjaro is most effective when used alongside a reduced-calorie diet and increased physical activity. Some people also experience slower weight loss during treatment due to reaching a plateau, dose adjustment timing, or individual metabolic factors. During treatment, your prescriber can assess whether increasing your dose (up to the maximum 15 mg weekly) or adjusting your approach might help. Rebound weight gain is not failure — it's a signal to discuss ongoing support with your GP or prescriber.
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.
UK Costs and Access Options for Continuing Mounjaro
NHS access: If you're on Mounjaro through an NHS tier 3 specialist weight management service, you can discuss weight regain with your prescriber. They may adjust your dose, offer additional lifestyle support, or continue the medication long-term. NHS access varies significantly by region and waiting lists can be lengthy.
Private access: A UK-licensed prescriber can assess you for continued or restarted treatment via online consultation (typically £20–£50). Mounjaro costs approximately £140–£250 monthly depending on your dose — the 5 mg maintenance dose is usually less expensive than higher doses. You'll need to maintain regular check-ins with your prescriber (typically every 3–6 months). Switching to a weekly weight loss injection like Wegovy may also be an option to discuss with a prescriber, depending on your individual circumstances and response.
- 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 it normal to regain weight after stopping Mounjaro?
Yes, weight regain is common after stopping GLP-1 medications because appetite-suppressing effects wear off. This doesn't mean the medication failed. Maintaining the lifestyle changes (diet and activity) established during treatment helps minimise regain. Many people continue Mounjaro long-term or switch to another weekly weight loss injection to sustain results.
Can I restart Mounjaro if I stopped and regained weight?
Yes, you can restart Mounjaro if clinically appropriate. A UK-licensed prescriber can assess your situation via online consultation. You'll typically restart at the 2.5 mg dose and titrate up over weeks. If you're accessing Mounjaro privately, costs and prescriber fees apply each time you restart treatment.
What does Mounjaro cost on the NHS vs privately in the UK?
Mounjaro is free on the NHS if prescribed through a specialist tier 3 weight management service, but availability and waiting times vary by region. Privately, expect £140–£250 monthly for the medication plus £20–£50 for an online consultation and ongoing prescriber fees (usually every 3–6 months). Costs depend on your dose.
What's the difference between Mounjaro and Wegovy for weight regain?
Mounjaro (tirzepatide) is a dual GIP/GLP-1 agonist; Wegovy (semaglutide) is a GLP-1-only agonist. Clinical trials show Mounjaro may produce slightly greater average weight loss, but individual results vary. Both require a prescription and clinical assessment. A prescriber can discuss which is more appropriate for your circumstances.
How often do I need to see a prescriber if I continue Mounjaro privately?
UK prescribers typically require check-ins every 3–6 months when you're taking Mounjaro privately. This includes an online consultation (usually £20–£50) to assess your progress, discuss side effects, and authorise repeat prescriptions. Some providers offer bundled packages covering medication and regular reviews.
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.