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
Can You Stay on Mounjaro Long Term?
Yes, you can stay on Mounjaro (tirzepatide) long term if it continues to work for you and your GP or prescriber agrees. There's currently no maximum time limit set by UK regulators, though most clinical data covers up to 72 weeks. Long-term use is increasingly common as people maintain weight loss with ongoing treatment. However, the decision to continue depends on your individual health, how well the medication is working, and whether benefits outweigh any side effects. Your prescriber will review this regularly with you.
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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.
Long-Term Use: Mounjaro vs Wegovy Comparison
Both Mounjaro (tirzepatide, a dual GIP and GLP-1 agonist) and Wegovy (semaglutide, a GLP-1 agonist only) are used long term in clinical practice, though formal licensed duration data differs. The SURMOUNT clinical trials for Mounjaro followed participants for up to 72 weeks, showing sustained weight loss when the medication was continued. Wegovy trials (STEP studies) similarly demonstrated weight maintenance over the study period. Neither medication has a maximum duration limit stated in UK guidance, meaning they can theoretically be continued indefinitely if clinically appropriate. The key difference is mechanism: Mounjaro's dual action may provide slightly different long-term effects than Wegovy's single GLP-1 pathway. Your prescriber will assess which suits your health needs through a clinical assessment and regular reviews. Individual response varies significantly — some people maintain results long term; others may need dose adjustments after months or years.
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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.
What Happens If You Stop Mounjaro?
If you stop taking Mounjaro, weight loss results typically plateau or reverse over time. Clinical evidence shows that stopping the medication often leads to weight regain within weeks to months, particularly if diet and lifestyle habits haven't permanently changed. This is why weight loss injections are considered long-term maintenance tools rather than short-term fixes. Some people successfully transition to self-management after losing weight on Mounjaro; others find they need to continue it. Your GP can help you decide whether to continue, adjust, or stop treatment based on your individual circumstances. Regular progress tracking can help you and your prescriber make informed decisions about ongoing use. Using our GLP-1 weight loss calculator can help you understand projected outcomes and discuss realistic expectations with your healthcare team.
- 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.
How long can you stay on Mounjaro safely?
There's no maximum time limit for Mounjaro use in the UK. Clinical trials followed people for up to 72 weeks with sustained benefit. Long-term use is recognised as safe when monitored by your prescriber through regular health reviews. Your GP or prescriber will assess you regularly to ensure it remains appropriate for your health.
Will Mounjaro work the same after years of use?
Some people maintain steady results; others find weight loss plateaus or they need dose adjustments over time. Your body may adapt, but your prescriber can modify treatment if needed. Regular monitoring with your GP helps identify if dose changes are necessary to maintain effectiveness.
Can you switch from Mounjaro to Wegovy long term?
Yes, switching between medications is possible, though it requires prescriber guidance. Mounjaro (dual GIP+GLP-1) and Wegovy (GLP-1 only) work slightly differently. A prescriber can assess whether switching is appropriate based on how you're responding, any side effects, or changing health needs. Approximate equivalences exist but aren't officially standardised.
What happens to your weight when you stop Mounjaro?
Most people regain weight after stopping, typically within weeks to months, unless diet and exercise habits have permanently changed. Weight loss injections work as ongoing maintenance tools. Discuss stopping plans with your GP — some people transition to self-management successfully; others benefit from continuing treatment long term.
Do you need breaks from Mounjaro or can you take it continuously?
Mounjaro is designed as a continuous, once-weekly injection with no mandated breaks. You continue the same dose schedule week after week. Your prescriber may occasionally suggest pausing for specific medical reasons, but routine breaks aren't standard practice. Always follow your prescriber's guidance about your individual treatment plan.
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.