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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Best Weight Loss Gym Program in the UK
Finding the best weight loss gym program involves more than just exercise — it's about combining physical activity with evidence-based approaches to weight management. For eligible UK adults, prescription weight loss medication can significantly enhance results when used alongside gym training and dietary changes. This guide explains the prescription weight management options available through the NHS and privately, helping you understand whether medication might support your fitness journey.
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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.
Prescription Weight Loss Options in the UK
Three prescription medications are currently licensed in the UK for weight management:
- Mounjaro (tirzepatide) — a once-weekly injection that works as a dual GIP and GLP-1 receptor agonist. Clinical trials showed participants lost an average of 15–21% of their body weight over 72 weeks alongside diet and exercise.
- Wegovy (semaglutide) — a once-weekly GLP-1 injection. Evidence from clinical trials demonstrated average weight loss of approximately 15% body weight when combined with lifestyle changes.
- Saxenda (liraglutide) — a daily GLP-1 injection, though less commonly prescribed than the once-weekly options.
All three are prescription-only medicines requiring clinical assessment. Eligibility typically includes adults with a BMI of 30 or above, or 27 or above with weight-related health conditions. Individual results vary significantly, and medication works best when combined with gym training and dietary modifications, not as a standalone solution.
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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.
NHS vs Private Access and Getting Started
NHS access: Mounjaro and Wegovy are available through NHS specialist tier 3 weight management services. Your GP can refer you, though waiting times vary significantly by region and availability can be limited in some areas.
Private access: Both medications are available through online prescribing services following a clinical assessment from a UK-licensed prescriber. This route typically offers faster access without NHS referral requirements.
Before exploring prescription options, calculate your BMI using our free BMI calculator to understand where you currently stand. Combined with our GLP-1 weight loss calculator, you can explore projected outcomes at different medication doses. Discuss these options with your GP to determine whether prescription weight loss treatment is appropriate for your individual circumstances and fitness goals.
- 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.
Can I use prescription weight loss medication while doing gym training?
Yes. Prescription weight loss medications like Mounjaro and Wegovy are designed to be used alongside lifestyle changes, including exercise. In fact, clinical trials combined medication with diet and physical activity. Always inform your prescriber about your gym routine, and ensure adequate calorie and protein intake to support muscle maintenance during training.
How much weight can I realistically lose with medication and a gym program?
Results vary between individuals. Clinical trials showed average weight loss of 15–21% body weight with Mounjaro and approximately 15% with Wegovy over several months. Your personal results depend on medication dose, adherence, diet, gym consistency, and individual metabolism. Use our weight loss calculator to explore potential outcomes.
What is the difference between Mounjaro and Wegovy?
Both are once-weekly injections, but Mounjaro (tirzepatide) is a dual GIP and GLP-1 agonist, while Wegovy (semaglutide) is a GLP-1-only medication. Clinical data suggests slightly higher average weight loss with Mounjaro, though individual response varies. Your prescriber will recommend which is most suitable for you.
How do I find out if I'm eligible for prescription weight loss medication on the NHS?
Start by speaking with your GP. Use our free BMI calculator to determine your BMI, then discuss with your GP whether you meet eligibility criteria (typically BMI 30+ or 27+ with weight-related conditions). Your GP can refer you to a specialist weight management service if appropriate.
Can I combine weight loss medication with my own gym routine, or do I need a specific program?
You can combine medication with your own training. However, many people find structured gym programs helpful for consistency and proper technique. Any gym program works — the key is combining it with medication (if eligible), consistent calorie deficit, adequate protein, and adherence. Track your progress using our free progress tracker.
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.