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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5 Stone Weight Loss: UK Prescription Options & Results
Losing 5 stone (32kg) represents a significant health transformation that many UK adults achieve with structured support. Whether through NHS specialist services or private prescription options, prescription weight management medications—including Mounjaro and Wegovy—can support weight loss when combined with lifestyle changes. This guide covers your realistic options, eligibility criteria, and how to access evidence-based weight loss medication in the UK.
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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.
UK Prescription Weight Loss Medication Options
Three prescription-only medications are currently licensed for weight management in the UK: Mounjaro (tirzepatide), Wegovy (semaglutide), and Saxenda (liraglutide). These are GLP-1 and GIP/GLP-1 receptor agonist medications that work by reducing appetite, supporting fuller feelings after smaller meals, and slowing gastric emptying.
Clinical evidence shows meaningful results: Mounjaro users lost an average of 15–21% of their body weight in trials, whilst Wegovy supported average losses of around 15%. For a person weighing 100kg (15st 10lbs), these percentages could represent significant progress toward losing 5 stone. Individual results vary considerably and depend on dose, adherence, and lifestyle changes. All three medications require a prescription following clinical assessment by a GP or specialist prescriber, ensuring they are safe and appropriate for your personal health situation.
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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: How to Get Started
In the UK, you can access weight loss medication through two routes. The NHS funds tirzepatide (Mounjaro) through specialist tier 3 weight management services, but access varies significantly by region and waiting lists can be lengthy. Your GP can refer you to your local specialist service if you meet eligibility criteria: typically BMI of 30 or above, or 27 or above with weight-related health conditions such as type 2 diabetes or high blood pressure.
Privately, GPhC-registered online pharmacies offer prescription weight loss medication following a consultation with a UK-licensed prescriber—available without NHS referral. Use our free GLP-1 weight loss calculator to explore potential outcomes at different doses, and our BMI calculator to check your starting point. Speak with your GP about which route suits your circumstances.
- 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 lose 5 stone with prescription weight loss injections?
Achieving 5 stone loss is possible for many people, but individual results vary significantly. At typical maximum doses, Mounjaro and Wegovy support average losses of 15–21% body weight. For someone starting at 100kg (15st 10lbs), this could mean substantial progress. Success depends on the dose prescribed, your adherence, lifestyle changes, and personal factors. Your prescriber will set realistic goals based on your health.
Who is eligible for prescription weight loss medication on the NHS?
NHS eligibility typically requires a BMI of 30 or above, or 27–29.9 with weight-related health conditions like type 2 diabetes, high blood pressure, or cardiovascular disease. South Asian, Chinese, Black African, and Black Caribbean adults may have lower BMI thresholds. Referral comes through your GP to your local specialist tier 3 weight management service. Availability varies by region.
How quickly will I lose weight on these medications?
The NHS recommends sustainable weight loss of 0.5–1kg per week. Prescription medications may support faster initial losses in some people, but this varies. Most people reach their full effect over 16–20 weeks as doses increase. Weight loss continues whilst on the medication and your lifestyle supports it. Your prescriber will monitor progress and adjust dosing accordingly.
What's the difference between Mounjaro and Wegovy for weight loss?
Both are once-weekly injections for weight management in the UK. Mounjaro is a dual GIP/GLP-1 agonist (starting 2.5mg, maximum 15mg weekly), whilst Wegovy is a GLP-1 agonist only (starting 0.25mg, maximum 2.4mg weekly). Clinical trials show similar average weight loss results, around 15–21%. Your prescriber will assess which is more suitable based on your health history, other medications, and eligibility.
Can I get prescription weight loss medication privately if the NHS waiting list is long?
Yes. Private GPhC-registered online pharmacies offer Mounjaro and Wegovy following a clinical assessment with a UK-licensed prescriber. This route doesn't require NHS referral and is often faster than NHS waiting lists, though it involves private costs (typically £130–£300 monthly depending on dose). Your GP can still support your journey and monitor your health progress.
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.