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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1 Stone Weight Loss Before and After: What's Realistic with UK Medication
Losing 1 stone (6.4kg) is a meaningful health milestone that many UK adults aim for. If you're considering prescription weight management options like Mounjaro or Wegovy, understanding what realistic results look like — and how to achieve them — is essential. This guide covers the prescription weight loss medications available through the NHS and privately, who is eligible, and what the clinical evidence actually shows about weight loss at this level. Remember that individual results vary significantly, and medication works best alongside lifestyle changes like improved diet and increased physical activity.
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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-Licensed Prescription Weight Loss Options
Three prescription medications are licensed for weight management in the UK: Mounjaro (tirzepatide), Wegovy (semaglutide), and Saxenda (liraglutide). Losing 1 stone represents roughly 7–10% of body weight for many UK adults — a loss that clinical trials show is achievable within the first 3–4 months of treatment at maintenance doses.
Mounjaro clinical trials showed participants lost an average of 15–21% of their body weight, meaning 1 stone would be an early milestone for many users. Wegovy showed average weight losses of around 15%, also making 1 stone a realistic early target. Both are GLP-1 receptor agonist medications (Mounjaro is dual GIP+GLP-1) that reduce appetite and support feeling fuller after smaller meals.
- Mounjaro: once-weekly injection, doses from 2.5mg to 15mg
- Wegovy: once-weekly injection, doses from 0.25mg to 2.4mg
- Saxenda: once-daily injection, doses from 0.6mg to 3mg
All require a prescription following a clinical assessment. Eligibility is assessed on an individual basis by a prescriber or specialist service.
Clinically BackedWeight Loss
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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.
Accessing Weight Loss Medication in the UK: NHS vs Private
In the NHS, weight loss medications are accessed through specialist tier 3/4 weight management services — not standard GP prescription. Your GP can refer you, but availability varies significantly by region. Waiting times can be months or even years in many areas. Privately, GLP-1 medications are available through UK-licensed online prescribers following a clinical consultation. Private costs typically range from £120–£300 per month depending on the dose.
To find out if you're eligible, check your BMI using our free BMI calculator above. Adults with a BMI of 30 or above, or 27–29 with weight-related health conditions like type 2 diabetes or high blood pressure, may qualify. Your GP can discuss NHS options, or you can explore private prescribing independently. Either way, a qualified prescriber will assess whether medication is suitable for your individual health profile.
- 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 1 stone (6.4kg) a realistic weight loss goal with prescription medication?
Yes. Clinical trials show most users lose 5–15% of their body weight in the first 3–4 months, meaning 1 stone is an achievable early milestone. However, results vary between individuals. Weight loss depends on the dose, how long you've been taking the medication, lifestyle changes, and personal metabolism. Your GP or prescriber can give you a more personalised estimate.
How long does it take to lose 1 stone with Mounjaro or Wegovy?
Most users see meaningful weight loss between weeks 8–12 once they reach a maintenance dose. Losing 1 stone could take 8–16 weeks depending on your starting weight, the dose, and how your body responds. Doses are increased gradually (every 4 weeks), so full effects take time. Sustainable weight loss is better than rapid loss.
What happens after I lose 1 stone — do I keep taking the medication?
GLP-1 medications are typically long-term treatments. If you stop taking them, weight often returns because the underlying appetite regulation changes reverse. Your prescriber will discuss ongoing use with you based on your goals and how well the medication is working. Some people continue at maintenance doses; others adjust based on progress.
Can I use the NHS weight loss calculator to estimate my potential weight loss?
Yes. Our free GLP-1 weight loss calculator above can help you project potential weight loss at different doses and timeframes. It gives you a rough idea based on clinical trial data — but remember, individual results vary. Use it alongside a conversation with your GP or prescriber for a more personalised picture.
What's the difference between seeing results "before and after" in studies vs real life?
Clinical trial participants follow strict protocols including reduced-calorie diets and increased exercise. Real-world results are usually smaller unless you also make lifestyle changes. Medication works best as part of a broader approach — diet, activity, and behaviour change matter as much as the injection itself. Track your progress with our free progress tracker to see your personal results.
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.