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
4 Stone Weight Loss — Prescription Medication Options in the UK
Losing 4 stone (56 lbs or approximately 25 kg) is a significant health goal that many UK adults pursue to improve their wellbeing. Prescription weight management medication can support this journey when combined with dietary changes and increased physical activity. This guide explains UK-licensed options available through both NHS and private prescribing, eligibility criteria, and what realistic outcomes look like. Use our free BMI calculator to understand where you are now, and explore how prescription options might fit into your weight loss plan.
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.
UK-Licensed Prescription Weight Loss Options
Three prescription medications are licensed in the UK for weight management:
- Mounjaro (tirzepatide) — dual GIP and GLP-1 receptor agonist, once-weekly injection, doses 2.5 mg to 15 mg. Clinical trials showed average weight loss of 15–21% body weight.
- Wegovy (semaglutide) — GLP-1 receptor agonist, once-weekly injection, doses 0.25 mg to 2.4 mg. Average weight loss approximately 15% body weight in trials.
- Saxenda (liraglutide) — GLP-1 receptor agonist, daily injection, doses 0.6 mg to 3 mg. Established option with strong evidence base.
Eligibility requires a BMI of 30 or above, or BMI 27–29.9 with weight-related health conditions (type 2 diabetes, high blood pressure, heart disease, or sleep apnoea). For adults of South Asian, Chinese, Black African, or Black Caribbean heritage, lower BMI thresholds apply. All require a prescription following clinical assessment.
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.
NHS vs Private Access — How to Get Started
NHS access: Referral to a specialist tier 3 weight management service through your GP. Availability and waiting times vary significantly by region. Many areas have lengthy waiting lists. Your GP can assess whether you meet local criteria.
Private access: Online consultation with a UK-licensed prescriber, prescription issued if clinically appropriate, dispensed by a registered pharmacy. Available without NHS referral. Costs vary by dose and provider (typically £129–£320 monthly).
Start by speaking with your GP about your weight loss goals. They can discuss both NHS options and your eligibility, or provide guidance on private prescribing. Try our free weight loss calculator to see estimated outcomes at different medication doses.
What 4 stone weight loss means: At an average weight loss rate of 0.5–1 kg per week (NHS guidance), losing 4 stone would take approximately 24–49 weeks with medication and lifestyle support. Individual results vary significantly based on starting weight, dose, diet adherence, and physical activity. Clinical evidence shows that prescription medication works best alongside a reduced-calorie diet and increased exercise.
Use our progress tracker to log your weight, monitor trends, and celebrate milestones as you progress. Remember that prescription weight loss medication is a tool — sustainable results depend on ongoing lifestyle changes including dietary choices and physical activity, which your prescriber and GP can support.
- 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 much weight can I realistically lose with prescription medication?
Clinical trials show average weight loss of 15–21% body weight with Mounjaro and approximately 15% with Wegovy. For someone starting at, say, 120 kg, 15% loss equals 18 kg (2.8 stone). Individual results vary considerably. Medication works best alongside a reduced-calorie diet and increased physical activity. Your prescriber can discuss realistic outcomes for your situation.
Am I eligible for NHS weight loss medication?
You may be eligible if you have a BMI of 30 or above, or BMI 27–29.9 with weight-related health conditions (type 2 diabetes, high blood pressure, heart disease, sleep apnoea). South Asian, Chinese, Black African, or Black Caribbean adults may be eligible at lower BMI thresholds. Your GP can assess your eligibility and discuss referral to specialist weight management services in your area.
What's the difference between Mounjaro and Wegovy?
Mounjaro (tirzepatide) is a dual GIP and GLP-1 agonist with maximum dose 15 mg weekly. Wegovy (semaglutide) is a single GLP-1 agonist with maximum dose 2.4 mg weekly. Both are once-weekly injections. Clinical trial data shows Mounjaro may provide slightly greater average weight loss, but both are effective. Your prescriber will recommend the best option for your individual health needs.
How long does it take to see results?
Most people notice appetite changes within the first few weeks. Visible weight loss typically becomes apparent after 4–8 weeks of consistent use alongside dietary changes. Doses are gradually increased over weeks, so maximum benefit builds over time. Patience is important — sustainable weight loss takes months, not weeks.
Can I use MyWeightCheck tools to track my progress?
Yes. Use our free BMI calculator to check your starting point and monitor improvements as your weight changes. Our weight loss calculator shows projected outcomes at different medication doses. Our progress tracker lets you log weekly weights, track your journey toward 4 stone loss, and see your progress visualised over time.
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.