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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How to Figure Out Your Weight Loss Percentage
Working out your weight loss percentage helps you track progress accurately and celebrate real achievements in your weight management journey. Weight loss percentage is calculated by dividing the amount of weight lost by your starting weight, then multiplying by 100. For UK adults managing their weight, understanding this metric — alongside your BMI — can be motivating and informative. Whether you're losing weight through lifestyle changes alone or exploring prescription options available through the NHS and private clinics, knowing your percentage progress gives you a clear picture of your health improvements.
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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 Management Options in the UK
Three prescription medications are currently licensed in the UK for weight loss and weight management:
- Mounjaro (tirzepatide) — a dual GIP and GLP-1 receptor agonist. Clinical trials showed average weight loss of around 15–21% of body weight over 72 weeks, though individual results vary significantly.
- Wegovy (semaglutide) — a GLP-1 receptor agonist available as once-weekly injections. Clinical evidence demonstrated average weight loss of approximately 15% of body weight in trials, alongside a reduced-calorie diet and increased physical activity.
- Saxenda (liraglutide) — a daily GLP-1 injection. Evidence supports modest but sustained weight loss across clinical studies.
All three are prescription-only medicines requiring clinical assessment. You may be eligible if you have a BMI of 30 or above, or 27 or above with weight-related health conditions such as type 2 diabetes, high blood pressure, or cardiovascular disease. Use our GLP-1 weight loss calculator above to explore potential weight loss at different doses, and our BMI calculator to assess your starting point.
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 in the UK
NHS access to weight loss medication is available through specialist tier 3 weight management services, typically requiring a GP referral. However, NHS availability varies significantly by region, and waiting lists can be lengthy in many areas. Regional NHS integrated care boards (ICBs) control access and eligibility criteria.
Private access is available through GPhC-registered online clinics following a clinical assessment by a UK-licensed prescriber. This route does not require NHS referral and medication can be dispensed within days. Costs vary by dose and provider, typically ranging from £129 to £320 per month.
If you're interested in prescription weight loss medication, have a conversation with your GP first. They can assess your eligibility, discuss your health history, and either refer you to NHS specialist services or advise you about private options. Your GP can also help monitor your progress and manage any side effects.
- 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 do I calculate my weight loss percentage?
Divide the amount of weight lost by your starting weight, then multiply by 100. For example, if you started at 100kg and lost 15kg, your percentage loss is (15 ÷ 100) × 100 = 15%. Use our progress tracker to log your weight and automatically calculate your percentage progress over time.
What percentage weight loss is considered healthy?
The NHS recommends losing weight at a rate of 0.5–1kg per week for sustainable results. Even a 5–10% reduction in body weight can have meaningful health benefits, including improved blood pressure, better blood sugar control, and reduced joint strain. Aim for gradual, consistent progress rather than rapid loss.
Can prescription weight loss medications help me achieve a specific weight loss percentage?
Clinical trials showed average weight loss percentages of 15–21% with Mounjaro and around 15% with Wegovy, but individual results vary significantly based on your starting weight, lifestyle changes, adherence, and genetics. A prescriber will assess whether weight loss medication is suitable for you and monitor your progress. Our GLP-1 weight loss calculator can help you explore projected outcomes at different doses.
Am I eligible for prescription weight loss medication on the NHS?
You may be eligible if you have a BMI of 30 or above, or 27 or above with weight-related health conditions. Access is through specialist NHS weight management services, typically via GP referral. Your GP can assess your individual eligibility and discuss whether referral or private options are appropriate for your situation.
What should I do first if I want to explore weight loss options?
Start by calculating your current BMI using our free BMI calculator on this page — this helps establish your starting point. Then have a conversation with your GP about your weight management goals. They can assess your eligibility for prescription medication, discuss lifestyle changes, and advise whether NHS specialist referral or private options suit your needs and circumstances.
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.