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
Is Watermelon A Good Weight Loss Food?
Watermelon can support weight loss as part of a balanced diet due to its high water content and low calorie density — about 30 calories per 100g. However, weight loss ultimately depends on overall calorie intake and lifestyle changes. For adults in the UK who need additional support, prescription weight management options are available through the NHS or private prescribers. Our free BMI calculator can help you understand where you stand, and if you're eligible, a GP can discuss weight loss strategies tailored to your needs.
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 Prescription Weight Loss Options
If you're looking for weight management support beyond dietary changes, several prescription weight loss medications are available in the UK for eligible adults. These include Mounjaro (tirzepatide), a dual GIP and GLP-1 receptor agonist, and Wegovy (semaglutide), a GLP-1 agonist. Both are once-weekly injections licensed for weight management in adults with a BMI of 30 or above, or BMI 27–29.9 with weight-related health conditions.
Clinical trials showed that Mounjaro helped participants lose an average of 15–21% of body weight, whilst Wegovy achieved approximately 15% average weight loss — though individual results vary. These medications work alongside a reduced-calorie diet and increased physical activity, not as a replacement for lifestyle changes. Eligibility is assessed individually by a prescriber following a 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 in the UK
NHS access to prescription weight loss medication is through specialist tier 3 weight management services, typically requiring a GP referral. Availability varies significantly by region, and waiting lists can be lengthy in many areas. Private access is available through GPhC-registered online prescribers without an NHS referral — a licensed prescriber assesses your eligibility following an online consultation.
Regardless of route, prescription weight loss medicines are prescription-only and require clinical assessment. Speak to your GP about your weight management options, or explore private prescribing if you're eligible. Use our GLP-1 weight loss calculator to see estimated outcomes at different doses, and our weight converter to track progress in stone and lbs.
- 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 watermelon alone help me lose weight?
Watermelon is low in calories and high in water, making it nutritious, but weight loss requires a calorie deficit. Eating watermelon as part of a balanced, calorie-controlled diet can help, but it's not a standalone solution. For significant, sustained weight loss, lifestyle changes combined with professional support are more effective.
What's my BMI and how does it relate to weight loss?
Your BMI indicates whether your weight is in a healthy range according to NHS guidelines (18.5–24.9 for most adults; 18.5–22.9 for South Asian, Chinese, Black African, or Black Caribbean adults). Use our free BMI calculator to check yours. Your BMI helps determine eligibility for prescription weight loss medication.
Am I eligible for prescription weight loss medication in the UK?
You may be eligible if you have a BMI of 30 or above, or 27–29.9 with weight-related health conditions like type 2 diabetes or high blood pressure. A GP or licensed prescriber assesses eligibility individually. Contact your GP to discuss options, or explore private prescribing with a GPhC-registered provider.
What's the difference between Mounjaro and Wegovy?
Both are once-weekly injections licensed for weight management in the UK. Mounjaro (tirzepatide) is a dual GIP and GLP-1 agonist with average weight loss of 15–21%; Wegovy (semaglutide) is a GLP-1 agonist with average weight loss around 15%. Effectiveness varies individually. A prescriber will advise which is suitable for you.
How do I find out if prescription weight loss is right for me?
Speak to your GP, who can assess your health history, BMI, and any weight-related conditions. If NHS waiting times are long in your area, private online prescribers can provide assessment without referral. Either route requires a clinical assessment to confirm prescription suitability and monitor safety. ```
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.