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
Slimming Body — Evidence-Based UK Health Guidance
Slimming your body safely means understanding sustainable weight loss, not pursuing quick fixes. The NHS recommends losing weight at a rate of 0.5 to 1 kg per week for long-term success. This approach protects muscle mass and supports lasting habit change. Whether through dietary adjustments, increased physical activity, or prescription support, sustainable slimming involves making changes you can maintain. UK health information emphasises that even a 5 to 10 percent reduction in body weight can bring meaningful health benefits, including lower blood pressure, improved blood sugar control, and reduced joint strain.
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.
How to Slim Your Body Sustainably
Sustainable weight management requires a combination of realistic goals, lifestyle changes, and support. Use our free BMI calculator to understand your current weight status and establish a baseline for tracking progress.
- Calorie deficit: Losing approximately 0.5 kg per week typically requires a daily deficit of around 500 kcal. This can be achieved through dietary changes, increased activity, or both.
- Balanced nutrition: Focus on whole foods, adequate protein, vegetables, and fibre to support satiety and sustainable eating patterns.
- Regular physical activity: Aim for at least 150 minutes of moderate activity weekly, plus strength training. This protects muscle mass during weight loss.
- Behavioural support: The NHS offers free tier 1 and tier 2 weight management programmes in most areas. Your GP can signpost you to local services.
- Prescription support: For those with a BMI of 30 or above, or 27 or above with weight-related health conditions, prescription weight loss medications may be available through specialist NHS services or private 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.
Weight Loss Medications and Medical Support
Prescription-only GLP-1 medications like Wegovy (semaglutide) may help some adults achieve slimming when used alongside lifestyle changes. Clinical trials show Wegovy helps participants lose an average of approximately 15 percent of body weight — though individual results vary significantly.
Access in the UK is through NHS specialist tier 3 weight management services or private online prescribers following clinical assessment. Our GLP-1 weight loss calculator can help you estimate potential outcomes at different doses. Always consult your GP about whether prescription support is suitable for your situation. Medical support may also include assessment for underlying conditions affecting weight, such as thyroid problems or polycystic ovary syndrome.
- 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.
What is the safest rate to slim your body?
The NHS recommends losing 0.5 to 1 kg per week for sustainable, healthy weight loss. Faster loss increases the risk of muscle loss, nutritional deficiency, and regaining weight. Your GP can advise on a safe rate for your individual circumstances.
Can I slim my body without dieting?
Weight loss typically requires a calorie deficit, which usually involves some dietary change. However, you don't need to follow a strict "diet" — sustainable slimming often works better through gradual habit changes, increased activity, and eating more satisfying, whole foods rather than restriction.
How long does it take to see slimming results?
You may notice changes in how clothes fit within 2 to 3 weeks, though scale changes vary. Most people see meaningful physical changes within 8 to 12 weeks of consistent effort. Progress isn't always linear — use our free progress tracker to log both scale weight and other metrics like how you feel and energy levels.
Are slimming injections available on the NHS in the UK?
Prescription weight loss injections like Wegovy are available through NHS specialist tier 3 weight management services, though availability and waiting times vary significantly by region. Your GP can refer you to your local service. They are also available privately through registered online prescribers following clinical assessment.
What should I do if slimming isn't working?
If weight loss stalls, review your calorie intake, activity levels, and sleep quality. Some people plateau naturally. Medical factors like thyroid disorders, hormonal changes, or certain medications can affect weight loss. Your GP can investigate and may suggest specialist support or medication options suited to your health profile.
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.