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
How Can I Be Skinny — A UK Health Perspective
Being "skinny" often means reaching a healthy weight for your height and body type. The NHS defines healthy weight through BMI (body mass index), and the good news is that sustainable weight loss is achievable for most people through evidence-based methods. This UK health guide covers practical, realistic approaches to weight management — not extreme dieting, but lasting lifestyle changes backed by NHS guidance and clinical research.
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.
NHS-Approved Approaches to Healthy Weight
The NHS recommends losing weight at a sustainable rate of 0.5 to 1 kg per week, which typically requires a calorie deficit of around 500 kcal per day. A reduced-calorie diet combined with increased physical activity is the foundation of successful weight loss — not restriction or deprivation.
- Balanced diet: Focus on whole foods, lean proteins, vegetables, and wholegrains rather than fad diets
- Physical activity: Aim for at least 150 minutes of moderate exercise per week (walking, cycling, swimming)
- Realistic targets: A healthy BMI in the UK is 18.5 to 24.9 — work with your GP to set achievable goals
- Behavioural support: NHS weight management programmes and apps help track progress and maintain motivation
For South Asian, Chinese, Black African, or Black Caribbean adults, slightly lower BMI thresholds apply due to higher health risk at the same weight. Calculate your personal healthy weight range using our free BMI calculator above to understand your specific target.
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.
When Professional Support Helps
If you've tried lifestyle changes without success, or if you have a BMI of 30 or above (or 27+ with weight-related health conditions like type 2 diabetes or high blood pressure), your GP can refer you to NHS tier 3 weight management services. These specialist services may offer structured weight loss programmes, behavioural therapy, and in some cases, prescription weight loss medications such as GLP-1 injections.
Our free GLP-1 weight loss calculator can help you understand potential weight loss with medical support, and the progress tracker lets you monitor your journey. Remember, sustainable weight loss combines multiple approaches — medication, diet, exercise, and psychological support all work together for best results.
- 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's the difference between "skinny" and "healthy weight"?
"Skinny" often suggests very low weight, but healthy weight is what's right for your height, age, and body composition. NHS-defined healthy weight (BMI 18.5–24.9) supports better health outcomes than being significantly underweight. Calculate your healthy range using the BMI calculator above.
How long does it take to reach a healthy weight?
At the NHS-recommended pace of 0.5–1 kg per week, timeframe depends on your starting weight. For example, losing 10 kg takes roughly 10–20 weeks. Slower loss is more sustainable and helps preserve muscle mass — avoid very gradual weight management without medical supervision.
Can I lose weight without exercise?
Weight loss is primarily driven by calorie intake, so diet change alone can work. However, the NHS recommends combining diet with physical activity for better health outcomes, improved cardiovascular fitness, and reduced risk of weight regain. Exercise also supports mental wellbeing.
What if I have a medical condition affecting my weight?
Conditions like thyroid disease, PCOS, and depression can make weight loss harder. Your GP can investigate underlying causes, adjust medications if needed, and refer you to specialist services. Never assume weight loss is simply about willpower — medical factors often play a significant role.
Are weight loss injections available on the NHS in the UK?
Yes — GLP-1 medications like Mounjaro and Wegovy are now approved for NHS specialist weight management services. Access is typically through tier 3 services after GP referral. Private access is also available through registered online prescribers following clinical assessment. Availability varies by region.
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.