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
Understanding Your Body and Healthy Weight in the UK
Your body composition — the balance of muscle, fat, bone, and water — plays a key role in your overall health. In the UK, healthcare professionals use several measures to assess body health, including BMI, waist circumference, and weight-to-height ratios. Understanding what constitutes a healthy weight for your height and age is the first step towards informed health decisions. The NHS provides clear guidance on healthy weight ranges, and our free BMI calculator can help you see where you stand quickly and accurately.
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 Guidance on Healthy Body Weight in the UK
The NHS classifies healthy weight using BMI (body mass index), calculated from your height and weight. For most UK adults, a BMI between 18.5 and 24.9 is considered healthy, though this varies by ethnicity. Adults of South Asian, Chinese, Black African, or Black Caribbean heritage face higher health risks at lower BMI levels, so the NHS recommends adjusted thresholds starting at BMI 23 instead of 25.
- Healthy weight (BMI 18.5–24.9): Associated with lower risk of weight-related health conditions
- Overweight (BMI 25–29.9): Increased risk of type 2 diabetes and heart disease
- Obese (BMI 30+): Significantly higher risk of serious health complications
Even a modest 5–10% reduction in body weight can improve blood pressure, blood sugar control, and joint health. Your GP can provide personalised advice on what a healthy weight means for you, taking account of your individual circumstances, fitness level, and medical history.
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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.
Body Composition and UK Health Resources
Body composition — the proportion of fat versus muscle — matters more than weight alone. Two people of the same weight can have very different health profiles depending on muscle mass. The weight converter on this page lets you easily switch between stone, pounds, and kilograms, making it simple to understand your weight in whichever units you prefer. Use our free BMI calculator above to check your personal BMI instantly, and explore NHS healthy weight guidance tailored to your height and age. For those considering weight management, the GLP-1 weight loss calculator can project potential outcomes with evidence-based medications.
- 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 considered a healthy weight in the UK?
The NHS defines healthy weight as a BMI between 18.5 and 24.9 for most adults. However, lower thresholds apply for people of South Asian, Chinese, Black African, or Black Caribbean heritage (18.5–22.9). Your GP can advise on what's healthy for your individual circumstances, taking account of muscle mass, age, and existing health conditions.
How do I calculate my BMI?
BMI is calculated as weight in kg divided by height in metres squared. Our free BMI calculator on this page does this instantly — simply enter your height and weight in your preferred units (stone, pounds, or kg) and get your result with NHS health context.
Does body weight tell you everything about health?
No. Weight is just one measure. Waist circumference, body composition, fitness level, and overall lifestyle matter too. Someone with high muscle mass might have a higher weight but be healthier than someone with lower muscle but the same BMI. That's why consulting your GP for personalised advice is important.
Is losing weight quickly safer than losing it slowly?
The NHS recommends losing weight at 0.5–1 kg (1–2 lbs) per week for sustainable results. Faster weight loss can lead to muscle loss and nutritional deficiencies. A calorie deficit of around 500 kcal per day typically results in safe, steady weight loss alongside regular physical activity.
What resources does the NHS provide for body weight management?
The NHS offers the NHS Weight Loss Plan, referral to specialist tier 3 weight management services in many areas, and guidance on healthy eating and physical activity. Your GP can discuss which support is right for you and may recommend referral to local services or prescription weight management options if appropriate.
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.