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 Weight and BMI — A UK Health Guide
Weight management is one of the most important aspects of health in the UK today. Whether you're looking to understand your current weight, check if it's in a healthy range, or plan your health journey, having accurate information aligned with NHS guidance is essential. This guide covers everything UK adults need to know about weight, BMI, and healthy weight ranges using UK measurements like stone, pounds, and kilograms.
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 Weight Categories and Healthy Ranges
The NHS defines healthy weight using BMI (Body Mass Index) categories, which apply to all UK adults aged 18 and over. A healthy BMI falls between 18.5 and 24.9 kg/m². However, for adults of South Asian, Chinese, Black African, or Black Caribbean heritage, the NHS recommends lower thresholds due to higher health risks at the same BMI levels.
- Healthy weight: BMI 18.5–24.9
- Overweight: BMI 25.0–29.9
- Obese (Class I): BMI 30.0–34.9
- Obese (Class II): BMI 35.0–39.9
- Severely obese: BMI 40.0 and above
Use our free BMI calculator above to find your personal BMI instantly and see where you fall within these NHS categories. Remember that BMI is a screening tool — it doesn't account for muscle mass or where fat is distributed on your body.
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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.
UK Tools and Resources for Weight Management
MyWeightCheck provides several free tools to support your UK health guidance journey. Our weight converter helps you switch between kilograms, stone, and pounds — essential for understanding weight across different contexts. Our GLP-1 weight loss calculator is available for those interested in understanding weight loss medication options like Mounjaro or Wegovy, which are now available through NHS specialist services and private prescribing in the UK.
If you're tracking progress over time, our free progress tracker lets you log weight changes and visualise your health journey. Your GP can also provide personalised guidance about what a healthy weight means for your individual health, medical history, and risk factors.
- 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 a healthy weight range for an adult in the UK?
A healthy weight depends on your height and is expressed as a BMI between 18.5 and 24.9. For example, a 5ft 8in (173cm) adult should weigh between approximately 55–75 kg (8st 10lbs–11st 10lbs). Use our free BMI calculator to find your healthy range based on your height.
Why do South Asian, Black African, and Caribbean adults have different NHS weight thresholds?
The NHS recommends lower BMI thresholds for these ethnic groups because research shows they develop weight-related health complications like type 2 diabetes and heart disease at lower BMI levels than other populations. This reflects genuine biological differences in how these groups respond to excess weight.
How much weight should I aim to lose per week safely?
The NHS recommends a safe weight loss rate of 0.5–1 kg per week. This typically requires a calorie deficit of about 500 kcal per day and should be combined with sustainable dietary changes and increased physical activity. Faster weight loss can result in muscle loss and is not recommended without medical supervision.
What is the difference between overweight and obese according to NHS guidelines?
Overweight is a BMI of 25.0–29.9, while obese begins at BMI 30.0. Both categories increase health risks, but obesity carries higher risks for conditions like type 2 diabetes, cardiovascular disease, and certain cancers. Your GP can assess your individual risk based on other factors like waist circumference and medical history.
Are there prescription weight loss medications available on the NHS in the UK?
Yes. Medications like Mounjaro (tirzepatide) and Wegovy (semaglutide) are now available through NHS specialist weight management services for eligible adults. Eligibility typically requires a BMI of 30 or above, or 27+ with weight-related health conditions. Access varies by region — your GP can refer you to specialist services 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.