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
What Is a Healthy BMI Range According to NHS Guidance?
A healthy BMI range in the UK is between 18.5 and 24.9, according to NHS guidelines. This range applies to most adults and is based on extensive research into health outcomes. Your BMI (body mass index) is calculated using a simple formula: your weight in kilograms divided by your height in metres squared. Understanding your personal BMI range and where you fall within it is an important first step in managing your weight and overall health. Use our free BMI calculator above to find your personal BMI instantly, and then refer to the guidance below to understand what it means for you.
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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 BMI Categories and What They Mean
The NHS recognises five BMI categories for adults, each with different health implications. A BMI below 18.5 is classified as underweight, which can indicate insufficient nutrition or underlying health concerns. The healthy BMI range of 18.5–24.9 is where health risks from weight are lowest. A BMI of 25–29.9 puts you in the overweight category, which increases risk of type 2 diabetes and heart disease. The obese category starts at BMI 30, subdivided into Class I (30–34.9), Class II (35–39.9), and Class III or severely obese (40 and above).
It's important to note that the BMI formula UK uses has limitations — it does not distinguish between muscle mass and fat, so athletes or very muscular individuals may have a high BMI despite low body fat. Additionally, if you are of South Asian, Chinese, Black African, or Black Caribbean heritage, the NHS recommends slightly lower thresholds. For these groups, a healthy BMI range is 18.5–22.9, and the overweight threshold begins at BMI 23, because these populations face higher cardiovascular and diabetes risk at lower BMI levels.
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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.
When to Seek Help and What the NHS Offers
If your BMI is in the overweight or obese range, your GP can offer support and guidance. The NHS provides a weight management pathway with multiple tiers of support. Tier 1 includes digital tools, self-help resources, and community weight management programmes — you can access these without a referral. Tier 2 involves primary care interventions and behaviour change support through your GP. Tier 3 and 4 are specialist multidisciplinary weight management services, where medications or bariatric surgery may be considered for eligible individuals. Access varies by region. Start by discussing your BMI and health with your GP, who can assess your individual circumstances and signpost you to appropriate support.
- 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 overweight and obese according to NHS BMI categories?
Overweight is a BMI of 25–29.9, while obesity starts at BMI 30. Both increase health risks, but obesity carries significantly higher risk of type 2 diabetes, heart disease, and certain cancers. Your GP can advise on management for either category.
I'm of South Asian heritage — does the healthy BMI range apply to me?
No. The NHS recommends lower BMI thresholds for South Asian, Chinese, Black African, and Black Caribbean adults due to higher disease risk at lower BMI levels. For these groups, a healthy BMI is 18.5–22.9, and overweight begins at 23. Discuss your personal threshold with your GP.
I have a high BMI but I'm very muscular — is BMI accurate for me?
BMI has limitations for muscular individuals because it doesn't distinguish between muscle and fat. If you're very athletic or have significant muscle mass, your GP may use additional measures like waist circumference or body composition analysis to assess your health more accurately.
How can I calculate my personal BMI range using the NHS formula?
Use our free BMI calculator above — simply enter your height and weight, and it will show your BMI instantly. The formula is: weight (kg) ÷ height (m)². You can also use our weight converter to switch between stone and kilograms if needed.
What should I do if my BMI is in the healthy range but I'm still concerned about my weight?
Even within a healthy BMI range, other factors matter — waist circumference, fitness level, and overall health. If you have health concerns, speak to your GP. They can assess your individual situation and recommend appropriate lifestyle changes or further investigation if needed.
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.