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 The Normal Range Of BMI According To NHS Guidelines?
The normal healthy BMI range for UK adults is 18.5 to 24.9 according to NHS guidance. However, if you're of South Asian, Chinese, Black African, or Black Caribbean heritage, the NHS recommends a slightly lower threshold of 18.5 to 22.9 due to higher health risks at the same BMI. Your BMI is calculated by dividing your weight in kilograms by your height in metres squared, and it's a useful screening tool to understand where your weight sits relative to your height. Use our free BMI calculator above to find your personal BMI instantly and see which category you fall into.
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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 main BMI categories for UK adults:
- Underweight: BMI below 18.5 — may indicate you need to gain weight or check for underlying health issues
- Healthy weight: BMI 18.5–24.9 — the normal range associated with lowest health risks
- Overweight: BMI 25.0–29.9 — increased risk of weight-related health conditions
- Obese (Class I): BMI 30.0–34.9 — significantly increased health risks including type 2 diabetes and cardiovascular disease
- Obese (Class II): BMI 35.0–39.9 — very high health risks
- Severely obese (Class III): BMI 40.0 and above — severe health risks requiring medical support
For people of South Asian, Chinese, Black African, or Black Caribbean backgrounds, the overweight threshold starts at BMI 23.0 and obesity starts at BMI 27.5, reflecting NICE guidance on ethnicity-adjusted risk. These lower thresholds are important because research shows these populations face higher risk of type 2 diabetes and heart disease at the same BMI as other groups.
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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.
NHS Weight Management Support And When To See Your GP
If your BMI falls outside the healthy range, the NHS recommends speaking to your GP, who can assess your individual health and discuss weight management options. The NHS follows a four-tier weight management pathway: tier 1 includes self-help tools and community programmes, tier 2 involves GP-led behaviour change support, tier 3 is specialist multidisciplinary weight management services (where prescription medications like Mounjaro or Wegovy may be considered), and tier 4 includes bariatric surgery for severe cases. Your GP can help you understand what's right for you. Remember that BMI has limitations — it doesn't distinguish between muscle and fat, so athletes may have a high BMI despite low body fat. Use our free weight converter to check your weight in different units (stone, kilograms, pounds), and track your progress with our free progress tracker if you're working towards a healthier weight.
- 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.
Is a BMI of 25 considered overweight in the UK?
Yes. According to NHS guidelines, a BMI of 25.0 to 29.9 is classified as overweight. However, if you're of South Asian, Chinese, Black African, or Black Caribbean heritage, the NHS recommends a lower overweight threshold starting at BMI 23.0. Your GP can discuss what this means for your individual health.
What's the difference between NHS BMI categories and other systems?
The NHS uses evidence-based categories aligned with NICE guidance and adjusted thresholds for different ethnicities. The standard categories (underweight, healthy, overweight, obese) are used globally, but the NHS specifically recognises that ethnicity affects health risk at the same BMI, so recommendations vary by background.
Can I have a high BMI and still be healthy?
BMI is a screening tool, not a diagnostic tool. Athletes and very muscular individuals may have a high BMI but low body fat. However, for most people, BMI outside the healthy range indicates increased health risks. Your GP can assess your individual health through other measures like waist circumference and blood pressure.
When should I speak to my GP about my BMI?
If your BMI is below 18.5 or above 25, or if you have concerns about your weight and health, it's worth discussing with your GP. They can assess whether your BMI reflects a genuine health risk or whether other factors are at play, and discuss support options if needed.
Are BMI ranges different for men and women?
No. The NHS BMI categories and thresholds are the same for men and women. However, healthy body fat percentages differ between sexes due to biological differences. BMI is a weight-to-height ratio that applies equally to all adults, though ethnicity-adjusted thresholds do apply for certain populations as recommended by NHS guidance.
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.