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
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What Is The Average BMI In The UK?
The average BMI among UK adults is approximately 27.4 for women and 27.9 for men, according to the latest Office for National Statistics data. This means the average adult in the UK falls into the overweight category according to NHS guidelines. However, average does not mean healthy — understanding what the NHS considers a healthy BMI, how it's calculated, and what it means for your individual health is important for making informed decisions about your wellbeing. Use our free BMI calculator above to check your personal BMI instantly and see how it compares to NHS healthy weight ranges.
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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 BMI Categories And What They Mean
The NHS classifies BMI into five main categories to help assess weight-related health risk:
- Underweight: BMI below 18.5 — may indicate inadequate nutrition or underlying health conditions
- Healthy weight: BMI 18.5 to 24.9 — associated with lowest risk of weight-related health problems
- Overweight: BMI 25.0 to 29.9 — increased risk of high blood pressure, high cholesterol, and type 2 diabetes
- Obese (Class I): BMI 30.0 to 34.9 — substantially increased health risk
- Severely obese (Class III): BMI 40.0 and above — significantly elevated risk of serious health conditions
Since the UK average BMI of 27–28 falls in the overweight category, this reflects a significant public health challenge. NICE guidance emphasises that even modest weight loss of 5–10% can meaningfully reduce health risks and improve conditions like type 2 diabetes and high blood pressure. The NHS BMI formula used is weight (kg) ÷ height (m)², applicable to all adults aged 18 and over.
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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 Support And When To Seek Help
The NHS offers a four-tier weight management pathway to support adults concerned about their weight. Tier 1 includes self-help resources and the free NHS Weight Loss Plan. If your BMI is 25 or above with weight-related health conditions, or 30 or above regardless of health conditions, your GP can refer you to tier 2 or tier 3 specialist services. Tier 3 services provide structured behaviour change programmes, and some may prescribe prescription weight loss medications. Tier 4 specialist bariatric surgery is available for severe obesity with significant complications. Your GP can assess your individual risk and discuss what support is right for you — BMI is a screening tool, not a diagnosis. Convert your weight between kg, stone, and lbs using the free weight converter on this page to track your measurements in whichever format suits you best.
- 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 an average BMI of 27 considered overweight?
Yes. According to NHS guidelines, a BMI of 27 falls in the overweight category (25.0–29.9). The UK average BMI of approximately 27–28 reflects that most adults are classified as overweight, even though it is statistically average. Average does not mean healthy — the NHS healthy weight range remains 18.5–24.9 BMI.
What BMI does the NHS recommend as healthy?
The NHS recommends a healthy BMI of 18.5 to 24.9 for most adults. For people of South Asian, Chinese, Black African, or Black Caribbean heritage, the NHS recommends a slightly lower healthy range of 18.5 to 22.9, as these populations face higher cardiovascular and diabetes risk at the same BMI as other groups.
How is BMI calculated, and what are its limitations?
BMI is calculated by dividing weight in kilograms by height in metres squared (BMI = kg ÷ m²). Key limitations include: it does not distinguish between muscle and fat (athletes may have high BMI with low body fat), it does not account for where fat is stored (waist circumference also matters), and it may be less accurate for elderly people or during pregnancy. BMI is a screening tool, not a diagnosis.
Should I be concerned if my BMI is above the NHS healthy range?
If your BMI is 25 or above, particularly if you have weight-related health conditions like type 2 diabetes or high blood pressure, it's worth discussing with your GP. Even a 5–10% reduction in body weight can reduce health risk. Your GP can assess your individual circumstances, family history, and health conditions to advise on appropriate next steps.
What does the NHS recommend if I want to lose weight?
The NHS recommends losing weight at a sustainable rate of 0.5–1 kg per week through a combination of dietary changes and increased physical activity. Start with the free NHS Weight Loss Plan, discuss with your GP, and if eligible for tier 2 or tier 3 services, ask about referral. For some adults, prescription weight loss support may be appropriate following clinical assessment.
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.