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 Healthy BMI Range?
According to NHS guidelines, a normal healthy BMI for UK adults is between 18.5 and 24.9. This range indicates a weight that is generally associated with the lowest health risks for most adults. However, BMI is a screening tool only and doesn't account for muscle mass, bone density, or where fat is stored on your body. Your GP can provide personalised advice about what your individual BMI means for your health. Use our free BMI calculator above to check your personal BMI in seconds.
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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 Healthy Weight Ranges
The BMI formula is weight (kg) divided by height in metres squared. According to the NHS BMI classification system, here are the standard BMI categories UK:
- Underweight: BMI below 18.5 — may indicate insufficient calorie intake or nutritional deficiency
- Healthy weight: BMI 18.5 to 24.9 — associated with the lowest health risks
- Overweight: BMI 25.0 to 29.9 — increased risk of weight-related health conditions
- Obese (Class I): BMI 30.0 to 34.9 — significantly higher health risks
- Obese (Class II): BMI 35.0 to 39.9 — substantially elevated health risks
- Severely obese (Class III): BMI 40.0 and above — very high health risks
For adults of South Asian, Chinese, Black African, or Black Caribbean heritage, the NHS recommends lower healthy BMI thresholds: healthy weight is BMI 18.5 to 22.9, as these groups face higher cardiovascular and diabetes risk at standard 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.
BMI Limitations and What Else Matters
BMI limitations are important to understand. BMI does not distinguish between muscle and fat — athletes may have a high BMI but low body fat percentage. It also doesn't account for age, bone density, or where fat is stored. A high waist circumference is a strong independent risk factor for cardiovascular disease and type 2 diabetes, regardless of BMI. The overweight BMI threshold may not reflect true health risk in all individuals. For a complete health picture, consider your waist measurement (over 94cm in men or 80cm in women indicates increased risk), activity level, and family history. Your GP can assess your overall health risk beyond BMI alone.
- 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 the normal healthy BMI range in the UK?
The NHS defines a healthy BMI as 18.5 to 24.9 for most UK adults. For adults of South Asian, Chinese, Black African, or Black Caribbean heritage, the healthy range is 18.5 to 22.9 due to higher health risks at higher BMI levels in these populations.
How do I calculate my BMI?
Divide your weight in kilograms by your height in metres squared. For example, someone weighing 70kg and 1.73m tall would have a BMI of 70 ÷ (1.73 × 1.73) = 23.4. Use the free BMI calculator on this page for gradual improvement.
Is a BMI of 25 considered overweight?
Yes, a BMI of 25 falls into the overweight category (25.0–29.9). While not yet in the obese range, the NHS recommends lifestyle changes to prevent further weight gain and reduce health risks.
Why are the BMI ranges different for some ethnic groups?
Research shows that South Asian, Chinese, Black African, and Black Caribbean adults have higher risks of type 2 diabetes and heart disease at lower BMI levels than European populations. The NHS adjusted thresholds reflect this increased risk.
Can BMI be inaccurate?
Yes. BMI doesn't account for muscle mass, so very muscular or athletic individuals may have a high BMI despite low body fat. Age, bone density, and fat distribution also affect health risk. Waist circumference and GP assessment provide additional important information.
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.