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 Regular BMI Range?
The regular or "healthy" BMI range according to NHS guidelines is between 18.5 and 24.9. This range indicates a weight that is considered healthy for most adults based on their height. However, BMI is just one tool for assessing health — it doesn't account for muscle mass, bone density, or where fat is stored on your body. Your GP can help you understand what your individual BMI means for your health, especially if you have weight-related health conditions. Use our free BMI calculator above to find your personal BMI instantly.
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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 BMI range system divides adults into five main categories. A regular, healthy BMI falls between 18.5 and 24.9 — this is the range where most health risks related to weight are lowest. Below 18.5 is classified as underweight, which may indicate insufficient nutrition or other health concerns. Between 25.0 and 29.9 is classed as overweight, and BMI of 30.0 and above is classified as obese. Within the obese category, there are further subdivisions: Class I (30–34.9), Class II (35–39.9), and Class III (40 and above, also called severely obese). For people of South Asian, Chinese, Black African, or Black Caribbean heritage, the NHS recommends lower BMI thresholds — a healthy range starts at 18.5 but caps at 22.9, because these populations face higher cardiovascular and diabetes risk at the same BMI as white European populations. Understanding where you fall within this BMI formula breakdown helps your GP assess your individual health risk.
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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 to Consider
Although the regular BMI range is a useful screening tool, it has important BMI limitations. BMI cannot distinguish between muscle and fat — athletes or very fit people may have a high BMI but low body fat percentage. Age also affects BMI accuracy; elderly people often have lower muscle mass and may benefit from slightly higher BMI. Pregnancy, certain medications, and medical conditions can all affect weight independently of health. For a complete health picture, your GP may also assess your waist circumference: above 94cm (37 inches) for men or 80cm (31.5 inches) for women indicates increased health risk, even within a regular BMI. Combining BMI with these additional measures gives a more accurate view of your overall health status.
- 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 BMI is considered regular or normal?
The regular BMI range is 18.5 to 24.9 according to NHS guidelines. This range indicates a healthy weight for most adults. However, for people of South Asian, Chinese, or Black African heritage, the upper limit is 22.9 instead of 24.9, as these groups face higher health risks at higher BMI levels.
How do I calculate my BMI to see if I'm in the regular range?
Use our free BMI calculator above — simply enter your height and weight in kg or stone and pounds, and it calculates your BMI instantly. Alternatively, use the formula: weight (kg) ÷ height (m)². If you're unsure about the calculation, our tool removes the guesswork.
Is a regular BMI range the same as a healthy weight?
Largely yes, but not perfectly. A regular BMI range suggests a weight associated with lower health risks for most adults. However, BMI doesn't account for muscle, bone density, or fat distribution. Your GP can advise whether your specific weight is healthy given your age, fitness level, medical history, and lifestyle.
What if my BMI is just outside the regular range?
If your BMI is 25–29.9 (overweight) or slightly under 18.5 (underweight), discuss this with your GP rather than assuming you need to change your weight immediately. Health involves many factors beyond BMI. Your GP can assess whether your weight poses health risks and suggest safe, sustainable changes if needed.
Why is the regular BMI range different for different ethnic groups?
Research shows that people of South Asian, Chinese, Black African, and Black Caribbean backgrounds develop type 2 diabetes and heart disease at lower BMI levels than white European populations. The NHS therefore recommends lower BMI thresholds for these groups to catch health risks earlier and support better prevention.
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.