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 Normal BMI Range?
A normal BMI range in the UK is between 18.5 and 24.9 according to NHS guidelines. This is the healthy weight category for adults. Your BMI (body mass index) is calculated using your height and weight, and it helps your GP assess whether you're at a healthy weight for your body. Understanding where your BMI falls on the official scale is important for identifying any weight-related health risks. Use our free BMI calculator above to find your personal BMI instantly and see which category you fall into.
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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 Explained
The NHS BMI formula divides adults into five categories based on their height and weight:
- Underweight: BMI below 18.5 — may indicate insufficient weight for optimal health
- Healthy weight: BMI 18.5 to 24.9 — the normal BMI range associated with lower 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 elevated health risks
- Obese (Class II): BMI 35.0 to 39.9 — severe health complications more likely
- Severely obese (Class III): BMI 40.0 and above — very high risk requiring medical support
These BMI categories UK thresholds apply to most adults aged 18–65. However, the overweight BMI threshold is lower for people of South Asian, Chinese, Black African, or Black Caribbean heritage, reflecting their higher cardiovascular and diabetes risk at lower BMI levels. Your GP can help you understand what your BMI means for your individual health.
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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 doesn't distinguish between muscle and fat — athletes or very muscular people may have a high BMI but low body fat. It also doesn't account for where fat is stored; excess belly fat carries greater health risk than fat stored elsewhere. Your GP may assess additional measurements like waist circumference (over 94cm in men or 80cm in women indicates increased risk) alongside your BMI. Age, ethnicity, and medical history all matter too. Rather than relying on BMI alone, a holistic view of your health — including fitness level, diet quality, blood pressure, and cholesterol — gives the clearest picture. Use our free weight converter to compare your weight in different units, and speak with your GP about what a healthy weight means for you personally.
- 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 normal or healthy?
A healthy BMI is between 18.5 and 24.9 according to NHS guidelines. This range is associated with lower risk of weight-related health problems like type 2 diabetes and heart disease. However, BMI is just one measure — overall fitness, diet quality, and medical history also matter.
Is BMI the same for men and women?
Yes, the NHS BMI categories are the same for both men and women aged 18–65. However, individual health risks can vary based on body composition, where fat is stored, and personal medical history. Your GP can provide personalised guidance.
Are BMI ranges different for different ethnicities?
Yes. For people of South Asian, Chinese, Black African, or Black Caribbean heritage, the NHS recommends lower thresholds: healthy BMI is 18.5–22.9 and overweight starts at 23.0. This reflects their higher risk of diabetes and heart disease at lower BMI levels.
Why doesn't my healthy weight range match my BMI category?
BMI is based on height and weight alone — it doesn't account for muscle mass, bone density, or where fat is stored. Athletes may have high BMI but be very fit. Your GP can assess your individual healthy weight range considering your body composition and health goals.
Can I use BMI to check my child's weight?
No — children's BMI uses age and sex-specific growth charts, not adult categories. The NHS Healthy Weight Calculator has a section for children. Always speak with your GP or health visitor about a child's weight. ```
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.