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 High BMI?
A high BMI according to NHS guidelines is 30 or above, which falls into the obese category. Your BMI (body mass index) is a screening tool that compares your weight to your height to give a simple number that indicates whether you're at a healthy weight for your height. Understanding your BMI range is important because it can help identify potential health risks, though it's not the complete picture of your health. Use our free BMI calculator above to check your personal BMI instantly, or read on to understand what a high BMI means for you.
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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 Counts as High
According to NHS guidelines, BMI is divided into four main categories. A healthy BMI is between 18.5 and 24.9, which is the target range for most UK adults. An overweight BMI ranges from 25.0 to 29.9 — this is above the healthy range but not yet classified as obese. A high BMI or obese BMI starts at 30.0 and above.
Within the obese category itself, there are further subdivisions: Class I obesity is 30.0–34.9, Class II obesity is 35.0–39.9, and Class III (severe obesity) is 40.0 or above. These distinctions matter because they help your GP assess your individual health risk.
To calculate your own BMI using the standard BMI formula, divide your weight in kilograms by your height in metres squared. For example, someone weighing 90kg and 1.75m tall would have a BMI of approximately 29.4 (overweight) or 91kg would be 29.6 (high, at the threshold of obesity). Our weight converter can help you check your weight in the right units if needed.
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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
While BMI is a useful screening tool, it has important limitations. A high BMI doesn't always mean poor health — athletes and very muscular people may have a high BMI but low body fat percentage. Conversely, someone with a "healthy" BMI might still have excess fat around their organs. BMI also doesn't account for where your weight is stored; fat around the abdomen is more linked to health risks than fat elsewhere.
That's why the NHS also recommends measuring waist circumference. For men, a waist over 94cm (37 inches) indicates increased health risk, and over 102cm (40 inches) indicates high risk. For women, the thresholds are 80cm (31.5 inches) and 88cm (34.5 inches). Your GP can give you personalised health advice based on your complete picture — not just your BMI number 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 BMI number is considered high?
According to NHS guidelines, a BMI of 30 or above is classified as obese, which is considered high. A BMI between 25 and 29.9 is overweight, and 18.5 to 24.9 is healthy. If you fall into the 30+ range, your GP may discuss lifestyle changes or other health support with you.
Is a BMI of 30 high for everyone?
For most UK adults, yes, 30 is the obesity threshold. However, the NHS recommends lower thresholds for adults of South Asian, Chinese, Black African, or Black Caribbean heritage — for these groups, the obese category starts at 27.5. Your GP can advise what's appropriate for your individual circumstances and ethnicity.
Does a high BMI always mean I'm unhealthy?
A high BMI is a screening indicator, not a diagnosis of illness. It suggests increased health risk, but individual health depends on many factors including fitness, diet, sleep, stress, and family history. Waist circumference and other measures also matter. Your GP can assess your overall health beyond your BMI number.
What should I do if my BMI is high?
Speaking with your GP is a good first step. They can assess your overall health and discuss options like lifestyle changes, increased physical activity, and dietary adjustments. In some cases, NHS-based weight management programmes or specialist services may be available in your area. The NHS Weight Loss Plan is also free to use online.
How accurate is BMI compared to body fat percentage?
BMI is quick and useful for screening large populations, but body fat percentage and waist measurement are more detailed. BMI can't distinguish between muscle and fat, so very fit or athletic people may have a "high" BMI despite being healthy. A complete health assessment uses multiple measures, not just BMI alone.
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.