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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Understanding Weight Categories in the UK
Weight categories in the UK are determined by BMI (body mass index) and follow NHS guidelines that classify adults into specific health ranges. Your weight category helps you and your GP understand your current health risk and whether lifestyle changes or weight management support might be beneficial. Understanding where you fall within these categories is the first step towards informed health decisions, whether that's exploring nutrition, exercise, or consulting your healthcare provider about weight management options.
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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 Weight Categories and BMI Ranges
The NHS uses standardised BMI ranges to classify weight categories for UK adults. BMI is calculated by dividing your weight in kilograms by your height in metres squared. These categories help identify health risks associated with excess weight or being underweight.
- Underweight: BMI below 18.5 — may indicate nutritional concerns
- Healthy weight: BMI 18.5–24.9 — associated with lowest health risks
- Overweight: BMI 25.0–29.9 — increased risk of weight-related conditions
- Obese (Class I): BMI 30.0–34.9 — higher health risks
- Obese (Class II): BMI 35.0–39.9 — significant health concerns
- Severely obese (Class III): BMI 40.0 and above — substantial health risks
For adults of South Asian, Chinese, Black African, or Black Caribbean heritage, the NHS recommends lower thresholds because these groups face higher risk of type 2 diabetes and heart disease at lower BMI levels. For these populations, healthy weight is BMI 18.5–22.9, and overweight begins at 23.0.
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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.
Using Tools to Find Your Weight Category
Determining your weight category is straightforward using our free BMI calculator on this page — simply enter your height and current weight, and your BMI and category appear instantly. You can also use our weight converter to understand your weight in different units (kg, stone, or lbs), which helps when comparing your weight to UK health guidance. If you're working towards a healthy weight range, our GLP-1 weight loss calculator can help you explore potential outcomes with evidence-based weight management support. Remember that BMI is a useful screening tool, but it doesn't account for muscle mass, where fat is stored, or individual health circumstances — your GP can provide personalised advice about what your category means for your health.
- 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 healthy weight category in the UK?
According to NHS guidance, the healthy weight category for most UK adults is a BMI between 18.5 and 24.9. For people of South Asian, Chinese, Black African, or Black Caribbean heritage, the healthy range is 18.5 to 22.9 due to different health risk profiles at the same BMI. Use our BMI calculator to find your category.
Why are weight categories different for some ethnic groups?
Research shows that people from South Asian, Black African, Black Caribbean, and Chinese backgrounds have higher risk of type 2 diabetes, heart disease, and related conditions at lower BMI levels compared to white European populations. The NHS adjusted thresholds for these groups to better reflect their actual health risks.
Does weight category take into account muscle mass?
No — BMI doesn't distinguish between muscle and fat. Athletes or very muscular individuals may have a high BMI despite low body fat. Your GP can assess whether your weight category is personally appropriate by considering your overall health, fitness, and risk factors.
Can I move to a lower weight category safely?
Yes. The NHS recommends losing weight at a rate of 0.5–1 kg (1–2 lbs) per week for sustainable, safe results. This might involve dietary changes, increased physical activity, or in some cases, prescription weight management support. Your GP can discuss the safest approach for your individual circumstances.
What should I do if my weight category shows increased health risk?
Start by speaking to your GP, who can assess your overall health, discuss lifestyle changes like nutrition and exercise, and if appropriate, refer you to NHS weight management services. Even a 5–10% reduction in body weight can bring meaningful health benefits.
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.