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
Understanding Body Weights and Your Health
Body weight is one of the most important health indicators, but understanding what a healthy weight means for you personally requires more than just a number on the scales. Your weight influences your risk of type 2 diabetes, heart disease, and many other health conditions. According to NHS guidance, weight is best assessed using BMI alongside waist circumference and overall lifestyle factors. This UK health guide explains how body weight works, what healthy weight ranges mean, and how to assess whether your current weight puts you at health risk.
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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.
How Body Weight Affects Your Health
Body weight is a key health marker because excess weight increases your risk of serious health conditions. Being overweight or living with obesity is linked to type 2 diabetes (up to 80 times higher risk at severe obesity), cardiovascular disease, certain cancers (13 types linked to excess weight), obstructive sleep apnoea, and non-alcoholic fatty liver disease. However, weight alone doesn't tell the full story — where your body stores fat matters too. The NHS recommends assessing weight using BMI (body mass index) alongside waist circumference. Men with a waist over 102cm (40 inches) and women over 88cm (34.5 inches) have increased health risk, even if their BMI is in a healthy range.
Even modest weight loss can deliver meaningful health benefits. Losing just 5–10% of your body weight can reduce blood pressure, improve blood sugar control, lower cholesterol, ease joint pain, and reduce sleep apnoea severity. Use our free BMI calculator above to check where your current weight falls, and our weight converter to switch between kg, stone, and pounds.
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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.
Healthy Weight Ranges for UK Adults
The NHS defines healthy weight using BMI ranges. For most adults, a BMI between 18.5 and 24.9 is considered healthy. However, for people of South Asian, Chinese, Black African, or Black Caribbean heritage, the NHS recommends lower thresholds — a healthy BMI starts at 18.5 but drops to 22.9 instead of 24.9, because these groups face higher cardiovascular and diabetes risk at the same BMI levels. Your GP can assess whether your personal weight is healthy by considering your BMI, waist measurement, family history, and any weight-related health conditions you may have. It's important to remember that BMI doesn't distinguish between muscle and fat — athletes may have a high BMI but low body fat — so your GP's assessment is always more valuable than a calculator 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 considered a healthy body weight in the UK?
The NHS defines healthy weight using BMI (body mass index) of 18.5–24.9 for most adults. For South Asian, Chinese, Black African, or Caribbean heritage adults, the healthy range is 18.5–22.9. Waist circumference also matters — men should aim for under 94cm (37 inches), women under 80cm (31.5 inches). Your GP can give personalised guidance based on your health history.
How much does body weight affect disease risk?
Significantly. Obesity increases your risk of type 2 diabetes by up to 80 times, plus cardiovascular disease, 13 cancer types, sleep apnoea, and fatty liver disease. Conversely, even a 5–clinically studied weight loss can reduce blood pressure, improve blood sugar, lower cholesterol, ease joint pain, and improve sleep quality. Weight loss at a sustainable rate of 0.5–1kg per week is recommended by the NHS.
Why is waist circumference important alongside body weight?
Where you store fat matters more than total weight. Central obesity (fat around the belly) carries higher health risk than fat stored elsewhere. NHS guidance recommends measuring waist circumference alongside BMI. For men, over 94cm signals increased risk; over 102cm signals high risk. For women, over 80cm indicates increased risk; over 88cm indicates high risk.
Does body weight mean the same thing for everyone?
No. Healthy weight varies by height, age, sex, muscle mass, genetics, and ethnicity. BMI has limitations — it doesn't account for muscle, so athletes may have high BMI but low body fat. Your GP considers your full health picture, not just weight. Our free BMI calculator and weight converter help with initial assessment, but professional advice is always valuable.
How can I track whether my body weight is changing in the right way?
Track weight loss at 0.5–1kg per week for sustainable results. Weigh yourself weekly (same day, same time). Use our free progress tracker to log your journey. Remember — weight fluctuates daily due to water retention, so focus on the overall trend, not daily changes. Combine weight monitoring with how you feel and how your clothes fit.
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.